| [superantigens and their behavior in the immune response]. | superantigens are a group of molecules produced by bacteria, viruses and parasites that stimulate t lymphocytes in a very potent way. they join the tcr-hla complex from the outside, not through the classical peptide-bound mechanism, so that they can easily trigger the citokyne production network and produce tissue damage, they can also lead to clonal anergy over the cd4 t cell subpopulations (th0/th1/th2). | 1996 | 8901035 |
| mouse mammary tumor virus production by thymic epithelial cells in vivo. | exogenous mouse mammary tumor viruses (mmtv) replicate in the mammary glands of infected females, and so infect the suckling pups. we have previously shown that the virus is rapidly disseminated to all the lymphoid organs, including the thymus. the present electron microscope immunohistochemical study describes the viral production site in the thymus. viral buds and viral proteins were restricted to the thymus medullary epithelial cells. mmtv-encoded proteins were identified on the free viral pa ... | 1996 | 8921961 |
| the potential roles of endogenous retroviruses in autoimmunity. | endogenous retroviruses (ervs) are estimated to comprise up to 1% of human dna. while the genome of many ervs is interrupted by termination codons, deletions or frame shift mutations, some ervs are transcriptionally active and recent studies reveal protein expression or particle formation by human ervs. ervs have been implicated as aetiological agents of autoimmune disease, because of their structural and sequence similarities to exogenous retroviruses associated with immune dysregulation and th ... | 1996 | 8930674 |
| involvement of the tpl-2/cot oncogene in mmtv tumorigenesis. | we report for the first time a relationship between the tpl-2/cot oncogene and mouse mammary tumor virus (mmtv) associated transformation of mammary gland cells. a sub-genomic library generated from a primary mammary gland tumor yielded a novel mmtv integration site which disrupted the tpl-2/cot proto-oncogene between exons 7 and 8. comparison of a cell line derived from normal mammary gland (comma-d) and a cell line established from an mmtv induced mammary tumor (gr) demonstrated similar rearra ... | 1996 | 8934549 |
| characterization of an nf-1/ctf family member as a functional activator of the mouse mammary tumor virus long terminal repeat 5' enhancer. | the long terminal repeat of the mouse mammary tumor virus restricts virus expression primarily to the mammary epithelium. the extreme 5' end of the long terminal repeat contains an enhancer that has been associated with tissue-specific expression of the virus. a total of six functional cis-acting elements have been identified in the enhancer. although proteins binding to these elements have been reported, only one has been identified; this factor, mp5, is identical or closely related to the tran ... | 1996 | 8940131 |
| the mouse mammary tumor virus env gene is the source of a cd8+ t-cell-stimulating peptide presented by a major histocompatibility complex class i molecule in a murine thymoma. | cd8+ cytotoxic t cells recognize their targets by the presence of unique peptide bound to a major histocompatibility complex (mhc) class i molecules on the cell surface. the mhc molecules normally display thousands of distinct peptides, making it difficult to identify individual antigenic peptides, their protein precursors, and their relative importance in the t-cell response. here we used the el-4 tumor-specific lacz-inducible kz30.6 t cell as a probe for detecting the peptide/mhc ligand that w ... | 1996 | 8943048 |
| epigenetic modification of transgenes under the control of the mouse mammary tumor virus ltr: tissue-dependent influence on transcription of the transgenes. | transgenic mice expressing human urokinase, as well as animals expressing human urokinase receptor under the control of the murine mammary tumor virus (mmtv) long terminal repeat, were established. in the vast majority of the founder animals and their descendants, the transgene was completely methylated, corresponding to down-regulation of transgene expression in the mammary gland. two lineages with human urokinase receptor as the transgene with mixed methylation of the transgenes were analyzed ... | 1996 | 8960372 |
| reduced androgen receptor gene expression with first exon cag repeat expansion. | the molecular basis for partial androgen insensitivity associated with adult onset spinal/bulbar muscular atrophy was investigated by transient transfection of human androgen receptor (ar) expression vectors containing increasing cag repeat lengths in the first exon. an inverse relationship was observed between cag repeat length and ar mrna and protein levels. trinucleotide repeat lengths of 43 and 65 associated with spinal/bulbar muscular atrophy decreased ar mrna and protein levels but did not ... | 1996 | 8961263 |
| superantigens in disease. | | 1996 | 8966656 |
