| preactivation of b lymphocytes does not enhance mouse mammary tumor virus infection. | we investigated whether mouse mammary tumor virus (mmtv) favors preactivated or naive b cells as targets for efficient infection. we have demonstrated previously that mmtv activates b cells upon infection. here, we show that polyclonal activation of b cells leads instead to lower infection levels and attenuated superantigen-specific t-cell responses in vivo. this indicates that naive small resting b cells are the major targets of mmtv infection and that the activation induced by mmtv is sufficie ... | 1998 | 9696877 |
| atp-mediated activation of rna polymerase ii transcription complexes. | transcription initiation by rna polymerase ii is a complex, multistep process that minimally involves transcription complex assembly, open complex formation, and promoter clearance. hydrolysis of the beta--gamma phosphoanhydride bond of atp has previously been shown to be required for open complex formation, as well as for the phosphorylation of the carboxy-terminal domain of the largest subunit of rna polymerase ii. the observation that atp-dependent activation of transcription complexes can be ... | 1998 | 9699480 |
| intranuclear trafficking and gene targeting by members of the steroid/nuclear receptor superfamily. | upon binding to regulatory elements in mammalian chromosomes, steroid receptors induce specific transitions in the nucleoprotein structure of the template. these transitions reflect, in part, the reorganization of chromatin structure to permit interaction of secondary factors with target sequences in promoter regulatory regions. steroid receptors represent a class of transcriptional activators that are able to interact with repressed nucleoprotein templates and recruit necessary activities for c ... | 1998 | 9699865 |
| dexamethasone and triamcinolone acetonide accumulation in mouse fibroblasts is differently modulated by the immunosuppressants cyclosporin a, fk506, rapamycin and their analogues, as well as by other p-glycoprotein ligands. | in mouse fibroblasts (lmcat cells) stably transfected with the reporter gene chloramphenicol acetyl transferase under the control of the mouse mammary tumor virus promoter (mmtv-cat), cyclosporin a (csa), fk506, and rapamycin (rap) at micromolar concentrations potentiate dexamethasone- (dex) induced cat gene activity in a dose-dependent way (renoir j.-m., mercier-bodard c., hoffmann k., le bihan s., ning y. m., sanchez e. r., handschumacher r. e. and baulieu e. e., proc. natl. acad. sci. u.s.a., ... | 1998 | 9712407 |
| functional interactions of the af-2 activation domain core region of the human androgen receptor with the amino-terminal domain and with the transcriptional coactivator tif2 (transcriptional intermediary factor2). | previous studies in yeast and mammalian cells showed a functional interaction between the amino-terminal domain and the carboxy-terminal, ligand-binding domain (lbd) of the human androgen receptor (ar). in the present study, the ar subdomains involved in this in vivo interaction were determined in more detail. cotransfection experiments in chinese hamster ovary (cho) cells and two-hybrid experiments in yeast revealed that two regions in the nh2-terminal domain are involved in the functional inte ... | 1998 | 9717843 |
| [requirement of class ii and membrane proximal region of mouse mammary tumor virus superantigen (mtv sag) in mtv7 sag presentation]. | although in some cases superantigens (sags) have been shown to bind directly to t cell receptor (tcr) in the absence of mhc molecules, the precise role of mhc class ii in sag presentation to t cells is not thoroughly understood. in particular, it is still not known whether mhc class ii is a mere transporter of mouse mammary tumor virus (mtv) sag to the cell surface or an essential component complexed with sags for tcr triggering. in this study, we found that mhc class ii negative b cell line tra ... | 1998 | 9719947 |
| resistance of human leukemic cem-c1 cells is overcome by synergism between glucocorticoid and protein kinase a pathways: correlation with c-myc suppression. | glucocorticoids (gcs) induce apoptosis in lymphoid cells that contain functional gc receptors (grs). however, gc resistance often is seen in cells with demonstrable grs; one such line is cem-c1. we have tested the hypothesis that positive interactions between gc and cyclic amp (camp) regulate gc actions in cem clones. treatment of both gc-resistant cem-c1 [resistant to 1 microm dexamethasone (dex)] and the sensitive sister clone, cem-c7 (approximately 65% cell death with 20 nm dex, approximately ... | 1998 | 9721879 |
| modulation of disease by superantigens. | increasing evidence suggests that bacterial and viral superantigens are involved in immune-mediated disease. studies using an animal model for multiple sclerosis show that superantigens can induce relapses and bring into play autoreactive t cells with restricted usage of t cell receptor v beta families that may be indirectly involved in the initial episode of disease. this may also involve epitope spreading. superantigens have also been implicated in other autoimmune diseases such as rheumatoid ... | 1998 | 9722924 |
| mutation of aspartate-233 to valine in mouse ornithine decarboxylase reduces enzyme activity. | ornithine decarboxylase is the first and key enzyme in mammalian polyamine biosynthesis. all eukaryotic ornithine decarboxylases contain several highly conserved regions and the amino acid residues 232-238 form one of the most highly conserved sequences. this region contains a glycine-rich sequence typically found in a number of pyridoxal 5'-phosphate-dependent or nucleotide-binding proteins. we mutated aspartate-233 which is the only acidic residue within this region to valine. this mutation ca ... | 1998 | 9722985 |
| b and t cells are required for mouse mammary tumor virus spread within the mammary gland. | mouse mammary tumor virus (mmtv) is an infectious retrovirus transmitted through milk from mother to newborns. mmtv encodes a superantigen (sag) whose activity is indispensable for the virus life cycle, since a genetically engineered virus with a mutation in the sag gene neither amplified in cells of the immune system of suckling pups nor infected their mammary glands. when wild-type mmtv was injected directly into the mammary glands of uninfected pubescent mice, their lymphoid as well as mammar ... | 1998 | 9725233 |
| mechanism of hiv pathogenesis: role of superantigens in disease. | initial infection with human immunodeficiency virus (hiv) results in a burst of viremia and an ensuing spread of virus to secondary lymphoid organs, after which a "latency" period occurs with little or no virus detectable in the circulation. the term latent period has been shown to be a misnomer, because substantial viral replication occurs during this time in lymph nodes, although clinically there appears to be few symptoms of disease. however, a telling indicator of active infection during thi ... | 1998 | 9727632 |
| induction of endogenous mammary tumor virus in lymphocytes infected with murine acquired immunodeficiency syndrome virus. | mice infected with murine acquired immunodeficiency syndrome (maids) virus developed lymphoadenopathy and profound immunodeficiency. concomitantly the expression of endogenous mammary tumor virus (mtv) mrna increased significantly, especially for the 1.7-kb 3' open reading frame (orf) mrna encoding mtv superantigen. b cell lines that are established from maids mice and exhibit superantigen activity also express a high level of 1.7-kb endogenous mtv and mrna. infection of a b cell tumor line in v ... | 1998 | 9732700 |
