| osteopontin expression in mammary gland development and tumorigenesis. | osteopontin (opn) is a secreted phosphoprotein that binds to cells via an arg-gly-asp sequence and to mineralized surfaces. the protein can mediate cell adhesion and is strongly implicated in transformation and tumorigenesis. we have examined the expression pattern of opn in mouse mammary glands at different stages of postnatal development. whereas opn is expressed at low-to-moderate levels in mammary glands from virgin and pregnant mice, the levels of opn mrna are extremely high in the lactatin ... | 1997 | 9342184 |
| the regulation of mammary prolactin receptor metabolism by a retroviral envelope protein. | in a previous study, infection with the mouse mammary tumor virus (mmtv) was shown to increase the sensitivity of the mammary epithelium toward prolactin (prl); furthermore, this effect could be mimicked by the binding of the mmtv envelope protein (gp52) to its cell receptor. the present work has investigated the possibility that gp52-induced changes in the prl receptor (prlr) were responsible for this phenomenon. in vitro, gp52 doubled the prlr concentration in the plasmalemma of mammary epithe ... | 1997 | 9343305 |
| chromosomal double-strand breaks induce gene conversion at high frequency in mammalian cells. | double-strand breaks (dsbs) stimulate chromosomal and extrachromosomal recombination and gene targeting. transcription also stimulates spontaneous recombination by an unknown mechanism. we used saccharomyces cerevisiae i-scei to stimulate recombination between neo direct repeats in chinese hamster ovary (cho) cell chromosomal dna. one neo allele was controlled by the dexamethasone-inducible mouse mammary tumor virus promoter and inactivated by an insertion containing an i-scei site at which dsbs ... | 1997 | 9343400 |
| glucocorticoids stimulate growth of human papillomavirus type 16 (hpv16)-immortalized human keratinocytes and support hpv16-mediated immortalization without affecting the levels of hpv16 e6/e7 mrna. | we investigated the effects of the glucocorticoids hydrocortisone and dexamethasone on human papillomavirus type 16 (hpv16)-mediated human cell carcinogenesis using normal human keratinocytes (hkc) and hkc immortalized by transfection with hpv16 dna (hkc/hpv16). normal hkc did not require glucocorticoids for proliferation. in contrast, growth of early passage hkc/hpv16 strictly required these hormones, although glucocorticoid dependence became less stringent during in vitro progression. glucocor ... | 1997 | 9344611 |
| targeted expression of a dominant negative epidermal growth factor receptor in the mammary gland of transgenic mice inhibits pubertal mammary duct development. | the epidermal growth factor (egf) system has been thought to play an important role in normal mammary development and carcinogenesis. to study the role of the egf receptor (egfr) in mammary development, we developed a transgenic mouse model in which a c-terminal truncated mouse egfr (egfr-tr) was expressed in the mouse mammary epithelium under the control of the mouse mammary tumor virus long terminal repeat. the egfr-tr lacks most of the cytoplasmic domain of the receptor, including the entire ... | 1997 | 9369445 |
| identification of a mmtv insertion mutation within the coding region of the fgf-3 protooncogene. | the fgf-3 protooncogene (previously called int-2) is a target of proviral insertion mutations in mammary tumors induced by the mouse mammary tumor virus (mmtv). these insertion mutations result in the transcriptional activation of fgf-3, which is not normally expressed in the adult mammary gland. previous mapping studies of numerous fgf-3 insertion mutations have failed to reveal any provirus integrations within the gene coding region. this finding is consistent with the hypothesis that oncogene ... | 1997 | 9375020 |
| real-time monitoring of estrogen-regulated gene expression in single, living breast cancer cells: a new paradigm for the study of molecular dynamics. | elucidation of the molecular mechanisms underlying the development and progression of breast cancer has been hindered by two considerations. first, mammary tumor cells exhibit a considerable degree of morphological and functional heterogeneity. thus, the conventional strategy of measuring a population response may not provide an accurate reflection of the behavior of the functional unit: an individual cell. second, important regulatory events are generally separated in time, yet the strategies w ... | 1997 | 9377549 |
| steroid-independent translocation of the glucocorticoid receptor by the antidepressant desipramine. | the glucocorticoid receptor (gr) is a ligand-regulated transcription factor that in its unactivated form resides primarily in the cytoplasm. after being bound by steroid, the gr undergoes a conformational change and translocates to the nucleus, where it influences gene transcription. because the gr mediates negative feedback exerted by circulating glucocorticoid hormones on the hypothalamic-pituitary-adrenal (hpa) axis, it has been hypothesized that abnormalities in gr expression and/or function ... | 1997 | 9380019 |
| trans-retinoic acid and glucocorticoids synergistically induce transcription from the mouse mammary tumor virus promoter in human embryonic kidney cells. | human embryonic kidney (k293) cells transfected with a mouse mammary tumor virus (mmtv) promoter-luciferase reporter construct (phh-luc) were utilized to investigate the potential effects of trans-retinoic acid (tra), either by itself or in combination with glucocorticoid (gc) hormones, on a well-characterized, gc-sensitive transcriptional response. tra or the synthetic gc hormone dexamethasone induced transcription from the mmtv promoter in a dose-dependent manner, with 1 micromol tra and 1 mic ... | 1997 | 9393948 |
| wnt-10b directs hypermorphic development and transformation in mammary glands of male and female mice. | wnt-10b is expressed during the formation of the mammary rudiment in mouse embryos and its expression continues through puberty when the mammary ductal pattern is established under control of ovarian steroids. recently, viral activation of the wnt-10b locus has linked its overexpression to mammary tumor formation, suggesting a role for wnt-10b in patterning and growth-regulation of the mammary gland. to test this notion, we created lines of transgenic mice that express elevated levels of wnt-10b ... | 1997 | 9393971 |
| influence of retinoic acid on the differentiation pathway of t cells in the thymus. | this study investigated the ability of retinoic acid (ra) to influence t cell differentiation. all-trans-ra had marked effects on t cell differentiation in murine fetal thymic organ cultures (ftocs). the time course of the effect of all-trans-ra in ftoc of day 14 c57bl/6 embryos revealed a twofold increase in the frequency of cd4 single-positive (sp) cells and a high level of cd3-bearing cells (cd3high cells) at a later stage of t cell development. at an earlier stage, all-trans-ra induced a two ... | 1997 | 9398402 |
| the chromosome location of the human homolog of the mouse mammary tumor-associated gene int6 and its status in human breast carcinomas. | the int6 gene is a common integration site for the mouse mammary tumor virus in mouse mammary tumors. we have determined that the human homolog of int6 is located on chromosome region 8q22-q23. a processed int6 pseudogene is located on chromosome 6q. int6 is composed of 13 exons that span 45 kb of genomic dna. the deduced amino acid sequence of the gene product is identical to the mouse protein and contains three potential translation start signals. we have examined 100 primary breast carcinoma ... | 1997 | 9403073 |