| chromatin structure and the regulation of gene expression: remodeling at the mmtv promoter. | the role of the various levels of chromatin organization in the control of eukaryotic gene expression is discussed on the basis of recent advances in our understanding of chromatin structure in well-defined model systems. particular attention is devoted to the precise structure and the possible functions of positioned nucleosomes and to the enzymatic mechanism of nucleosome remodeling. some of the principles involved are illustrated with genomic footprinting results obtained with the mouse mamma ... | 1996 | 8974015 |
| insertion of metal-responsive elements increases the inducibility of the mouse mammary tumor virus promoter. | the promoter of the mouse mammary tumor virus (mmtv) is commonly used in inducible mammalian expression vectors. we have modified this promoter by inserting metal-responsive elements (mre) at different sites. surprisingly, mmtv promoters containing mre 5' with respect to the glucocorticoid responsive elements (gre), were not induced by metal ions. however, in the simultaneous presence of dexamethasone and metal ions, the modified promoters displayed a significantly increased transcriptional stre ... | 1996 | 8982085 |
| tgf beta regulation of cell proliferation. | the beta-type transforming growth factors (tgf beta) are potent inhibitors of cell proliferation. the mechanisms of tgf beta growth inhibition have been investigated. in skin keratinocytes, tgf beta 1 rapidly suppresses c-myc expression at the level of transcriptional initiation, and expression of c-myc was shown to be necessary for proliferation of these cells. overexpression of c-myc, using an inducible construct, blocks growth inhibition by tgf beta 1. in 11.5 day p.c. lung bud organ cultures ... | 1994 | 8983080 |
| partial regression, yet incomplete eradication of mammary tumors in transgenic mice by retrovirally mediated hsvtk transfer 'in vivo'. | mice transgenic for the activated rat neu oncogene under the control of the mouse mammary tumor virus long terminal repeat (mmtv-ltr) (neu+ mice), develop breast tumors in 100% of cases. we have previously reported that double transgenic mice obtained from crossing neu+ mice with mice transgenic for the herpes simplex virus thymidine kinase (hsvtk) gene can be used as a suitable model to test the 'suicide gene' strategy for mammary tumor gene therapy in vivo. in the present study, we evaluated t ... | 1996 | 8986442 |
| visualization of multicomponent transcription factor complexes on chromatin and nonnucleosomal templates in vivo. | there is increasing evidence that specific chromatin structures play an important role in the regulation of transcription in eukaryotes. the mouse mammary tumor virus (mmtv) promoter, which is reproducibly assembled into a phased array of six nucleosomes when introduced into cells, represents a particularly well-studied example. the second or b nucleosome of the phased array is disrupted in response to hormone stimulation, allowing the assembly of a preinitiation complex and the activation of tr ... | 1997 | 8993036 |
| naturally occurring selenium compounds in cancer chemoprevention trials: a workshop summary. | evidence from epidemiological studies and a human intervention trial indicates that selenium (se) may have chemopreventive activity in humans. this report summarizes a workshop held by the national cancer institute to address the use of naturally occurring se compounds in future cancer chemoprevention trials. differences in the metabolism of inorganic and organic se compounds can be seen both in the biochemical handling of these forms and in their kinetics in humans. long-term supplementation co ... | 1997 | 8993799 |
| shared promoter elements between a viral superantigen and the major histocompatibility complex class ii-associated invariant chain. | superantigens have the ability to stimulate subsets of t lymphocytes bearing particular t-cell receptor vbeta chains. the best-known viral superantigen is mls, a product of the murine mammary tumor virus (mmtv) sag gene. the mmtv superantigen is not displayed by the virus itself; however, after infection of b lymphocytes, the superantigen is expressed. the resulting immune stimulation is essential for viral transmission. we have analyzed the transcriptional elements which control mls-1 expressio ... | 1997 | 8995647 |
| the dutpases from herpes simplex virus type 1 and mouse mammary tumour virus are less specific than the escherichia coli enzyme. | the enzyme dutpase catalyses the hydrolysis of dutp to dump and pyrophosphate, thereby suppressing incorporation of uracil into dna and providing a pool of dump, the precursor of dttp. hydrolysis of other nucleotides similar in structure to dutp would conceivably be physiologically detrimental and high specificity of the reaction seems to be necessary. in this work, we characterize the substrate specificity of the dutpases from herpes simplex virus type 1 (hsv-1) and mouse mammary tumour virus ( ... | 1996 | 9000104 |