| the secondary structure of the r region of a murine leukemia virus is important for stimulation of long terminal repeat-driven gene expression. | in addition to their role in reverse transcription, the r-region sequences of some retroviruses affect viral transcription. the first 28 nucleotides of the r region within the long terminal repeat (ltr) of the murine type c retrovirus sl3 were predicted to form a stem-loop structure. we tested whether this structure affected the transcriptional activity of the viral ltr. mutations that altered either side of the stem and thus disrupted base pairing were generated. these decreased the level of ex ... | 1998 | 9733816 |
| purification and characterization of a cellular protein that binds to the downstream activation sequence of the strict late ul38 promoter of herpes simplex virus type 1. | previous work on the strict late (gamma) ul38 promoter of herpes simplex virus type 1 identified three cis-acting elements required for wild-type levels of transcription: a tata box at -31, a consensus mammalian initiator element at the transcription start site, and a downstream activation sequence (das) at +20 to +33. das is found in similar locations on several other late promoters, suggesting an important regulatory role in late gene expression. in this communication, we further characterize ... | 1998 | 9733860 |
| expression of ovine insulin-like growth factor-1 (igf-1) stimulates alveolar bud development in mammary glands of transgenic mice. | to determine whether murine mammary growth is modulated by local insulin-like growth factor-1 (igf-1) production, expression of recombinant igf-1 was directed to the mammary glands of transgenic mice using an ovine prepro igf-1 cdna under control of the mouse mammary tumor virus-long terminal repeat (mmtv-ltr) promoter. bioactivity of recombinant igf-1 in transgenic mouse milk extracts was demonstrated by a concentration-dependent increase in [3h]thymidine incorporation in clonal bovine mammary ... | 1998 | 9741830 |
| differential gene induction by glucocorticoid and progesterone receptors. | the question of how glucocorticoid, progesterone, androgen, and mineralocorticoid receptors can generate distinct patterns of gene expression despite similar, if not identical, dna sequence recognition properties is a central question in steroid biology. this study addresses the hypothesis that glucocorticoid and progesterone receptors can differentially utilize the promoter context created by a series of receptor recognition sites. this hypothesis predicts that for different receptors an indivi ... | 1998 | 9744514 |
| ion-rna interactions in the rna pseudoknot of a ribosomal frameshifting site: molecular modeling studies. | the three-dimensional (3-d) structure of a rna pseudoknot that causes the efficient ribosomal frameshifting in the gag-pro region of mouse mammary tumor virus (mmtv) has been determined recently by nuclear magnetic resonance (nmr) studies. but since the structure refinement in the studies did not use metal ions and waters, it is not clear how metal ions participate in the stabilization of the pseudoknot, and what kind of ion-rna interactions dominate in the tertiary contacts for the rna pseudokn ... | 1998 | 9745889 |
| progesterone stimulates the activity of the promoters of peripheral myelin protein-22 and protein zero genes in schwann cells. | to understand better the mechanisms by which progesterone (prog) promotes myelination in the pns, cultured rat schwann cells were transiently transfected with reporter constructs in which luciferase expression was controlled by the promoter region of either the peripheral myelin protein-22 (pmp22) or the protein zero (p0) genes. prog stimulated the p0 promoter and promoter 1, but not promoter 2, of pmp22. the effect of prog was specific, as estradiol and testosterone only weakly activated promot ... | 1998 | 9751213 |
| transduction pathways involved in rapid hormone receptor regulation in the mammary epithelium. | previous studies have shown that the envelope protein of the mouse mammary tumor virus (mmtv) rapidly upregulates prolactin (prl) receptors by shifting them from internal pools to the cell surface and downregulates epidermal growth factor (egf) receptors by inducing their internalization and degradation. this study shows that the effect on prl receptors is mediated by the nitric oxide (no)/cgmp pathway, since it can be mimicked by an no donor or 8-bromo-cgmp and can be blocked by an no synthase ... | 1998 | 9755072 |
| possible retroviral etiology of human breast cancer. | since the discovery in the early 1980s that retroviruses are pathogenic to man, the mouse mammary tumor viruses (mmtvs) received great attention. studies of mmtvs allowed considerable insights into the mechanisms at work in breast tumorigenesis. mmtvs are essentially insertional mutagenes. numerous oncogenes have been found altered by mmtvs, either specific for mmtvs or not. however, despite considerable attempts, the involvement of mmtvs in human breast cancer remains questionable. yet a retrov ... | 1998 | 9755790 |
| p300/creb-binding protein enhances the prolactin-mediated transcriptional induction through direct interaction with the transactivation domain of stat5, but does not participate in the stat5-mediated suppression of the glucocorticoid response. | stat5 was discovered as a prl-induced member of the stat (signal transducer and activator of transcription) family. its induction by many other cytokines and interleukins suggests that stat5 plays a crucial role not only in mammary epithelial, but also in hematopoietic cells. cell type- and promoter-specific functions of stat5 are most likely modulated by the interaction with other transcription factors. we recently showed cross-talk between stat5 and the glucocorticoid receptor. the activated g ... | 1998 | 9773981 |
| active signaling by neu in transgenic mice. | transgenic mice engineered to overexpress the her-2/neu/erbb-2 protooncogene under the control of a mammary-specific promoter develop mammary tumors and are a model for human breast cancer. signal transduction by neu was examined in situ in the tumors of these transgenic mice. this was accomplished using the pn2a monoclonal antibody, which recognizes neu only in the phosphorylated, and therefore actively signaling, state. immunohistochemistry using pn2a demonstrated that neu actively signals in ... | 1998 | 9778054 |
| phorbol ester causes ligand-independent activation of the androgen receptor. | we have examined the human androgen receptor (har) for its ability to activate ar-dependent transcription of a transgene in a ligand-independent manner. the transcriptional activity was determined by analysis of chloramphenicol acetyltransferase (cat) activity in t47d cells cotransfected with a plasmid expressing the har and a natural ar-regulated promoter (the mvdp androgen-dependent enhancer) ligated to the reporter cat gene. in this study, the effects of the protein kinase c (pkc) activator 1 ... | 1998 | 9780230 |
| activation of fgf8 in s115 mouse mammary tumor cells is associated with genomic integration of mouse mammary tumor virus. | fgf8 is an embryonally expressed mitogenic fibroblast growth factor which has transforming capacity. it is expressed in s115 mouse mammary tumor cells (s115 cells) and in parental tumors of dd/sio mice as well as in some human breast and prostate cancer cell lines. in s115 cells androgens induce the expression of fgf8 which seems to be associated with the androgen-maintained malignant phenotype of the cells. s115 cells also contain and express mtv proviruses known to insertionally activate oncog ... | 1998 | 9784427 |