| transgenic mice overexpressing a dominant-negative mutant type ii transforming growth factor beta receptor show enhanced tumorigenesis in the mammary gland and lung in response to the carcinogen 7,12-dimethylbenz-[a]-anthracene. | to test the hypothesis that the transforming growth factor-beta (tgf-beta) system has tumor suppressor activity in the mammary gland, we have generated transgenic mice overexpressing a dominant-negative mutant form of the type ii tgf-beta receptor, under the control of the mouse mammary tumor virus-long terminal repeat. high-level expression of the transgene was observed in the mammary and salivary glands, with lower expression in the lung, spleen, and testis. older nulliparous transgenic mice ( ... | 1997 | 9407968 |
| a farnesyltransferase inhibitor induces tumor regression in transgenic mice harboring multiple oncogenic mutations by mediating alterations in both cell cycle control and apoptosis. | the farnesyltransferase inhibitor l-744,832 selectively blocks the transformed phenotype of cultured cells expressing a mutated h-ras gene and induces dramatic regression of mammary and salivary carcinomas in mouse mammary tumor virus (mmtv)-v-ha-ras transgenic mice. to better understand how the farnesyltransferase inhibitors might be used in the treatment of human tumors, we have further explored the mechanisms by which l-744,832 induces tumor regression in a variety of transgenic mouse tumor m ... | 1998 | 9418856 |
| the tripartite leader sequence of subgroup c adenovirus major late mrnas can increase the efficiency of mrna export. | the subgroup c human adenoviruses induce selective export of newly synthesized viral mrna from the nucleus to the cytoplasm, with concomitant inhibition of export of the majority of cellular mrna species. such posttranscriptional regulation of viral and cellular gene expression in infected cells requires viral e1b and e4 proteins. to facilitate the investigation of parameters that govern selective export in adenovirus-infected cells, we constructed a marked human beta-actin minigene under the co ... | 1998 | 9420219 |
| substitution of ala564 in the first zinc cluster of the deoxyribonucleic acid (dna)-binding domain of the androgen receptor by asp, asn, or leu exerts differential effects on dna binding. | in the androgen receptor of a patient with androgen insensitivity, the alanine residue at position 564 in the first zinc cluster of the dna-binding domain was substituted by aspartic acid. in other members of the steroid receptor family, either valine or alanine is present at the corresponding position, suggesting the importance of a neutral amino acid residue at this site. the mutant receptor was transcriptionally inactive, which corresponded to the absence of specific dna binding in gel retard ... | 1998 | 9421404 |
| two groups of endogenous mmtv related retroviral env transcripts expressed in human tissues. | the human genome contains at least 50 copies of the human endogenous retrovirus k (herv-k) family which is related to the mouse mammary tumor virus (mmtv). some members have been shown to be transcriptionally active and to have large open reading frames. using the rt-pcr method we have investigated the herv-k env transcription pattern in several malignant tissues and in peripheral blood mononuclear cells pbmcs). samples were derived from chronic myelogenous leukemia (cml), breast cancer, colon c ... | 1997 | 9421877 |
| antiprogestins mediate differential effects on glucocorticoid receptor remodeling of chromatin structure. | we examined the mechanism(s) by which the progesterone receptor (pr) is able to inhibit glucocorticoid receptor (gr) activation from the mouse mammary tumor virus (mmtv) promoter in vivo. using specific hormone antagonists, we demonstrate that the pr complexed with an type ii antiprogestin blocks glucocorticoid-induced activation of the mmtv promoter. however, when complexed with a type i antiprogestin the pr is unable to block glucocorticoid-induced activation. pr repression of gr activity resu ... | 1998 | 9422784 |
| functional analysis of mouse keratin 8 in polyoma middle t-induced mammary gland tumours. | keratin 8 and 18 are commonly used as tumorigenic markers for various types of carcinomas. they are known to be involved in cell migration, cell invasiveness, plasminogen activity and drug and radiation resistance. to ascertain a potential function for simple epithelium keratins in mammary adenocarcinoma in vivo, keratin-8-deficient mice (mk8) were mated with transgenic mice carrying the middle t oncogene driven by the mmtv promoter. the resulting mk8 knockout and control progeny carrying the mi ... | 1997 | 9423286 |
| secondary structures and starvation-induced frameshifting. | we have examined the effect of a downstream secondary structure (the stem-loop sequence found downstream on the mmtv gag-pro frameshift site) on frameshifting at a bacterial shifty site (u uuc aua) that responds strongly to a isoleucine-trna limitation. our findings are as follows: (i) the downstream stem-loop has little effect on frameshifting in growing, unstarved cells; (ii) the stem-loop increases the frameshifting effect of isoleucine-trna limitation about fourfold, and this synergism is ma ... | 1997 | 9427404 |
| inducible expression of p21waf-1/cip-1/sdi-1 from a promoter conversion retroviral vector. | constitutive, high-level expression of the potentially therapeutic waf-1/cip-1/sdi-1 gene is incompatible with cell growth. a promoter conversion retroviral vector carrying the waf-1/cip-1/sdi-1 gene under the transcriptional control of the glucocorticoid inducible promoter of mouse mammary tumor virus was used to infect human bladder carcinoma or feline kidney cells. reduced cell growth due to a greater proportion of cells being in the g0/g1 phase of the cell cycle was observed when waf-1/cip-1 ... | 1997 | 9428612 |
| highly biased cdr3 usage in restricted sets of beta chain variable regions during viral superantigen 9 response. | superantigens encoded by the mouse mammary tumor virus can stimulate a large proportion of t cells through interaction with germline-encoded regions of the t cell receptor beta chain like the hypervariable region 4 (hv4) loop. however, several lines of evidence suggest that somatically generated determinants in the cdr3 region might influence superantigen responses. we stimulated t cells from donors differing at the bv6s7 allele with vsag9 to assess the nature and structure of the t cell recepto ... | 1998 | 9432983 |
| hormone regulation of bovine leukemia virus via the long terminal repeat. | the hormone regulation of viruses has been of great interest since the discovery of glucocorticoid stimulation of mouse mammary tumor virus via a hormone response element in the viral long terminal repeat (ltr) promoter region. this report describes the investigation of the hormone responsiveness of bovine leukemia virus (blv), an oncogenic retrovirus that infects dairy and beef cattle worldwide. it is a member of the human t cell leukemia (htlv)/blv group of retroviruses, which encode a protein ... | 1997 | 9434716 |
| chromosomal localization of acquired mmtv proviral integration sites in t-cell lymphomas. | | 1998 | 9434954 |
| a polymorphism in the glucocorticoid receptor gene may be associated with and increased sensitivity to glucocorticoids in vivo. | we investigated whether a polymorphism at nucleotide position 1220, resulting in an asparagine-to-serine change at codon 363 in the glucocorticoid receptor (gr) gene is associated with an altered sensitivity to glucocorticoids. in a group of 216 elderly persons, 13 heterozygotes for the n363s polymorphism were identified by pcr/single strand conformation polymorphism analysis. in 2 dexamethasone (dex) suppression tests (dsts), using 1 and 0.25 mg dex, the circulating cortisol and insulin concent ... | 1998 | 9435432 |