| keratinocyte growth factor induces mammary and prostatic hyperplasia and mammary adenocarcinoma in transgenic mice. | the kinetics of solitary mammary tumor formation in transgenic mice bearing the mmtv-int-2 (fgf3) fusion gene suggest that several genetic events are required for tumorigenesis. in an effort to identify elements that could contribute to this oncogenic process, we used differential display pcr to identify gene products that are strongly and specifically induced in int-2 mammary tumors. using this approach we identified a member of the fgf family, kgf (fgf7), as a gene that is strongly upregulated ... | 1996 | 9000125 |
| increased tumor proliferation and genomic instability without decreased apoptosis in mmtv-ras mice deficient in p53. | we have used an in vivo tumor model to evaluate the consequences of p53 tumor suppressor protein deficiency in a tissue-specific context. by breeding mmtv-ras transgenic mice, which are highly susceptible to the development of mammary and salivary tumors, with p53(-/-) mice, we generated three classes of animals which contained the mmtv-ras transgene but differed in their p53 functional status (ras/p53(+/+), ras/p53(+/-), or ras/p53(-/-)). ras/p53(-/-) mice developed tumors more rapidly than ani ... | 1997 | 9001226 |
| recombinant fusion peptides containing single or multiple repeats of a ubiquitous t-helper epitope are highly immunogenic. | two recombinant mouse mammary tumor virus (mmtv) subunit vaccines have been constructed, in which linear sequences of the envelope gp 52 glycoprotein (ep3) or the superantigen (sag) have been fused to single or multiple repeats of a t-cell epitope (p30) from tetanus toxin. histidine tags or glutathione-s-transferase (gst) sequences have been included in the recombinant peptides in order to facilitate their purification by affinity chromatography. the ep3 or sag recombinant polypeptides with four ... | 1996 | 9010240 |
| estrogen induction of tgf-alpha is mediated by an estrogen response element composed of two imperfect palindromes. | to investigate the molecular mechanisms underlying the two- to three-fold induction of human transforming growth factor-alpha (htgf-alpha) mrna and two- to five-fold induction of htgf-alpha protein observed following estrogen treatment of hormone-responsive human breast cancer cell lines, the htgf-alpha promoter was assayed for ere-like sequences able to mediate estrogen induction of a heterologous gene. transient co-transfection of a chloramphenicol acetyl transferase (cat) construct consisting ... | 1996 | 9010318 |
| mutant and wild-type androgen receptors exhibit cross-talk on androgen-, glucocorticoid-, and progesterone-mediated transcription. | androgen, glucocorticoid, and progesterone receptors (ars, grs, and prs) often can regulate transcription via composite hormone response elements in target genes. we have used artificial and natural mutant ars from patients with androgen resistance to study their effects on dominant negative activity on wild type ar, gr, and pr function on mouse mammary tumor virus (mmtv) and tyrosine aminotransferase (tat) promoters. artificial ars that contained internal deletions within the amino-terminal reg ... | 1997 | 9013763 |
| in vivo generation of 3' and 5' truncated species in the process of c-myc mrna decay. | it has been demonstrated that the half-life of c-myc mrna is modulated in response to physiological agents. the elucidation of the decay process and the identification of the critical steps in the in vivo c-myc mrna degradation pathway can be approached by following the fate of c-myc mrna under the influence of such factors. ifn-alpha was the factor used to modulate c-myc mrna half-life in hela 1c5 cells, a stable clone derived from hela cells. this cell line carries multiple copies of the c-myc ... | 1996 | 9016668 |
| rapamycin potentiates dexamethasone-induced apoptosis and inhibits jnk activity in lymphoblastoid cells. | the immunosuppressant rapamycin (rap) potentiated apoptosis of the murine t lymphoblastoid cell line s49 induced by dexamethasone (dex), while rap by itself did not induce apoptosis of the cells. fk506, in contrast, had no effect on dex-induced apoptosis; moreover, an excess of fk506 reversed the potentiation of apoptosis by rap, indicating that rap exerts its effects through binding to fkbp. both rap and fk506 enhanced the mmtv promoter activity by dexamethasone, suggesting that the potentiatio ... | 1997 | 9016789 |
| glucocorticoid receptor lacking the tau 1 transactivation domain is a gene-specific regulator of the wild-type glucocorticoid-receptor activity. | the glucocorticoid receptor (gr) contains a major transactivation function (tau 1), located in the n-terminal domain. tau 1 contributes to about 80% of the ligand-inducible transcriptional activity of gr. in this study, we show that gr devoid of tau 1 (symbol: see text] gr) can inhibit activation of gene expression by wild-type gr but this does not occur for all target genes. activation of the mouse mammary tumor virus promoter by wild-type gr in transiently transfected chinese hamster ovary (ch ... | 1996 | 9022717 |