| expression of t:g mismatch-specific thymidine-dna glycosylase and dna methyl transferase genes during development and tumorigenesis. | in situ hybridization was used to characterize the expression pattern of the t:g mismatch-specific thymidine-dna glycosylase (tdg) gene, encoding a dna repair enzyme which corrects g:t mismatches that result from the hydrolytic deamination of 5-methyl cytosines. tdg transcripts were uniformly and ubiquitously expressed from 7.5-13.5 days post-coitum, but were then markedly enriched in specific tissues of the developing fetus. at 14.5 gestational days, tdg was strongly expressed in the developing ... | 1998 | 9794235 |
| expression of mouse mammary tumor virus-like env gene sequences in human breast cancer. | we have reported previously (wang et al, cancer res., 55: 5173-5179, 1995) the presence of a 660-bp sequence that is 90-98% homologous to the env gene of mouse mammary tumor virus in 38% of 314 unselected breast cancer samples, in some breast cancer cell lines, and in 1.8% of the 107 normal breast specimens from reduction mammoplasties. in this communication, we have investigated whether the 660-bp sequence or a smaller 256-bp sequence within the 660 bp were expressed in breast tumors, normal br ... | 1998 | 9796992 |
| regulation of mammary hormone receptor metabolism by a retroviral envelope protein. | in a previous study, the envelope protein (gp52) of the mouse mammary tumour virus (mmtv) was shown to facilitate mammary gland differentiation by increasing prolactin (prl) receptors via increased receptor synthesis and via the redistribution of existing receptors from an internal pool. in this study, receptors for other hormones known to affect mammary gland metabolism were investigated. epidermal growth factor (egf) stimulates mammary epithelial growth and inhibits differentiation; its recept ... | 1998 | 9801459 |
| differential reactivity of tcr vbeta10 alleles to a mouse mammary tumor virus superantigen. | mouse mammary tumor virus (mmtv) expresses a superantigen (sag) which plays a critical role in the viral life cycle. we have recently described the new infectious mmtv (sim) encoding a vbeta4-specific sag in mice with a tcr-vbeta(b) haplotype. we have now compared the sag activity of this virus in balb/c mice harboring the tcr-vbeta(a), tcr-vbeta(b) or tcr-vbeta(c) haplotypes which differ by a central deletion in the tcr-vbeta(a) and tcr-vbeta(c) locus and by mutations in some of the remaining v ... | 1998 | 9808176 |
| mouse mammary tumor virus sequences responsible for activating cellular oncogenes. | integration of mouse mammary tumor virus (mmtv) near the int genes results in the inappropriate expression of these proto-oncogenes and initiates events that lead to the formation of mammary adenocarcinomas. in most cases, the mmtv provirus integrates in a transcriptional orientation opposite that of the int genes. we have used a novel, vector-based system designed to recapitulate the integration of mmtv upstream of the int-2 promoter. compared to a cellular promoter or another retroviral promot ... | 1998 | 9811675 |
| the regional integration of retroviral sequences into the mosaic genomes of mammals. | we have reviewed here three sets of data concerning the integration of retroviral sequences in the mammalian genome: (i) our experimental localization of a number of proviruses integrated in isochores characterized by different gc levels; (ii) results from other laboratories on the localization of retroviral sequences in open chromatin regions and/or next to cpg islands; and (iii) our compositional analysis of genes located in the neighborhood of integrated retroviral sequences. the three sets o ... | 1998 | 9813219 |
| [correlation between expression of antigen immunologically related to gp52 mmtv and transcription of homologous env mmtv dna sequences in peripheral blood lymphocytes from breast cancer patients]. | previously we reported that hmcag related to gp52, env product of mmtv, was a specific marker of human breast cancer (bc). this antigen was expressed not only in bc tissue and patients' sera, but in peripheral t- and b-cells. hmcag was found in 21.4% of healthy donors, but only in the fraction rich in b-cells. we searched for env-homologous sequences in bc patients by northern and southern dot-blot hybridization of plasmid clones containing env mmtv with total rna and dna of peripheral blood lym ... | 1998 | 9819826 |
| induction and inhibition of cd40-cd40 ligand interactions: a new strategy underlying host-virus relationships. | interaction between cd40 and the cd40 ligand (cd40l) is required for mouse mammary tumor virus (mmtv) propagation. we found that fas was expressed on b cells and cd40l on a small subset of viral superantigen-cognate t cells 12 h after mmtv(sw) infection. cd40l and fas were down-regulated after 24 h. all cd4 t cells then became resistant to anti-cd3-induced cd40l induction in vitro for 2 wk. initiation of cd40l expression and its rapid shut-off was associated with il-12 production and was control ... | 1998 | 9820509 |
| in vitro binding of h1 histone subtypes to nucleosomal organized mouse mammary tumor virus long terminal repeat promotor. | the binding of all known linker histones, named h1a through h1e, including h1(0) and h1t, to a model chromatin complex based on a dna fragment containing the mouse mammary tumor virus long terminal repeat promotor was systematically studied. as for the histone subtype h1b, we found a dissociation constant of 8-16 nm to a single mononucleosome (210 base pairs), whereas the binding constant of all other subtypes varied between 2 and 4 nm. most of the h1 histones, namely h1a, h1c, h1d/e, and h1(0), ... | 1998 | 9822702 |
| solution structure and backbone dynamics of mason-pfizer monkey virus (mpmv) nucleocapsid protein. | retroviral nucleocapsid proteins (ncps) are cchc-type zinc finger proteins that mediate virion rna binding activities associated with retrovirus assembly and genomic rna encapsidation. mason-pfizer monkey virus (mpmv), a type d retrovirus, encodes a 96-amino acid nucleocapsid protein, which contains two cys-x2-cys-x4-his-x4-cys (cchc) zinc fingers connected by an unusually long 15-amino acid linker. homonuclear, two-dimensional sensitivity-enhanced 15n-1h, three-dimensional 15n-1h, and triple re ... | 1998 | 9827993 |
| steroid-selective initiation of chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter is controlled by the site of promoter integration. | the mouse mammary tumor virus (mmtv) promoter has target sequences recognized by several steroid receptors. we present evidence for a novel mechanism that confers hormone specificity to this promoter. we show that remodeling of mmtv chromatin and the concomitant activation of the mmtv promoter are induced equally by glucocorticoids and progestins in one chromosomal context but are selective for glucocorticoids in another. furthermore, increased histone acetylation modulates mmtv promoter regulat ... | 1998 | 9830013 |
| antiandrogen action in the development of androgen insensitivity in s115 mouse mammary tumour cells. | endocrine therapy for steroid-sensitive tumours often involves administration of steroid antagonists which are designed to bind to the steroid receptor and block steroid action. however, the clinical problem remains the temporary nature of the tumour regression. since in vitro models suggest that steroid ablation itself can result in loss of steroid sensitivity of tumour cells, these studies aimed to investigate the influence of the antiandrogen ici 141,307 on this progression. this antiandrogen ... | 1993 | 9831478 |
| rna polymerase ii transcription complex assembly in nuclear extracts. | in vitro transcription systems based on nuclear extracts of eukaryotic cells continue to be valuable experimental systems for assessing function of promoter sequences and defining new activities involved in transcription complex assembly and activity, but many aspects of such systems have not been experimentally examined. here, transcription complex assembly on the promoter from the long terminal repeat of mouse mammary tumor virus was assessed in vitro with a transcription system derived from n ... | 1998 | 9840811 |