| a preliminary analysis of antineoplastic activity of parvovirus mvmp ns-1 proteins. | human gastric cancer mkn-45 cells were transfected with pulb 3238, a plasmid carrying mvmp ns-1 gene with its original p4 promoter replaced by the glucocorticoid inducible promoter mmtv-ltr. after the integration and expression of ns-1 gene, some of the transfectants died, while others remained alive, but the growth features of survived cells were changed. for further study on the antineoplastic function of parvoviral ns-1 protein in vivo, transgenic mice carrying ns-1 genes were established by ... | 1997 | 9444400 |
| construction and characterization of a hybrid mouse mammary tumor virus/murine leukemia virus-based retroviral vector. | mouse mammary tumor virus (mmtv)-based vectors are characterized by low titers. in an effort to transfer mmtv-specific regulation of gene expression to a more efficient murine leukemia virus (mlv) vector, we have replaced the complete 3' u3 region of mlv with the complete u3 region of mmtv. virus titers were not significantly affected by this modification, there was no impairment of reverse transcription and integration, and after infection of cells, the mmtv promoter is duplicated and transloca ... | 1998 | 9445081 |
| reverse transcriptase of mouse mammary tumour virus: expression in bacteria, purification and biochemical characterization. | we have constructed a plasmid that induces in bacteria the synthesis of an enzymically active reverse transcriptase (rt) of mouse mammary tumour virus (mmtv), a retrovirus with a typical b-type morphology. the highest catalytic activity was detected only when 27 residues from the c-terminus of the protease were included in the n-terminus of the recombinant rt, after an extra deoxyadenosine was added between the pro and pol genes to overcome the -1 frameshift event (which occurs naturally in viru ... | 1998 | 9445385 |
| overexpression of the matrix metalloproteinase matrilysin results in premature mammary gland differentiation and male infertility. | to examine the role of matrilysin (mat), an epithelial cell-specific matrix metalloproteinase, in the normal development and function of reproductive tissues, we generated transgenic animals that overexpress mat in several reproductive organs. three distinct forms of human mat (wild-type, active, and inactive) were placed under the control of the murine mammary tumor virus promoter/enhancer. although wild-type, active, and inactive forms of the human mat protein could be produced in an in vitro ... | 1998 | 9450965 |
| antibodies to the c-terminal dipeptide of mouse mammary tumor virus [mmtv(sw)] superantigen effectively inhibit t-cell activation in vivo. | balb/c mice were immunized against the 19 c-terminal amino acids of the mouse mammary tumour virus [mmtv(sw)] superantigen, either actively with the recombinant orf19 protein or passively by subcutaneous implantation of 6e1.8 hybridoma cells. protection against the mmtv(sw) superantigen-induced activation of specific t cells was obtained in both immunizations. whereas the monoclonal antibody provided complete protection, similar antibody titres showed less effective protection in actively immuni ... | 1998 | 9460923 |
| cross talk between t and b cells generates b antigen-presenting cells able to induce inositol phosphate production in t cells responding to mls(a) superantigens. | previous studies showed that activation of cd4+ t cells with mouse mammary tumor virus-encoded mls(a) superantigens induces strong proliferative responses and interleukin-2 production but fails to elicit typical early t cell receptor (tcr)-mediated signal transduction events, such as hydrolysis of polyphosphoinositides (pi) or an increase in intracellular calcium. here we show that the failure of mls(a) antigen to activate pi hydrolysis applies when resting b cells are used as antigen-presenting ... | 1997 | 9464813 |
| positioning and stability of nucleosomes on mmtv 3'ltr sequences. | uniquely positioned nucleosomes were mapped in vitro on mouse mammary tumor 3' long terminal repeat (mmtv 3'ltr) dna at base-pair resolution. nucleosome a assembly was strongly favored over nucleosome b, and heating of each as a mononucleosome caused migration to the ends of the dna fragment at a unique rate. taken together with dna sequence analysis, this suggests why mmtv 3'ltv nucleosome positions reported upstream of vector-derived sequences conflict and also how flanking genomic sequences c ... | 1998 | 9466921 |
| tumour therapy in mice using adenovirus vectors expressing human tnfa. | induction of systemic toxicity is a major factor limiting the use of tnfa in tumour therapy. the local expression of tnfa from ad vector infected tumour cells, might result in reduced systemic toxicity and induce an enhanced local antitumour response. two adenoviral vectors expressing human tnfa were constructed for use in tumour immunotherapy, one utilizing the hcmv promoter (ad-hcmv-tnf) and the second utilizing the mcmv promoter (ad-mcmv-tnf). both vectors induced the secretion of htnfa from ... | 1998 | 9472086 |
| from rna hairpins to kisses to pseudoknots. | formation of rna hairpins presumably initiate the folding of an rna into its biologically functional form. the stems of the hairpin loops grow to produce a-form helices interrupted by internal loops and bulges. the loops then interact with metal ions and with other loops and bulges to finish folding the rna into its native biological state. the three-dimensional structures of several of these secondary and tertiary motifs have been determined by nuclear magnetic resonance. | 1997 | 9478203 |
| mouse mammary tumor virus and its interaction with the immune system. | mouse mammary tumor virus (mmtv) is a retrovirus that is transmitted through milk to offspring. gut-associated b cells are the first cells to be infected during virus transmission, and these cells present a virus-encoded superantigen to cognate t cells. this allows mmtv to replicate and amplify in activated lymphocytes and ultimately results in virus transmission to the mammary epithelial cells. because the superantigen has profound effects on the t cell repertoire and because mmtv replicates in ... | 1998 | 9479582 |
| synergistic enhancement of prb-mediated ru486 and r5020 agonist activities through cyclic adenosine 3',5'-monophosphate represents a delayed primary response. | activators of protein kinase a have been shown to affect the transactivation potential of progestins and antiprogestins. to analyze the mechanisms and factors involved, we have created hela and cv1 cell clones stably expressing isoform b of progesterone receptor. in the hela cell background, the progesterone antagonist ru486 significantly induces progesterone-regulatable reporter genes, and this agonistic effect is synergistically enhanced by elevating camp or through overexpression of protein k ... | 1998 | 9482668 |
| prolonged glucocorticoid exposure dephosphorylates histone h1 and inactivates the mmtv promoter. | glucocorticoids rapidly induce transcription from the mouse mammary tumour virus (mmtv) promoter via a glucocorticoid receptor (gr)-mediated chromatin disruption event. this remodelling of chromatin is transient such that upon prolonged exposure to hormone the promoter becomes refractory to glucocorticoids. we demonstrate that this refractory state requires the continual presence of hormone and can be reversed by its removal. our experiments show that the promoter is inactivated via a mechanism ... | 1998 | 9482742 |
| a full-length notch1 allele is dispensable for transformation associated with a provirally activated truncated notch1 allele in moloney mulv-infected mmtv(d)/myc transgenic mice. | the notch1 gene was previously found to be targetted by provirus insertion in a high proportion of t-cell lymphomas arising in moloney mulv-inoculated mmtv(d)/myc transgenic mice. proviral activation of notch1 was associated with overexpression of truncated notch1, deleted of the sequences coding for the extracellular domain. the high levels of truncated notch1 rna and proteins in these tumors are thought to be involved in the oncogenic transformation. however, in addition to these truncated rna ... | 1998 | 9484841 |