| a novel tetracycline-dependent expression vector with low basal expression and potent regulatory properties in various mammalian cell lines. | the tetracycline-dependent expression system has gained increasing popularity for the expression of any gene of interest. careful choice of the expression vector has been suggested to exploit the full potential of this system. a novel tetracycline-sensitive expression vector based on a modified mouse mammary tumor virus promoter achieved considerably improved regulatory properties in a series of cell lines tested under transient and stable conditions. therefore, the applicability of the tetracyc ... | 1997 | 9023121 |
| protein kinase c pathway potentiates androgen-mediated gene expression of the mouse vas deferens specific aldose reductase-like protein (mvdp). | transcription of the mouse vas deferens protein (mvdp) gene, a member of the aldo-keto reductase superfamily, is stimulated by androgens via the androgen responsive element (are) located in the proximal promoter (-111 to -97). we investigated interaction between androgens and the protein kinase c (pkc) signalling pathway. transcriptional regulation was determined by analysis of chloramphenicol acetyltransferase (cat). t47d cells were transiently transfected with 5' flanking mvdp dna promoter seq ... | 1996 | 9027327 |
| androgen-dependent cell cycle arrest and apoptotic death in pc-3 prostatic cell cultures expressing a full-length human androgen receptor. | to assess the function of androgen receptor in androgen-independent prostate cancer cells, human pc-3 prostate carcinoma cells, which lack androgen receptor (ar) expression, were transfected with a full length human ar cdna sequence inserted into an episomal expression vector system. several clonal lines of transfected cells expressing varying levels of a 110 kda ar, as determined by immunoblotting and ligand binding assay, were isolated. the expressed ectopic receptors displayed nuclear binding ... | 1997 | 9027364 |
| sequence-specific dna binding and transcription factor phosphorylation by ku autoantigen/dna-dependent protein kinase. phosphorylation of ser-527 of the rat glucocorticoid receptor. | nre1 is a dna sequence element through which ku antigen/dna-dependent protein kinase (dna-pk) catalytic subunit represses the induction of mouse mammary tumor virus transcription by glucocorticoids. although ku is an avid binder of dna ends and has the ability to translocate along dna, we report that direct sequence-specific ku binding occurs with higher affinity (kd = 0.84 +/- 0.24 nm) than dna end binding. comparison of ku binding to several sequences over which ku can accumulate revealed two ... | 1997 | 9038175 |
| differential regulation of cell cycle characteristics and apoptosis in mmtv-myc and mmtv-ras mouse mammary tumors. | we have used the mmtv-myc and mmtv-ras transgenic mouse mammary tumor models (t. a. stewart et al., cell, 38: 627-637, 1984, and e. sinn et al., cell, 49: 465-475, 1987) to evaluate how the c-myc and v-ha-ras oncogenes influence tumor growth characteristics in vivo. mmtv-myc tumors had much higher levels of spontaneous apoptosis than mmtv-ras tumors, whereas intermediate levels were observed in mmtv-myc/ras tumors. significant differences in cell cycle characteristics were also observed in tumor ... | 1997 | 9044833 |
| paracrine transfer of mouse mammary tumor virus superantigen. | transfer of vsag7, the endogenous superantigen encoded in the mtv7 locus, from mhc class ii to mhc class ii+ cells has been suggested to occur both in vivo and in vitro. this transfer usually leads to the activation and deletion of t cells expressing responsive v beta s. however, there is no direct molecular evidence for such a transfer. we have developed an in vitro system which confirms this property of vsags. vsag7 was transfected into a class ii murine fibroblastic line. coculture of these c ... | 1997 | 9053447 |
| viral superantigen drives extrafollicular and follicular b cell differentiation leading to virus-specific antibody production. | mouse mammary tumor virus (mmtv[sw]) encodes a superantigen expressed by infected b cells. it evokes an antibody response specific for viral envelope protein, indicating selective activation of antigen-specific b cells. the response to mmtv(sw) in draining lymph nodes was compared with the response to haptenated chicken gamma globulin (np-cgg) using flow cytometry and immunohistology. t cell priming occurs in both responses, with t cells proliferating in association with interdigitating dendriti ... | 1997 | 9053455 |
| expression patterns of the four nuclear factor i genes during mouse embryogenesis indicate a potential role in development. | the nuclear factor i (nfi) family of site-specific dna-binding proteins is required for both the cell-type specific transcription of many viral and cellular genes and for the replication of adenovirus dna. although binding sites for nfi proteins within the promoters of several tissue-specific genes have been shown to be essential for their expression, it is unclear which nfi gene products function in specific tissues during development. we have isolated cdnas from all four murine nfi genes (gene ... | 1997 | 9056636 |