| mmtv-fgf8 transgenic mice develop mammary and salivary gland neoplasia and ovarian stromal hyperplasia. | prior studies have identified fibroblast growth factor-8 (fgf8) as a possible proto-oncogene in mouse mammary tumorigenesis. we now report on the generation of two types of fgf8 transgenic mice that each utilize the mouse mammary tumor virus (mmtv) promoter. the first transgene (mmtv-fgf8b) results in the overexpression of the fgf8b isoform exclusively. male and female mmtv-fgf8b transgenic mice are viable and fertile. rna for fgf8b is detected in mammary gland and salivary gland tissues of tran ... | 1998 | 9840935 |
| mammary gland expression of mouse mammary tumor virus is regulated by a novel element in the long terminal repeat. | mouse mammary tumor virus (mmtv) infects both lymphoid tissue and lactating mammary gland during its infectious cycle, but some endogenous mmtvs are transcribed only in lymphoid cells. we found a lymphoid cell-specific endogenous mmtv that was converted to a milk-borne, infectious virus through recombination with an exogenously transmitted mmtv. the changed expression pattern correlated with the alteration of a single base pair in the long terminal repeat of the lymphoid cell-specific virus. tra ... | 1999 | 9847341 |
| the matrix metalloproteinase matrilysin influences early-stage mammary tumorigenesis. | overexpression of the epithelial specific matrix metalloproteinase matrilysin (mat) has been correlated with enhanced tumorigenicity and tumor cell invasion using in vitro model systems. we have determined the effects of mat expression on the development of mammary tumorigenesis using transgenic mice that express human mat under the control of the mouse mammary tumor virus (mmtv)-long terminal repeat promoter/enhancer. examination of mammary glands from multiparous mmtv-mat animals revealed the ... | 1998 | 9850086 |
| overexpression of vegf in testis and epididymis causes infertility in transgenic mice: evidence for nonendothelial targets for vegf. | vascular endothelial growth factor (vegf) is a key regulator of endothelial growth and permeability. however, vegf may also target nonendothelial cells, as vegf receptors and responsiveness have been detected for example in monocytes, and high concentrations of vegf have been reported in human semen. in this work we present evidence that overexpression of vegf in the testis and epididymis of transgenic mice under the mouse mammary tumor virus (mmtv) ltr promoter causes infertility. the testes of ... | 1998 | 9852161 |
| telomere length, telomerase activity and telomerase rna expression during mouse mammary tumor progression. | to investigate the roles of telomere length (mean length of the terminal restriction fragments; trfs), telomerase activity (ta) and telomerase rna (mtr) expression in relation to mouse mammary tumor progression, we examined a pregnancy-dependent mouse mammary tumor line (tpdmt-4) and its four autonomous sublines (t4-oi320: non-metastatic; and t4-oi165, -oi96, and -oi145: artificial metastatic) of ddd/1 mouse origin, and an autonomous growing mammary tumor (jyg-mc) showing spontaneous lung metast ... | 1998 | 9857231 |
| oligoribonucleotides containing 8-oxo-7,8-dihydroguanosine and 8-oxo-7,8-dihydro-2'-o-methylguanosine: synthesis and base pairing properties. | 7,8-dihydroguanosine(8-oxog) and 7,8-dihydro-2'-o-methylguanosine (8-oxog-me) were chemically synthesized. oligoribonucleotides which contain 8-oxog or 8-oxog-me were synthesized. incorporation of nucleotides opposite 8-oxog and 8-oxog-me with dntp by mmlv reverse transcriptase during cdna synthesis was characterized. | 1998 | 9871516 |
| novel tools for production and purification of recombinant adenoassociated virus vectors. | standard protocols for the generation of adenoassociated virus type 2 (aav-2)-based vectors for human gene therapy applications require cotransfection of cells with a recombinant aav (raav) vector plasmid and a packaging plasmid that provides the aav rep and cap genes. the transfected cells must also be overinfected with a helper virus, e.g., adenovirus (ad), which delivers multiple helper functions necessary for raav production. therefore, raav stocks produced using these protocols are contamin ... | 1998 | 9874273 |
| redundant proteolytic activation of a viral superantigen. | proteolytic activation of viral superantigens (vsags)4 expressed in chinese hamster ovary (cho) cells is required for t cell stimulation, and is mediated primarily by the protein convertase (pc) furin. three pc recognition sites are highly conserved in vsags, but it was not known which sites are required for pc dependent vsag activation. moreover, because the pc recognition sites are not conserved in all functional vsags it was possible that activation could occur by processing at any of several ... | 1998 | 9881685 |
| systemic antibodies can inhibit mouse mammary tumor virus-driven superantigen response in mucosa-associated lymphoid tissues. | many mucosal pathogens invade the host by initially infecting the organized mucosa-associated lymphoid tissue (o-malt) such as peyer's patches or nasal cavity-associated lymphoid tissue (nalt) before spreading systemically. there is no clear demonstration that serum antibodies can prevent infections in o-malt. we have tested this possibility by using the mouse mammary tumor virus (mmtv) as a model system. in peripheral lymph nodes or in peyer's patches or nalt, mmtv initially infects b lymphocyt ... | 1999 | 9882389 |
| kinetic properties and stereospecificity of the monomeric dutpase from herpes simplex virus type 1. | kinetic properties of the monomeric enzyme dutpase from herpes simplex virus type 1 (hsv) were investigated and compared to those previously determined for homotrimeric dutpases of bacterial and retroviral origins. the hsv and escherichia coli dutpases are equally potent as catalysts towards the native substrate dutp with a kcat/k(m) of about 10(7) m(-1) s(-1) and a k(m) of 0.3 microm. however, the viral enzymes are less specific than the bacterial enzyme. the hsv and e. coli dutpases show the s ... | 1998 | 9883909 |
| cytolytic activities of il-2 activated nk cells from mmtv/v-ha-ras transgenic oncomice during tumor progression. | il-2 activated natural killer (a-nk) cells have the capacity to infiltrate metastatic tumors and lyse tumor cells. nevertheless, adoptive immunotherapy with lymphokine-activated killer cells has been only modestly effective in the clinic and has not routinely provided long-term survival in patients with established cancer metastases. this may indicate the need for more carefully investigating the role of effector cells of the immune response, including a-nk cells, in models of tumor progression. ... | 1998 | 9891221 |
| treatment with farnesyl-protein transferase inhibitor induces regression of mammary tumors in transforming growth factor (tgf) alpha and tgf alpha/neu transgenic mice by inhibition of mitogenic activity and induction of apoptosis. | mouse mammary tumor virus-transforming growth factor alpha (mmtv-tgf alpha) and mmtv-tgf alpha/neu transgenic mice develop mammary tumors after a long latency and therefore provide useful model systems for breast cancer with its recognized activation of receptor tyrosine kinase signaling. we used these mice to study the antitumor effect of l-744,832 (fti), a potent and selective inhibitor of farnesyl-protein transferase, and hence of ras function. a total of 55 mice were assigned randomly to tre ... | 1999 | 9918200 |