| regulation of na-k-atpase gene expression by hyperoxia in mdck cells. | na-k-atpase plays a central role in a variety of physiological processes, including ion transport and regulation of cell volume. our previous data showed that hyperoxia increased the expression of na-k-atpase alpha 1 and beta 1 mrna in lung type ii cells. we similarly show that hyperoxia (> or = 95% o2 for 24-48 h) increased steady-state mrna levels in both na-k-atpase subunits in madin-darby canine kidney (mdck) cells. the mechanism of gene regulation by hyperoxia was assessed. stability of the ... | 1998 | 9486124 |
| mutational analysis of the rna pseudoknot involved in efficient ribosomal frameshifting in simian retrovirus-1. | mutational effects on frameshifting efficiency of the rna pseudoknot involved in ribosomal frameshifting in simian retrovirus-1 (srv-1) have been investigated. the primary sequence and the proposed secondary structure of the srv-1 pseudoknot are similar to those of other efficient frameshifting pseudoknots in mouse mammary tumor virus (mmtv) and feline immunodeficiency virus (fiv), where an unpaired adenine nucleotide intercalates between stem 1 and stem 2. in srv-1 pseudoknot, the adenine nucle ... | 1998 | 9490779 |
| interaction between a semisynthetic diet and indole-3-carbinol on mammary tumor incidence in balb/cfc3h mice. | this paper extends prior studies on the chemoprotective effect of indole-3-carbinol (i3c) on mammary and endometrial tumors in rodent models and focuses on the interplay between standard laboratory chow (purina lab chow 5001), a high omega 6 fatty acid diet (ain76a), and i3c on the incidence of mouse mammary tumor virus-induced (mmtv) mammary tumors in mice. while the protective effect of i3c was observed in mice maintained on the ain76a diet from conception, a marked decrease in tumor incidence ... | 1997 | 9494529 |
| nucleocapsid and matrix protein contributions to selective human immunodeficiency virus type 1 genomic rna packaging. | the nucleocapsid protein (nc) of retroviruses plays a major role in genomic rna packaging, and some evidence has implicated the matrix protein (ma) of certain retroviruses in viral rna binding. to further investigate the role of nc in the selective recognition of genomic viral rna and to address the potential contribution of ma in this process, we constructed chimeric and deletion human immunodeficiency virus type 1 (hiv-1) mutants that alter the nc or ma protein. both hiv and mouse mammary tumo ... | 1998 | 9499052 |
| position-independent expression of a human nerve growth factor-luciferase reporter gene cloned on a yeast artificial chromosome vector. | two yeast artificial chromosomes containing the entire human nerve growth factor gene were isolated and mapped. by homologous recombination a luciferase gene was precisely engineered into the coding portion of the ngf gene and a neomycin selection marker was placed adjacent to one of the yac telomeres. expression of the yac-based ngf reporter gene and a plasmid-based ngf reporter gene were compared with the regulation of endogenous mouse ngf protein in mouse l929 fibroblasts. in contrast to the ... | 1998 | 9512559 |
| use of mouse mammary tumour virus (mmtv)/neu transgenic mice to identify genes collaborating with the c-erbb-2 oncogene in mammary tumour development. | mouse mammary tumour virus (mmtv)/neu transgenic mice develop clonal or oligoclonal mammary tumours stochastically. the pathology of these tumours is very similar to that of human breast tumours. moreover, these mouse tumours metastasize in the lungs. we present evidence that this mouse model of human breast tumours can be instrumental in identifying novel genes of two distinct classes (activated oncogenes or tumour suppressor genes) which may collaborate with the c-erbb-2/neu transgenic oncogen ... | 1998 | 9513720 |
| induction of a variety of preneoplasias and tumours in the mammary glands of transgenic rats. | although transgenic mouse models for breast cancer have frequently been reported in the literature, transgenic rat models have not been described. we have generated transgenic rats overexpressing the human transforming growth factor alpha (tgf alpha) and c-erbb-2 genes in the mammary gland under the control of the mouse mammary tumour virus (mmtv) long terminal repeat promoter, and have analysed multiple lines of these rats to the second (f2) generation. female mmtv/tgf alpha rats frequently dev ... | 1998 | 9513721 |
| somatic mutations that contribute to breast cancer. | cytogenetic and molecular analyses of primary sporadic human breast carcinomas have documented at least 12 different chromosome arms affected by loss of heterozygosity (loh). this has been taken as evidence for the presence of putative tumour suppressor genes in the remaining allele within the affected regions. we have previously identified three regions on chromosome 17q that are affected by loh in primary human breast tumours. a physical map of one of these regions (17q21) has been prepared. t ... | 1998 | 9513725 |
| nucleolar localization of mouse mammary tumor virus proteins in t-cell lymphomas. | to characterize novel proteins expressed in lymphoma cells, monoclonal antibodies (mabs) were raised against variant s49 mouse lymphoma cells. immunoperoxidase analysis with a specific mab, named m-66, revealed nuclear localization with prominent staining in the nucleoli of both tumorigenic (t-63) cells and nontumorigenic, immunogenic (t-25-adh) cells. weak signals were also observed in the cytoplasm and plasma membrane of both cells. western blot analysis with m-66 antibody revealed a 14-kda pr ... | 1998 | 9514962 |
| identification of glucocorticoid receptor domains necessary for transcriptional activation of the mouse mammary tumor virus promoter integrated in the genome. | it has previously been determined that the mouse mammary tumor virus (mmtv) promoter when integrated in the genome assumes a defined chromatin structure which is disrupted upon addition of glucocorticoids. in contrast, a transiently introduced mmtv promoter has a random nucleoprotein structure. to reveal glucocorticoid receptor (gr) domains necessary for transcriptional activation of the mmtv promoter we compared the effects of mutations of the gr on transcriptional activation of the stably inte ... | 1998 | 9521864 |
| immune response to mouse mammary tumor virus in mice lacking the alpha/beta interferon or the gamma interferon receptor. | mouse mammary tumor virus (mmtv) is a retrovirus which induces a strong immune response and a dramatic increase in the number of infected cells through the expression of a superantigen (sag). many cytokines are likely to be involved in the interaction between mmtv and the immune system. in particular, alpha/beta interferon (ifn-alpha/beta) and gamma interferon (ifn-gamma) exert many antiviral and immunomodulatory activities and play a critical role in other viral infections. in this study, we ha ... | 1998 | 9525580 |
| a novel membrane protein is a mouse mammary tumor virus receptor. | mouse mammary tumor virus (mmtv) infects a number of different cell types, including mammary gland and lymphoid cells, in vivo. to identify the cellular receptor for this virus, a mouse cdna expression library was transfected into cos-7 monkey kidney cells, and those transfected cells able to bind virus were selected by using antibody against the virus's cell surface envelope protein, gp52. one clone isolated from a library prepared from newborn thymus rna, called mtvr, was able to confer virus ... | 1998 | 9525630 |