| enhancement of phosphorylation and transcriptional activity of the glucocorticoid receptor in human synovial fibroblasts by nimesulide, a preferential cyclooxygenase 2 inhibitor. | to examine the effect of 2 nonsteroidal antiinflammatory drugs (nsaids), nimesulide (nim), a preferential cyclooxygenase 2 (cox-2) inhibitor, and naproxen (nap), on the functional parameters and transcriptional activity of the glucocorticoid receptor (gr) system in cultured human synovial fibroblasts (hsf). | 1999 | 9920026 |
| diversity of human endogenous retrovirus class ii-like sequences. | class ii human endogenous retroviruses (hervs), often referred to as mouse mammary tumour virus (mmtv)-like or herv-k elements, have similarities to several animal infectious retroviruses. single clones from each of nine class ii herv groups (nmwv 1 to nmwv 9), isolated from a human breast cancer cell genomic library, were sequenced over a 244 bp stretch of the conserved reverse transcriptase region. these sequences were aligned to related exogenous and endogenous retroviruses and a phylogenetic ... | 1999 | 9934709 |
| [the role of apc in colonic cancerogenesis: zeroing in on myc]. | the apc gene is mutated both in familial adenomatous polyposis (fap) and sporadic colorectal cancers. it had been previously shown that the apc gene product interacts with beta-catenin, a key element in the wnt-1 signaling pathway. this pathway is initiated by the growth factor wnt-1 and ends up in the nucleus where it activates transcription factors of the lef/tcf family although the targets of the latter were still unknown. this has just been accomplished by the identification of the c-myc onc ... | 1998 | 9951419 |
| dna synthesis exhibited by the reverse transcriptase of mouse mammary tumor virus: processivity and fidelity of misinsertion and mispair extension. | we have recently expressed in bacteria an enzymatically active reverse transcriptase (rt) of mouse mammary tumor virus (mmtv), a mammalian retrovirus with a typical b-type morphology [taube, r., loya, s., avidan, o., perach, m. & hizi, a. (1998) biochemical j. 329, 579-587]. the purified recombinant protein was shown to possess the catalytic activities characteristic of retroviral reverse transcriptases. in the present study, we have analyzed two basic parameters characteristic of the dna polyme ... | 1998 | 9990322 |
| transfer rna modification status influences retroviral ribosomal frameshifting. | the possibility of whether trnas with and without a highly modified base in their anticodon loop may influence the level of retroviral ribosomal frameshifting was examined. rabbit reticulocyte lysates were programmed with mrna encoding uuu or aac at the frameshift site and the corresponding phe trna with or without the highly modified wyebutoxine (y) base on the 3' side of its anticodon or asn trna with or without the highly modified queuine (q) base in the wobble position of its anticodon added ... | 1999 | 10049815 |
| antisense downregulation of a mouse mammary tumor virus activated protooncogene in mouse mammary tumor cells reverses the malignant phenotype. | activation of the protooncogene wnt-1 by insertion of the mouse mammary tumor virus (mmtv) is known to cause mammary tumors in mice. wnt-1 expression in mammary glands has been postulated to confer direct local growth stimulation of mammary epithelial cells leading to their acquisition of a preneoplastic state. wnt-1 expression also induces morphological alterations in cultured normal mammary cells. however, it has not been determined whether or not transformed mammary cells require continuous w ... | 1999 | 10049829 |
| rapid and sensitive reporter gene assays for detection of antiandrogenic and estrogenic effects of environmental chemicals. | reports on increasing incidences in developmental abnormalities of the human male reproductive tract and the recent identifications of environmental chemicals with antiandrogenic activity necessitate the screening of a larger number of compounds in order to get an overview of potential antiandrogenic chemicals present in our environment. thus, there is a great need for an effective in vitro screening method for (anti)androgenic chemicals. we have developed a rapid, sensitive, and reproducible re ... | 1999 | 10053169 |
| nuclear factor i-mediated repression of the mouse mammary tumor virus promoter is abrogated by the coactivators p300/cbp and src-1. | to better understand the function of nuclear factor i (nfi) proteins in transcription, we have used transient transfection assays to assess transcriptional modulation by nfi proteins on the nfi-dependent mouse mammary tumor virus (mmtv) promoter. expression of nfi-c or nfi-x, but not nfi-a or nfi-b proteins, represses glucocorticoid induction of the mmtv promoter in hela cells. repression is dna binding-independent as a deletion construct expressing the nh2-terminal 160 residues of nfi-c repress ... | 1999 | 10066764 |
| b cell response after mmtv infection: extrafollicular plasmablasts represent the main infected population and can transmit viral infection. | the immune response to mouse mammary tumor virus (mmtv) relies on the presentation of an mmtv-encoded superantigen by infected b cells to superantigen-specific t cells. the initial extrafollicular b cell differentiation involved the generation of b cells expressing low levels of b220. these b220low b cells corresponded to plasmablasts that expressed high levels of cd43 and syndecan-1 and were cd62 ligand- and igd-. viral dna was detected nearly exclusively in these b220low b cells by pcr, and re ... | 1999 | 10072493 |
| differential localization and activity of the a- and b-forms of the human progesterone receptor using green fluorescent protein chimeras. | subcellular localization and transcriptional activity of green fluorescent protein-progesterone receptor a and b chimeras (gfp-pra and gfp-prb) were examined in living mammalian cells. both gfp-pra and b chimeras were found to be similar in transcriptional activity compared with their non-gfp counterparts. gfp-pra and pra were both weakly active, while gfp-prb and prb gave a 20- to 40-fold induction using a reporter gene containing the full-length mouse mammary tumor virus long-terminal repeat l ... | 1999 | 10076994 |
| distinguishing androgen receptor agonists and antagonists: distinct mechanisms of activation by medroxyprogesterone acetate and dihydrotestosterone. | natural and pharmacological androgen receptor (ar) ligands were tested for their ability to induce the ar nh2-terminal and carboxyl-terminal (n/c) interaction in a two-hybrid protein assay to determine whether n/c complex formation distinguishes in vivo ar agonists from antagonists. high-affinity agonists such as dihydrotestosterone, mibolerone, testosterone, and methyltrienolone at concentrations between 0.1 and 1 nm induce the n/c interaction more than 40-fold. the lower affinity anabolic ster ... | 1999 | 10077001 |
| regulation of actin organisation by tgf-beta in h-ras-transformed fibroblasts. | the actin cytoskeleton undergoes architectural changes during the processes of cell transformation and tumourigenesis. transforming growth factors beta arrest cell cycle progression, regulate differentiation and modulate the onset of oncogenesis and tumourigenesis. here, we investigated the direct role of transforming growth factor beta-1 in altering the transformed phenotype and regulating the actin organisation of oncogenic fibroblasts that constitutively or inducibly express the h-ras oncogen ... | 1999 | 10085252 |
| characterization of human mmtv-like (hml) elements similar to a sequence that was highly expressed in a human breast cancer: further definition of the hml-6 group. | previously, we found a retroviral sequence, hml-6.2bc1, to be expressed at high levels in a multifocal ductal breast cancer from a 41-year-old woman who also developed ovarian carcinoma. the sequence of a human genomic clone (hml-6.28) selected by high-stringency hybridization with hml-6.2bc1 is reported here. it was 99% identical to hml-6.2bc1 and gave the same restriction fragments as total dna. hml-6.28 is a 4.7-kb provirus with a 5'ltr, truncated in rt. data from two similar genomic clones a ... | 1999 | 10087223 |
| chronic modulation of the tcr repertoire in the lymphoid periphery. | using tcr v beta 5 transgenic mice as a model system, we demonstrate that the induction of peripheral tolerance can mold the tcr repertoire throughout adult life. in these mice, three distinct populations of peripheral t cells are affected by chronic selective events in the lymphoid periphery. first, cd4+v beta 5+ t cells are deleted in the lymphoid periphery by superantigens encoded by mouse mammary tumor viruses-8 and -9 in an mhc class ii-dependent manner. second, mature cd8+v beta 5+ t cells ... | 1999 | 10092762 |
| characterization of two infectious mouse mammary tumour viruses: superantigenicity and tumorigenicity. | mouse mammary tumour virus (mmtv) is a type b retrovirus that causes mammary tumours in susceptible mice. mmtv encodes a superantigen (sag) that has the property of stimulating t-cell populations expressing a particular variable region of the t-cell receptor (tcr) beta chain (vbeta) and needs to be presented in the context of major histocompatibility complex (mhc) class ii molecules. previously, we described two exogenous mmtv, mmtv balb14, which encodes a superantigen that induces the deletion ... | 1999 | 10102644 |
| transcriptional regulation: switching circuitry. | proteins of the swi/snf family disrupt chromatin, hydrolysing atp in the process. how they do so is still mysterious, but recent studies indicate that they can be targeted to the nuclear infrastructure and to particular genes, where they cooperate with other enzymes to activate or repress transcription. | 1999 | 10209086 |
| a composite enhancer element directing tissue-specific expression of mouse mammary tumor virus requires both ubiquitous and tissue-restricted factors. | mouse mammary tumor virus (mmtv) expression is restricted primarily to mammary epithelial cells. sequences responsible for both the mammary-specific expression of mmtv and the activation of cellular oncogenes are located within two enhancer elements at the 5'-end of the long terminal repeat. whereas the ban2 enhancer (-1075 to -978) has been well characterized, the mammary-specific enhancer of mmtv from -956 to -862 has only recently been recognized as a key determinant of mammary-specific oncog ... | 1999 | 10212264 |
| a mouse mammary tumor virus-wnt-1 transgene induces mammary gland hyperplasia and tumorigenesis in mice lacking estrogen receptor-alpha. | estrogens have important functions in mammary gland development and carcinogenesis. to better define these roles, we have used two previously characterized lines of genetically altered mice: estrogen receptor-alpha (er alpha) knockout (erko) mice, which lack the gene encoding er alpha, and mouse mammary virus tumor (mmtv)-wnt-1 transgenic mice (wnt-1 tg), which develop mammary hyperplasia and neoplasia due to ectopic production of the wnt-1 secretory glycoprotein. we have crossed these lines to ... | 1999 | 10213494 |
| the comparative pathology of human and mouse mammary glands. | the mouse has emerged as a primary animal model for human breast cancer because the mammary glands of the two species are very similar in structure and function. in this regard the tdlu and la have similar morphology. the mouse, infected by mmtv, develops "spontaneous" tumors with specific but limited tumor phenotypes. the advent of genetic manipulation has created transgenic mice that develop hyperplasias and tumors morphologically and cytochemically comparable to lesions in humans. even experi ... | 1999 | 10219910 |
| in vivo elimination of viral superantigen-activated cd4+ t cells: apoptosis occurs at a distance from the activation site. | local injection of mouse mammary tumor virus (mmtv) induces a local immune response, with activation of viral superantigen (vsag)-specific t cell subsets followed by their clonal deletion. we investigated the fate of vsag-reactive t cells following footpad injection of mmtv(sw) to mice. activated t cells accumulated in draining lymph nodes. however, we demonstrated that apoptosis did not occur at the activation site, on the contrary of what has been shown after bacterial sag activation. although ... | 1999 | 10221649 |
| development of t-b cell collaboration in neonatal mice. | the neonatal immune response is impaired during the first weeks after birth. to obtain a better understanding of this immaturity, we investigated the development of t cell interactions with b cells in mice. for this purpose, we analyzed the immune response to three t-dependent antigens in vivo: (i) the polyclonal antibody response induced by vaccinia virus; (ii) the production of polyclonal and specific antibodies following immunization with hapten-carrier conjugates; (iii) the mouse mammary tum ... | 1999 | 10221656 |
| two different gene elements are required for glucose regulation of s14 transcription. | carbohydrate feeding increases the transcriptional activity of the hepatic s14 gene. the region of the s14 promoter between -1384/-1275 contributes to the transcriptional regulation by carbohydrate. a previously identified element (-1303/-1289) within this region is required but is not sufficient for the carbohydrate effect. therefore, we ligated -1384/-1275 to a heterologous promoter and created mutants in this region to identify other potential responsive sequences. we found that mutation with ... | 1999 | 10221766 |
| preneoplastic mammary tumor markers: cripto and amphiregulin are overexpressed in hyperplastic stages of tumor progression in transgenic mice. | amphiregulin (ar) and cripto (cr) are autocrine growth factors for mammary cells and both have been observed to exhibit high expression in human mammary tumors, in contrast with adjacent tissues. to investigate whether ar and cr play roles in the progression of mammary cell proliferation to unregulated growth and tumor formation, the levels of expression were examined in transgenic mice (tgm) that over-express several different oncogenes: mmtv-polyoma virus middle t antigen (mmtv-pymt), mmtv-c-e ... | 1999 | 10225449 |
| intracisternal type a particle-mediated activation of the notch4/int3 gene in a mouse mammary tumor: generation of truncated notch4/int3 mrnas by retroviral splicing events. | the int3 oncogene was discovered as a frequent target in mouse mammary tumor virus-induced mammary tumors and encodes the intracellular domain of a notch4/int3 protein. in one spontaneous mammary tumor, no. 9, that developed in a balb/c mouse, we have found an insertion of a 1.2-kb sequence, consisting of a 5' long terminal repeat and gag sequences of an intracisternal type a particle (iap) as well as an extra copy of the notch4/int3 genomic sequences containing exons 23 and 24, into the intron ... | 1999 | 10233982 |
| evidence for an rna pseudoknot loop-helix interaction essential for efficient -1 ribosomal frameshifting. | rna pseudoknots are structural elements that participate in a variety of biological processes. at -1 ribosomal frameshifting sites, several types of pseudoknot have been identified which differ in their organisation and functionality. the pseudoknot found in infectious bronchitis virus (ibv) is typical of those that possess a long stem 1 of 11-12 bp and a long loop 2 (30-164 nt). a second group of pseudoknots are distinguishable that contain stems of only 5 to 7 bp and shorter loops. the nmr str ... | 1999 | 10329145 |