| genetic recombination as a reporter for screening steroid receptor agonists and antagonists. | reporter cell lines are often used for high throughput screening of chemical libraries to identify new receptor ligands. here we show how cre recombinase can be used in mammalian cells to screen for steroid receptor ligands. a translational fusion of cre recombinase and the ligand binding domain of the human glucocorticoid receptor was transfected into mammalian cells with a loxp/luciferase reporter gene. the recombinase function of the fusion is dependent on ligand binding to the receptor, and ... | 1998 | 9527854 |
| [coevolutive mechanisms between retroviruses and their hosts. the murine mammary tumor model]. | mouse mammary tumor virus (mmtv) is a type b retrovirus that is transmitted as an infectious milk-borne particle and that causes mammary carcinomas by insertional activation of cellular protooncogenes. germ line infections result in endogenous mtv proviruses integrated in the genome of most mouse strains. these endogenous proviruses have been integrated into the genomes of mice for only the past 3-5 million years. the open reading frame present in the 3' long terminal repeat (ltr) of the proviru ... | 1997 | 9532836 |
| the switch in the helical handedness of the histone (h3-h4)2 tetramer within a nucleoprotein particle requires a reorientation of the h3-h3 interface. | it has recently been proposed that the histone (h3-h4)2 tetramer undergoes structural changes, which allow the particle to accommodate both negatively and positively constrained dna. to investigate this process, we modified histone h3 at the h3-h3 interface, within the histone (h2a-h2b-h3-h4)2 octamer or the histone (h3-h4)2 tetramer, by forming adducts on the single cysteine of duck histone h3. we used three sulfhydryl reagents, iodoacetamide, n-ethylmaleimide, and 5,5'-dithiobis(2-nitrobenzoic ... | 1998 | 9535919 |
| efficient presentation of endogenous superantigen by h-2aq. | endogenous superantigens encoded by mouse mammary tumor viruses associate with mhc class ii and interact with t cells bearing particular v beta gene segments. h-2e is more efficient at presentation than h-2a, indeed aq has not been shown to be capable of presenting endogenous superantigens. atypically, the superantigen vsag-3 encoded by mtv-3 is presented efficiently in non-obese diabetic (h-2g7) mice by h-2a; we have examined the independent contributions of vsag-3 and ag7 to this process. ag7 ... | 1998 | 9541599 |
| relative importance of cd4+ and cd8+ t cell repertoires in the development of acute graft-versus-host disease in a murine model of bone marrow transplantation. | t cell repertoire alterations occurring after allogeneic bmt and related emergence of agvhd has not been directly demonstrated. cd4, cd8 and vbeta usage of t cells infiltrating spleen, lymph nodes and liver was compared in lethally irradiated f1(dba/2 x b10.d2) recipients which develop (gvhd mice) or not (long survivor:ls mice) agvhd across minor histocompatibility antigens (mhags) and mtv-6 and mtv-7 encoded super-antigens (sags) barriers according to experimental conditions. the early expansio ... | 1998 | 9543062 |
| dominant-negative interference of the transforming growth factor beta type ii receptor in mammary gland epithelium results in alveolar hyperplasia and differentiation in virgin mice. | transforming growth factor (tgf)-beta1 and tgf-beta3 are normally expressed at high levels in the mammary gland during quiescence and at all stages of development, except lactation. exogenously added tgf-beta1, -beta2, and -beta3 have been shown to regulate growth and differentiation of mammary epithelial cells in vitro and in vivo. tgf-betas signal through a heteromeric complex of type i and type ii serine/threonine kinases. the type ii receptor is necessary for ligand binding and growth suppre ... | 1998 | 9543389 |
| perturbation of beta1-integrin function alters the development of murine mammary gland. | the expression of a transgene coding for a chimeric molecule, containing the cytoplasmic and transmembrane domains of the beta1-integrin chain and the extracellular domain of the t-cell differentiation antigen cd4, was targeted to the mouse mammary gland by the mouse mammary tumor virus (mmtv) promoter. the chimera does not interact with the extracellular ligands; however, its expression in cultured cells was shown to interfere with focal adhesion kinase (fak) phosphorylation following ligation ... | 1998 | 9545227 |
| t helper 1 (th1) and th2 characteristics start to develop during t cell priming and are associated with an immediate ability to induce immunoglobulin class switching. | the respective production of specific immunoglobulin (ig)g2a or igg1 within 5 d of primary immunization with swiss type mouse mammary tumor virus [mmtv(sw)] or haptenated protein provides a model for the development of t helper 1 (th1) and th2 responses. the antibody-producing cells arise from cognate t cell b cell interaction, revealed by the respective induction of cgamma2a and cgamma1 switch transcript production, on the third day after immunization. t cell proliferation and upregulation of m ... | 1998 | 9547331 |
| an entire functional mammary gland may comprise the progeny from a single cell. | any epithelial portion of a normal mouse mammary gland can reproduce an entire functional gland when transplanted into an epithelium-free mammary fat pad. mouse mammary hyperplasias and tumors are clonal dominant populations and probably represent the progeny of a single transformed cell. our study provides evidence that single multipotent stem cells positioned throughout the mature fully developed mammary gland have the capacity to produce sufficient differentiated progeny to recapitulate an en ... | 1998 | 9550724 |
| antisense c-myc retroviral vector suppresses established human prostate cancer. | prostate cancer eventually becomes androgen resistant, resumes growth, and kills the patient. characterization of genetic events that lead to androgen refractory prostatic neoplasia has revealed the frequent overexpression of c-myc and uncontrolled prostate cancer proliferation. a novel strategy to combat advanced prostate cancer utilized a replication incompetent retrovirus that contained the mouse mammary tumor virus (mmtv) promoter within the retroviral vector to allow transcription of antise ... | 1998 | 9551622 |
| enlargement of the ampullary gland and seminal vesicle, but not the prostate in int-2/fgf-3 transgenic mice. | expression of the int2/fgf-3 gene occurs during normal embryonic development and is associated with mammary cancer in mice. overexpression of this gene under the control of the mouse mammary tumor virus long terminal repeat (mmtv-ltr) in males was reported to result in prostatic enlargement. in this report male fgf-3-overexpressing mice were shown to have enlarged ampullary glands, seminal vesicles, and ductus deferens; there was extensive epithelial hyperplasia in the ampullary glands and semin ... | 1998 | 9566308 |
| inhibition of androgen action by dehydroepiandrosterone sulfotransferase transfected in pc-3 prostate cancer cells. | age-dependent loss of androgen sensitivity of the rat liver is associated with a marked increase in dehydroepiandrosterone/hydroxysteroid sulfotransferase (rstd) activity. sulfonated steroid hormones are known to be ineffective in binding receptor proteins. these observations suggest that intracellular androgen sulfonation can physiologically influence androgen action. we have examined the inhibitory effect of rstd on androgen action in the human prostate cancer-derived pc-3 cells transfected wi ... | 1998 | 9566751 |