| ku antigen-dna conformation determines the activation of dna-dependent protein kinase and dna sequence-directed repression of mouse mammary tumor virus transcription. | mouse mammary tumor virus (mmtv) transcription is repressed by dna-dependent protein kinase (dna-pk) through a dna sequence element, nre1, in the viral long terminal repeat that is a sequence-specific dna binding site for the ku antigen subunit of the kinase. while ku is an essential component of the active kinase, how the catalytic subunit of dna-pk (dna-pkcs) is regulated through its association with ku is only beginning to be understood. we report that activation of dna-pkcs and the repressio ... | 1999 | 10330147 |
| elevated frequency of loss of heterozygosity in mammary tumors arising in mouse mammary tumor virus/neu transgenic mice. | loss of heterozygosity (loh) analysis was performed on 62 mammary tumors that were induced in (balb/c x c57bl/6)f1 mouse mammary tumor virus/neu transgenic mice. eighty-six simple sequence length polymorphism markers were used to cover all of the somatic chromosomes. frequency of loh was observed to be significant for chromosomes 4 (50%), 19 (32%), and 8 (21%). on chromosome 4, at least three distinct regions of allelic deletions could be identified: one proximal to 22 cm; the second close to th ... | 1999 | 10344755 |
| suppression subtractive hybridization: a versatile method for identifying differentially expressed genes. | a new and highly effective method, termed suppression subtractive hybridization (ssh), has been developed for the generation of subtracted cdna libraries. it is based primarily on a technique called suppression pcr, and combines normalization and subtraction in a single procedure. the normalization step equalizes the abundance of cdnas within the target population and the subtraction step excludes the common sequences between the target and driver populations. as a result only one round of subtr ... | 1999 | 10349654 |
| sjögren's syndrome in mice carrying the ipr(cg) gene and the therapeutic efficacy of an immunosuppressive agent fk506. | the influence of the ipr(cg) gene on the development of sjögren's syndrome was followed up to 5 months of age in male and female mice of mrl, cba and c3h strains. in mrl-ipr(cg) mice, focal mononuclear cell infiltration started at 2 months and became conspicuous after 3 months of age in the lacrimal and submandibular glands but was minimal in the parotid and sublingual glands, even at 5 months of age, without any apparent sex effects found. in cba and c3h mice carrying the ipr(cg) gene, this man ... | 1999 | 10355966 |
| chronic deletion, escape from deletion and activation of mouse mammary tumor virus superantigen-reactive t cells in c57bl/10 mice. | though c57bl/10 mice express the mouse mammary tumor virus superantigens (sag) encoded by mtv-8 and mtv-9, it has been thought that these sag do not bind to the mhc class ii molecule h2-ab and consequently do not affect the t cell repertoire. however, we show that cells bearing tcr vbeta chains specific for mtv-8 and -9 sag are chronically deleted in c57bl/10 mice. thymocytes and peripheral t cells escaping deletion by mtv sag display a small reduction in the level of cell surface cd4. t cells e ... | 1999 | 10359099 |
| functional and phenotypic analysis of thymic b cells: role in the induction of t cell negative selection. | the phenotype of mouse thymic b cells and their capacity to induce t cell negative selection in vitro were analyzed. thymic b cells expressed b cell markers such as igm, fc gamma receptor, cd44, heat-stable antigen, lfa-1 and cd40. in addition, they were positive for the activation molecule cd69 and displayed high levels of b7-2. although thymic b cells expressed cd5 on their surface, no cd5-specific mrna was detected. moreover, thymic b cells induced a stronger deletion of tcr-transgenic (tg) t ... | 1999 | 10359114 |
| concurrent deregulation of gelsolin and cyclin d1 in the majority of human and rodent breast cancers. | decreased gelsolin and increased cyclin d1 are among the most common defects found in human and rodent breast cancers. our purpose was to determine the frequency of concurrence of these 2 alterations in this malignancy. our results demonstrate that gelsolin protein and mrna were significantly reduced in 80-100% of rodent mammary carcinomas that developed spontaneously, following oncogene introduction, or after treatment with viral, chemical or hormonal agents. the reduction in gelsolin most like ... | 1999 | 10362141 |
| differences of milk-transmitted murine mammary tumor virus (mmtv) among mouse strains. | to clarify the oncological differences of milk-transmitted murine mammary tumor virus (mmtv) in various strains, balb/c mice were foster-nursed on c3h/he, gr, ddd, ddd/1-mtv-2/mtv-2 and fm strains and observed for the development and morphology of mammary tumors, followed by testing tumors for pregnancy dependence (pd) after transplantation. mmtv were different in tumorigenicity and morphology and pd of induced tumors among the mouse strains. these differences of mmtv appeared not to be parallel ... | 1999 | 10363169 |
| exonuclease iii as a probe of chromatin structure in vivo. | | 1999 | 10372383 |
| solution structure and thermodynamics of a divalent metal ion binding site in an rna pseudoknot. | identification and characterization of a metal ion binding site in an rna pseudoknot was accomplished using cobalt (iii) hexammine, co(nh3)63+, as a probe for magnesium (ii) hexahydrate, mg(h2o)62+, in nuclear magnetic resonance (nmr) structural studies. the pseudoknot causes efficient -1 ribosomal frameshifting in mouse mammary tumor virus. divalent metal ions, such as mg2+, are critical for rna structure and function; mg2+preferentially stabilizes the pseudoknot relative to its constituent hai ... | 1999 | 10373367 |
| equilibrium unfolding pathway of an h-type rna pseudoknot which promotes programmed -1 ribosomal frameshifting. | the equilibrium unfolding pathway of a 41-nucleotide frameshifting rna pseudoknot from the gag-pro junction of mouse intracisternal a-type particles (miap), an endogenous retrovirus, has been determined through analysis of dual optical wavelength, equilibrium thermal melting profiles and differential scanning calorimetry. the miap pseudoknot is an h-type pseudoknot proposed to have structural features in common with the gag-pro frameshifting pseudoknots from simian retrovirus-1 (srv-1) and mouse ... | 1999 | 10373368 |
| homeoproteins cdp and satb1 interact: potential for tissue-specific regulation. | homeoproteins are known to participate in development and cell type specification. the homeoproteins ccaat displacement protein (cdp) and special at-rich sequence binding protein 1 (satb1) have been shown to bind to nuclear matrix-associated regions and to act as repressors of many cellular genes. moreover, binding of satb1 to the mouse mammary tumor virus (mmtv) promoter region dramatically affects the tissue-specific transcription of this retrovirus. because protein-protein interactions are a ... | 1999 | 10373541 |
| characterization of the drosophila ortholog of mouse eif-3p48/int-6. | the mouse mammary tumor virus (mmtv) has been shown to integrate frequently into int-6 in mmtv-induced mouse mammary tumors. the int6 gene has been highly conserved through evolution and has recently been shown to encode the p48 component of the eucaryotic translation initiation factor 3 (eif-3) complex. we report here the isolation of the drosophila eif-3p48/int-6. the gene comprises three exons within 1.8kb of genomic dna located at cytogenetic position 73c2 in the drosophila genome. the 1.5kb ... | 1999 | 10375641 |