| [superantigens and murine mammary tumor retrovirus]. | hosts and their pathogens have co-evolved for millions of years, developing multiple and intimate interactions. vertebrates have evolved a very complex immune system which pathogens have often been able to circumvent, in some cases even managing to appropriate some of its components for their own purpose. among the pathogens which do use components of the immune system to survive and propagate, those coding for the expression of superantigens (sags) are now under intense scrutiny. investigations ... | 1997 | 9567341 |
| mouse mammary tumor virus (mmtv), a retrovirus that exploits the immune system. genetics of susceptibility to mmtv infection. | all animals, including humans, show differential susceptibility to infection with viruses. study of the genetics of susceptibility or resistance to specific pathogens is most easily studied in inbred mice. we have been using mouse mammary tumor virus (mmtv), a retrovirus that causes mammary tumors in mice, to study virus/host interactions. these studies have focused on understanding the mechanisms that determine genetic susceptibility to mmtv-induced mammary tumors, the regulation of virus gene ... | 1997 | 9567342 |
| retrovirus-host interactions. the mouse mammary tumor virus model. | mouse mammary tumor virus (mmtv) is a retrovirus which can induce mammary carcinomas in mice late in life by activation of proto-oncogenes after integration in their vicinity. surprisingly, it requires a functional immune system to achieve efficient infection of the mammary gland. this requirement became clear when it was discovered that it has developed strategies to exploit the immune response. instead of escaping immune detection, it induces a vigorous polyclonal t-b interaction which is requ ... | 1997 | 9567343 |
| [searching for retroviral sequences related to human breast cancer]. | the participation of viruses in mammary carcinogenesis has been largely studied in animals. a model similar to the mouse mammary tumor virus (mmtv) was previously proposed. several lines of research supported the participation of mmtv in human breast cancer, but these evidences were contradicted when further research was performed. one major issue was the presence of human endogenous retroviral sequences that confounded results reporting mmtv-like sequences in human breast cancer. to overcome th ... | 1997 | 9567345 |
| transposon-mediated random insertions and site-directed mutagenesis prevent the trafficking of a mouse mammary tumor virus superantigen. | mouse mammary tumor viruses (mmtvs) encode superantigens (sags) which are critical to the life cycle of infectious virus and can mediate extensive deletion of t lymphocytes when expressed by endogenous proviruses. little is known about the structure, intracellular trafficking, or nature of sag association with major histocompatibility (mhc) class ii products. in order to gain a better understanding of sag structure-function relationships, we extensively mutagenized this type ii glycoprotein usin ... | 1998 | 9568034 |
| modulation of hormone-dependent glucocorticoid receptor function using a tetracycline-regulated expression system. | the glucocorticoid receptor (gr) is a ligand-dependent transcription factor capable of stimulating and inhibiting the expression of target genes. to better understand the biological action of glucocorticoids and the function of gr, we have utilized the tetracycline (tc)-regulated mammalian expression system to develop a novel cell line, e8.2/gr3, derived from gr null mouse l929 fibroblasts, that exhibits conditional expression of rat gr. the intracellular concentration of rgr in e8.2/gr3 cells-- ... | 1998 | 9569005 |
| role of the immune response induced by superantigens in the pathogenesis of microbial infections. | superantigens (sags) are microbial proteins which have potent effects on the immune system. they are presented by major histocompatibility complex (mhc) class ii molecules and interact with a large number of t cells expressing specific t cell receptor v beta domains. encounter of a sag leads initially to the stimulation and subsequently to the clonal deletion of reactive t cells. sags are expressed by a wide variety of microorganisms which use them to exploit the immune system to their own advan ... | 1997 | 9571692 |
| mutational and functional analysis of the c-terminal region of the c3h mouse mammary tumor virus superantigen. | the mouse mammary tumor virus (mmtv) encodes within the u3 region of the long terminal repeat (ltr) a protein known as the superantigen (sag). sag is needed for the efficient transmission of milk-borne virus from the gut to target tissue in the mammary gland. mmtv-infected b cells in the gut express sag as a type ii transmembrane protein that is recognized by the variable region of particular beta chains (vbeta) of the t-cell receptor (tcr) on the surface of t cells. recognition of sag by partic ... | 1998 | 9573239 |
| identification and characterization of a tannic acid-responsive negative regulatory element in the mouse mammary tumor virus promoter. | tannic acid, which comprises polyphenolic compounds from tea leaves, suppresses the glucocorticoid-induced gene expression of mouse mammary tumor virus (mmtv) integrated into 34i cells. to investigate whether this suppression is due to promoter responsiveness to tannic acid, we performed chloramphenicol acetyltransferase analysis transfecting a mmtv promoter containing a chloramphenicol acetyltransferase expression vector into mouse fibroblast l929 cells. deletion analysis of the promoter region ... | 1998 | 9575208 |
| recruitment of octamer transcription factors to dna by glucocorticoid receptor. | glucocorticoid receptor (gr) and octamer transcription factors 1 and 2 (oct-1/2) interact synergistically to activate the transcription of mouse mammary tumor virus and many cellular genes. synergism correlates with cooperative dna binding of the two factors in vitro. to examine the molecular basis for these cooperative interactions, we have studied the consequences of protein-protein binding between gr and oct-1/2. we have determined that gr binds in solution to the octamer factor pou domain. b ... | 1998 | 9584182 |
| the position and length of the steroid-dependent hypersensitive region in the mouse mammary tumor virus long terminal repeat are invariant despite multiple nucleosome b frames. | stimulation of the mouse mammary tumor virus with steroids results in the generation of a dnase i-hypersensitive region (hsr) spanning the hormone responsive element (hre) in the long terminal repeat. restriction enzymes were used to characterize the accessibility of various sites within the hsr of mouse mammary tumor virus long terminal repeat-reporter constructions in four different cell lines. the glucocorticoid-dependent hsr was found to span minimally 187 bases, a stretch of dna longer than ... | 1998 | 9584204 |
| chromatin remodelling by the glucocorticoid receptor requires the brg1 complex. | the assembly of transcriptional regulatory dna sequences into chromatin plays a fundamental role in modulating gene expression. the promoter of the mouse mammary-tumour virus (mmtv) is packaged into a regular array of nucleosomes when it becomes stably integrated into mammalian chromosomes, and has been used to investigate the relationship between chromatin architecture and transcriptional activation by the hormone-bound glucocorticoid and progesterone receptors. in mammalian cells that express ... | 1998 | 9590696 |
| characterization of fatty acid synthase in cell lines derived from experimental mammary tumors. | the lipogenic enzyme fatty acid synthase (fas) is elevated in various human primary cancers and certain human cancer cell lines. fas overexpression in human neoplasia has clinical relevance because of its association with tumor aggression and potential chemotherapeutic intervention. here, we surveyed fas in cell lines established from normal murine mammary epithelium (nmumg) and from mammary tumors induced by either rodent polyoma (py) virus or murine mammary tumor virus (mmtv). western blotting ... | 1998 | 9593836 |