| a recurring pattern of chromosomal aberrations in mammary gland tumors of mmtv-cmyc transgenic mice. | mice carrying the mmtv-cmyc transgene develop mammary tumors at 9 to 12 months of age. little is known about karyotypic changes in this model of human breast cancer. we have developed and applied molecular cytogenetic techniques to study chromosomal aberrations that occur in these tumors, namely, comparative genomic hybridization and spectral karyotyping. cell lines from eight tumors were established and analyzed, four of which carried a heterozygous p53 mutation. all of the tumor cell lines rev ... | 1999 | 10379871 |
| thiazolidinedione effects on glucocorticoid receptor-mediated gene transcription and differentiation in osteoblastic cells. | the glucocorticoid receptor (gr) and peroxisome proliferator-activated receptors (ppars) play important roles in the differentiation of mesenchymal cells. glucocorticoids acting via the gr promote osteoblastic differentiation of bone marrow stromal cells, whereas ppar ligands induce these cells to become adipocytes. to explore potential interactions between ppar and gr pathways in osteoblasts, we studied the interaction between ppar subtype-selective ligands and dexamethasone (dex) in a murine c ... | 1999 | 10385421 |
| development of hyperplasias, preneoplasias, and mammary tumors in mmtv-c-erbb-2 and mmtv-tgfalpha transgenic rats. | human cdnas corresponding to two epidermal growth factor-related products that are overexpressed in human breast cancers, that for c-erbb-2 (her-2) and for transforming growth factor alpha (tgfalpha), have been cloned downstream of the mouse mammary tumor virus (mmtv) long terminal repeat promoter and injected into the pronucleus of fertilized oocytes of sprague-dawley rats to produce transgenic offspring. expression of the transgenic mrnas is not detectable in mammary tissue from virgin transge ... | 1999 | 10393862 |
| synergism between mild hyperthermia and interferon-beta gene expression. | in the present study, the synergistic effect of mild hyperthermia in combination with gene expression of interferon-beta (ifn-beta) was examined in vitro in the human glioma cell line u87mg. the cells transiently expressed the ifn-beta gene under the control of the mouse mammary tumor virus promoter and were then subjected to temperature elevation (41 degrees c for 1 h). in terms of the cell killing effect, the optimum scheme was obtained by transfection for 4 days before hyperthermia, i.e. rate ... | 1999 | 10395172 |
| timp-1 is important for epithelial proliferation and branching morphogenesis during mouse mammary development. | the dynamic process of mammary ductal morphogenesis depends on regulated epithelial proliferation and extracellular matrix (ecm) turnover. epithelial cell-matrix contact closely dictates epithelial proliferation, differentiation, and survival. despite the fact that tissue inhibitors of metalloproteinases (timps) regulate ecm turnover, their function in mammary morphogenesis is unknown. we have delineated the spatiotemporal expression of all timps (timp-1 to timp-4) during discrete phases of muri ... | 1999 | 10395785 |
| interplays between mouse mammary tumor virus and the cellular and humoral immune response. | mouse mammary tumor virus has developed strategies to exploit the immune response. it requires vigorous immune stimulation to achieve efficient infection. the infected antigen-presenting cells present a viral superantigen on the cell surface which stimulates strong cd4-mediated t-cell help but cd8 t-cell responses are undetectable. despite the high frequency of superantigen-reactive t cells, the superantigen-induced immune response is comparable to classical antigen responses in terms of t-cell ... | 1999 | 10399081 |
| expression of mouse mammary tumor virus superantigen mrna in the thymus correlates with kinetics of self-reactive t-cell loss. | mouse mammary tumor virus (mmtv) encodes a superantigen (sag) that is expressed at the surface of antigen-presenting cells in conjunction with major histocompatibility complex (mhc) type ii molecules. the sag-mhc complex is recognized by entire subsets of t cells, leading to cytokine release and amplification of infected b and t cells that carry milk-borne mmtv to the mammary gland. expression of sag proteins from endogenous mmtv proviruses carried in the mouse germ line usually results in the d ... | 1999 | 10400761 |
| comparison of chromatin remodeling and transcriptional activation of the mouse mammary tumor virus promoter by the androgen and glucocorticoid receptor. | we examined the interaction between the androgen (ar) and glucocorticoid receptor (gr) at the transcriptional level using mouse fibroblast cell lines harboring an integrated mouse mammary tumor virus (mmtv) promoter. we found that the ar, after induction with dihydrotestosterone (dht), caused a progressive increase in mmtv-cat reporter activity over 72 h which was correlated to an increase in chromatin remodeling of the mmtv promoter in the vicinity of the hormone response element (hre). in cont ... | 1999 | 10413595 |
| isolation and characterization of ara160 as the first androgen receptor n-terminal-associated coactivator in human prostate cells. | the androgen receptor (ar) is a member of the steroid receptor superfamily that may require coactivators for proper or maximal transactivation. using a purified ar n-terminal peptide as a probe to screen the human testis expression library, we identified an androgen-enhanced ar n-terminal-associated protein ara160, which consists of 1,093 amino acids with an apparent molecular mass of 160 kda. sequence comparison in genbank(tm) reveals that ara160 shares an identical sequence with a hiv-1 tata e ... | 1999 | 10428808 |
| preferential binding of mouse mammary tumor virus to b lymphocytes. | mouse mammary tumor virus (mmtv) has been shown to preferentially infect b lymphocytes in vivo. we have used recombinant envelope-coated fluospheres and highly purified mmtv particles to study the distribution of the viral receptors on fresh mouse lymphocytes. a preferential dose-dependent binding to b lymphocytes was observed which could be competed with neutralizing antibodies. in contrast, t-lymphocyte binding remained at background levels. these results strongly suggest a higher density of v ... | 1999 | 10438888 |
| two-step synergism between the progesterone receptor and the dna-binding domain of nuclear factor 1 on mmtv minichromosomes. | in contrast to its behavior as naked dna, the mmtv promoter assembled in minichromosomes can be activated synergistically by the progesterone receptor and nf1 in a process involving atp-dependent chromatin remodeling. the dna-binding domain of nf1 is required and sufficient for stable occupancy of all receptor-binding sites and for functional synergism. activation of purified minichromosomes is observed in the absence of swi/snf and can be enhanced by recombinant iswi. receptor binding to minich ... | 1999 | 10445026 |
| overproduction of histone h1 variants in vivo increases basal and induced activity of the mouse mammary tumor virus promoter. | balb/c 3t3 cell lines containing integrated copies of the mmtv promoter driving a reporter gene were constructed. expression vectors in which either of two h1 variants, h10 or h1c, were under control of an inducible promoter were introduced into these lines. surprisingly, overproduction of either variant resulted in a dramatic increase in basal and hormone-induced expression from the mmtv promoter. h1 overproduction also slowed the loss of mmtv promoter activity associated with prolonged hormone ... | 1999 | 10454644 |
| luciferase reporter gene vectors that lack potential ap-1 sites. | | 1999 | 10457818 |