| viral superantigen-induced negative selection of tcr transgenic cd4+ cd8+ thymocytes depends on activation, but not proliferation. | t-cell negative selection, a process by which intrathymic immunological tolerance is induced, involves the apoptosis-mediated clonal deletion of potentially autoreactive t cells. although different experimental approaches suggest that this process is triggered as the result of activation-mediated cell death, the signal transduction pathways underlying this process is not fully understood. in the present report we have used an in vitro system to analyze the cell activation and proliferation requi ... | 1998 | 9596673 |
| polyamines induce malignant transformation in cultured nih 3t3 fibroblasts. | previous studies have demonstrated that polyamines accumulate in cancer cells and that overproduction of ornithine decarboxylase (odc), which catalyzes polyamine synthesis, elicits the acquisition of the transformed phenotype. however, it was not clear whether the overexpression of odc and the accumulation of polyamines are only innocent by-products of the transformation process. in this study we demonstrate that polyamines as such, may play a crucial role in malignant transformation. the system ... | 1998 | 9597759 |
| human progesterone receptor a and b isoforms in cho cells. ii. comparison of binding, transactivation and ed50 values of several synthetic (anti)progestagens in vitro in cho and mcf-7 cells and in vivo in rabbits and rats. | the human progesterone receptor a and b isoforms (hpr-a and hpr-b) were stably transfected in chinese hamster ovary (cho) cells in the presence or absence of the mouse mamma tumor virus (mmtv) promoter and luciferase (luc) reporter gene. in this way four stably transfected cho cell lines, i.e. hpr-a, hpr-b, hpr-a-mmtv-luc and hpr-b-mmtv-luc cells, were prepared. hpr-a and -b isoforms were compared by binding and transactivation analysis for 14 progestagens and 7 antiprogestagens. thereby org 205 ... | 1998 | 9605410 |
| functional activities of the a and b forms of the human androgen receptor in response to androgen receptor agonists and antagonists. | the androgen receptor (ar) is present in many cells in two forms. the b form migrates with an apparent mass of 110 kda and constitutes more than 80% of the immunoreactive receptor in most cell types. the a form of the ar migrates with an apparent mass of 87 kda, appears to derive from internal translation initiation at methionine-188 in the ar open-reading frame, and usually constitutes 20% or less of the immunoreactive ar present. previous experiments designed to examine the functional capacity ... | 1998 | 9605928 |
| auxiliary downstream elements are required for efficient polyadenylation of mammalian pre-mrnas. | we have previously identified a g-rich sequence (grs) as an auxiliary downstream element (aux dse) which influences the processing efficiency of the sv40 late polyadenylation signal. we have now determined that sequences downstream of the core u-rich element (ure) form a fundamental part of mammalian polyadenylation signals. these novel aux dses all influenced the efficiency of 3'-end processing in vitro by stabilizing the assembly of cstf on the core downstream ure. three possible mechanisms by ... | 1998 | 9611233 |
| negative regulation of the rat glutathione s-transferase a2 gene by glucocorticoids involves a canonical glucocorticoid consensus sequence. | glucocorticoids (gcs) repress both basal and polyaromatic hydrocarbon-induced expression of the glutathione s-transferase ya1 gene (gsta2) in isolated rat hepatocytes and rat liver in vivo. transient transfection experiments with hepg2 cells were used to identify gc-responsive elements (gres). with cotransfected gc receptor, chloramphenicol acetyltransferase (cat) constructs containing a palindromic gre (pgre) and three gre hexanucleotide half-sites between -1.6 and -1.1 kb of the 5'-flanking re ... | 1998 | 9614203 |
| in vitro and in vivo antisense-mediated growth inhibition of a mammary adenocarcinoma from mmtv-neu transgenic mice. | oncogene-bearing transgenic mice develop various kinds of tumors depending on both the regulatory sequences and the specific oncogene used. these mice not only help to clarify the pathogenetic pathways leading to tumor formation, but can also be useful as models to test novel therapeutic strategies, including gene therapy. we have previously reported the establishment of an mmtv-neu (erbb-2) transgenic mouse lineage, in which 100% of females develop breast tumors with many features similar to th ... | 1998 | 9614559 |
| the mouse mammary tumour virus promoter positioned on a tetramer of histones h3 and h4 binds nuclear factor 1 and otf1. | modulation of eukaryotic gene expression is influenced by the organization of regulatory dna-elements in chromatin. the mouse mammary tumor virus (mmtv) promoter exhibits regularly positioned nucleosomes that reduce the accessibility of the binding sites for sequence-specific transcription factors, in particular nuclear factor (nf1). hormonal induction of the mmtv promoter is accompanied by remodeling of the nucleosomal structure, but the biochemical nature of these structural changes is unknown ... | 1998 | 9614938 |
| regulatory cd4 t cells: expression of il-2r alpha chain, resistance to clonal deletion and il-2 dependency. | we recently characterized a cd4+ t cell population expressing the il-2r alpha chain (cd25), producing il-10 and resisting clonal deletion induced by viral superantigen (vsag) encoded by mouse mammary tumor virus [mmtv(sw)]. we now report that these apoptosis-resistant cells are generated in the thymus but not from the immature cd4+ cd8+ thymocytes. they migrate from the thymus and are found in the periphery from at least the 10th day of life, after which they expand with the same kinetics in nor ... | 1998 | 9620592 |
| mouse mammary tumor virus superantigen expression in b cells is regulated by a central enhancer within the pol gene. | expression of mouse mammary tumor virus (mmtv)-encoded superantigens in b lymphocytes is required for viral transmission and pathogenesis. the mechanism of superantigen expression from the viral sag gene in b cells is largely unknown, due to problems with detection and quantification of these low-abundance proteins. we have established a sensitive superantigen-luciferase reporter assay to study the expression and regulation of the mmtv sag gene in b-cell lymphomas. the regulatory elements for re ... | 1998 | 9621071 |
| a dual-luciferase reporter system for studying recoding signals. | a new reporter system has been developed for measuring translation coupling efficiency of recoding mechanisms such as frameshifting or readthrough. a recoding test sequence is cloned in between the renilla and firefly luciferase reporter genes and the two luciferase activities are subsequently measured in the same tube. the normalized ratio of the two activities is proportional to the efficiency with which the ribosome "reads" the recoding signal making the transition from one open reading frame ... | 1998 | 9630253 |
| genetic modulation of neu proto-oncogene-induced mammary tumorigenesis. | modulation of oncogene-induced carcinogenesis by secondary mutation or genetic background may be an important factor in determining the expression of the tumor phenotype. we have investigated the role of loss of function mutations and strain-specific genetic elements in the modulation of oncogene-induced breast cancer using a murine model. fvb female mice transgenic for the rat neu proto-oncogene [mouse mammary tumor virus (mmtv)-neu] developed mammary tumors between 7 and 12 months of age, wher ... | 1998 | 9635596 |
| disregulation of ocular morphogenesis by lens-specific expression of fgf-3/int-2 in transgenic mice. | fgf-3, originally named int-2, was discovered as an oncogene frequently activated in mammary carcinomas resulting from the chromosomal integration of the mouse mammary tumor virus (mmtv). int-2 was later designated fgf-3 based on sequence homology with other members of the fibroblast growth factor (fgf) family. fgf-1 is the prototypical member of the fgf family, and is the only family member which activates all known fgf receptor isoforms. transgenic mice expressing in the lens a form of fgf-1 e ... | 1998 | 9640329 |
| [superantigens and retroviral infections. increase of mammary tumorigenicity due to recombination between exogenous and endogenous mmtv viruses]. | a number of milk-borne exogenous mouse mammary tumor viruses (mmtv) infect mice shortly after birth and, when expressed, produce superantigens. herein we describe the biological effects of new variants of exogenous mmtv: one of them (balb14) present in balb/c mice and showing a low ability to induce mammary tumors, and the other (mmtv-7) being the result of recombination between the balb14 and the mtv-7 endogenous provirus. the recombinant virus which has the sag-specificity of mtv-7 was amplifi ... | 1997 | 9640768 |
| myc/p53 interactions in transgenic mouse mammary development, tumorigenesis and chromosomal instability. | we have examined defects in mammary development and tumorigenesis in a transgenic model expressing the c-myc gene under the mmtv-ltr promoter. the stochastic tumors which arise from hyperplastic ductal and lobular lesions in this model are characterized by high rates both of apoptosis and of chromosomal instability. since the p53 gene product is thought to be central in the maintenance of genomic integrity, in part due to its ability to induce apoptosis in cells harboring dna damage, we examined ... | 1998 | 9652742 |
| a role for herpesvirus saimiri orf14 in transformation and persistent infection. | the product of open reading frame 14 (orf14) of herpesvirus saimiri (hvs) exhibits significant homology with mouse mammary tumor virus superantigen. orf14 encodes a 50-kda secreted glycoprotein, as shown previously (z. yao, e. maraskovsky, m. k. spriggs, j. i. cohen, r. j. armitage, and m. r. alderson, j. immunol. 156:3260-3266, 1996). orf14 expressed from recombinant baculovirus powerfully induces proliferation of cd4-positive cells originating from several different species. to study the role ... | 1998 | 9658125 |
| calcium/calmodulin kinase inhibitors and immunosuppressant macrolides rapamycin and fk506 inhibit progestin- and glucocorticosteroid receptor-mediated transcription in human breast cancer t47d cells. | the effects of immunosuppressants and inhibitors of specific calcium/calmodulin kinase (camk) of types ii and iv on progestin/glucocorticosteroid-induced transcription were studied in two human stably transfected breast cancer t47d cell lines. the lines contain the chloramphenicol acetyl transferase (cat) gene under control either of the mouse mammary tumor virus promoter (t47d-mmtv-cat), or the minimal promoter containing five glucocorticosteroid/progestin hormone response elements [t47d-(gre)5 ... | 1998 | 9658403 |
| nuclear factor i (nfi) isoforms differentially activate simple versus complex nfi-responsive promoters. | promoter-specific differences in the function of transcription factors play a central role in the regulation of gene expression. we have measured the maximal transcriptional activation potentials of nuclear factor i (nfi) proteins encoded by each of the four identified nfi genes (nfi-a, -b, -c, and -x) by transient transfection in jeg-3 cells using two model nfi-dependent promoters: 1) a simple chimeric promoter containing a single nfi-binding site upstream of the adenovirus major late promoter ... | 1998 | 9660824 |
| permanent alteration of endogenous gangliosides in neuroblastoma cells by stable transfection with antisense vector. | | 1998 | 9668392 |
| loss of endogenous mouse mammary tumor virus superantigen increases tumor resistance. | from a cross between a tumor-susceptible mouse strain (dba/2; d) and a tumor-resistant mhc-identical strain (b10.d2; d2) new recombinant inbred mouse strains were established over many generations of inbreeding and tumor resistance selection. since resistance to the highly metastatic dba/2 lymphoma variant esb had an immunologic basis, and the two parental strains differed in endogenous viral superantigens (vsags), dna of three d2 x d recombinant inbred mouse lines was typed for endogenous mouse ... | 1998 | 9670928 |
| reduced metastasis of polyoma virus middle t antigen-induced mammary cancer in plasminogen-deficient mice. | to investigate the role of plasmin(ogen) in mammary tumor development and progression, plasminogen-deficient mice were crossed with transgenic mice expressing polyoma middle t antigen under the control of the mouse mammary tumor virus long terminal repeat. virgin females carrying the polyoma middle t antigen uniformly developed multiple, bilateral mammary tumors, regardless of the presence or absence of circulating plasminogen. both the age at which these tumors became palpable and subsequent tu ... | 1998 | 9671388 |
| agonist-specific modulation of glucocorticoid receptor-mediated transcription by immunosuppressants. | although the immunosuppressive drugs fk506, rapamycin and cyclosporin a have been reported to potentiate transcriptional activation mediated by a non-saturating concentration of the glucocorticoid receptor agonist dexamethasone, the precise mechanism(s) underlying these responses remains unclear. the murine l-929-derived lmcat cell line stably transfected with the mouse mammary tumor virus promoter-chloramphenicol acetyl transferase reporter gene construct was utilized in the present study to fu ... | 1998 | 9685211 |
| assembly of mmtv promoter minichromosomes with positioned nucleosomes precludes nf1 access but not restriction enzyme cleavage. | to generate long arrays of nucleosomes within a topologically defined chromatin domain we have assembled minichromosomes on negatively supercoiled plasmid dna with extracts from drosophila preblastoderm embryos. these minichromosomes are dynamic substrates for energy-dependent nucleosome remodeling machines that facilitate the binding of various transcription factors but do not exhibit nucleosome positioning. in contrast, if such minichromosomes include the mouse mammary tumour virus (mmtv) prom ... | 1998 | 9685480 |
| sequence-specific binding of ku autoantigen to single-stranded dna. | glucocorticoid-induced transcription of mouse mammary tumor virus is repressed by ku antigen/dna-dependent protein kinase (dna-pk) through a dna sequence element (nre1) in the viral long terminal repeat. nuclear factors binding to the separated single strands of nre1 have been identified that may also be important for transcriptional regulation through this element. we report the separation of the upper-stranded nre1 binding activity in jurkat t cell nuclear extracts into two components. one com ... | 1998 | 9694826 |
| mapping of a mouse mammary tumor virus integration site by retroviral ltr--arbitrary polymerase chain reaction. | the de novo integration of retroviral genomes within the mammalian genome is believed to contribute to the tumorigenic process. integration may result in the disruption or inappropriate transcription of key regulatory genes. we describe the application of an arbitrarily primed pcr method for the mapping and cloning of genomic integration sites of the mouse mammary tumor virus (mmtv). we have amplified dna sequences between a selected retroviral mmtv-ltr and random sites in the 3' flanking dna. u ... | 1998 | 9696128 |