| generation of a tumorigenic milk-borne mouse mammary tumor virus by recombination between endogenous and exogenous viruses. | two novel exogenous mouse mammary tumor viruses (mmtv), balb2 and balb14, that encode superantigens (sags) with vbeta2+ and vbeta14+ specificities, respectively, were found in the balb/ct mouse strain. balb/ct females were crossed with akr/j males to generate f1 females. foster nursing of balb/ct mice on (balb/ct x akr/j)f1 mothers resulted in the generation of a new mouse strain, balb/cla, that had acquired a new exogenous mmtv (hereafter called la) with a vbeta6+/vbeta8.1+-t-cell-specific sag. ... | 1997 | 9094666 |
| an mmtv integration site maps near the distal end of mouse chromosome 11. | | 1997 | 9096121 |
| nucleosome-mediated synergism between transcription factors on the mouse mammary tumor virus promoter. | in unstimulated mammalian cells and in saccharomyces cerevisiae, the mouse mammary tumor virus (mmtv) promoter is silent and organized into positioned nucleosomes, one of which encompasses the binding sites for glucocorticoid receptor (gr) and nuclear factor i (nfi). glucocorticoid induction in vivo involves a functional synergism between gr and nfi and simultaneous occupancy of the promoter sites for both proteins that cannot be reproduced on naked dna. the role of chromatin in the process of i ... | 1997 | 9096316 |
| ectopic expression of a-myb in transgenic mice causes follicular hyperplasia and enhanced b lymphocyte proliferation. | the a-myb gene is a transcription factor that shares structural and functional similarities with the v-myb oncogene. to date, v-myb is the only myb gene directly implicated in tumorigenesis, a property attributed to its transactivating ability. recent studies have demonstrated that a-myb, like v-myb, is a potent transcriptional activator, raising the possibility that a-myb may also participate in oncogenesis. to test this hypothesis, we generated fusion constructs that contained the human a-myb ... | 1997 | 9096377 |
| male infertility caused by epididymal dysfunction in transgenic mice expressing a dominant negative mutation of retinoic acid receptor alpha 1. | retinoids are thought to be required for the normal development and maturation of a number of tissues, including most epithelia. the action of retinoids appears to be mediated through the binding to retinoic acid receptors (rars) in the nucleus. the activity of retinoic acid can be inhibited in cells carrying dominant negative mutations of rar alpha. we created transgenic mice expressing a dominant negative mutant of rar alpha driven by the murine mammary tumor virus promoter. expression of the ... | 1997 | 9096882 |
| localization of a negative glucocorticoid response element of the human corticotropin releasing hormone gene. | corticotropin releasing hormone (crh) plays a primary role in mediating suprapituitary activation of the hypothalamic-pituitary-adrenal axis and is an important physiologic target of negative feedback regulation by glucocorticoids. we sought to define cis-acting regions of the crh promoter responsible for camp-dependent activation and glucocorticoid-dependent repression of crh promoter activity. in transiently transfected att-20 cells, camp-dependent transcriptional activation was mediated large ... | 1997 | 9099914 |
| transcription of human endogenous retroviral sequences related to mouse mammary tumor virus in human breast and placenta: similar pattern in most malignant and nonmalignant breast tissues. | the human genome contains a large variety of sequences related to the mouse mammary tumor virus (mmtv). we have investigated the range of expression of human endogenous retroviral sequences (hervs) related to mmtv (human mmtv-like; hml) as rna in 60 breast cancers, 8 nonmalignant breast tissues, and 9 placentas. this was monitored using hml group-specific oligonucleotide probes in hybridizations toward pcr amplificates of hml pol sequences and internal control. the degree of expression of five h ... | 1997 | 9100993 |
| mouse mammary tumor virus and mammary tumorigenesis in wild mice. | the current knowledge of the distribution of the mouse mammary tumor virus (mmtv) proviral genomes and the mechanism of mammary tumorigenesis by mmtv in mice, with the main emphasis on asian feral mice, is reviewed. the relevant earlier discoveries on the mode of mmtv transmission are summarized to provide an outline of the biology of mmtv. finally, the viral etiology of human breast cancer will be discussed. | 1996 | 9110343 |
| a mutant rna pseudoknot that promotes ribosomal frameshifting in mouse mammary tumor virus. | a single a-->g mutation that changes a potential a.u base pair to a g.u pair at the junction of the stems and loops of a non-frameshifting pseudoknot dramatically increases its frameshifting efficiency in mouse mammary tumor virus. the structure of the non-frameshifting pseudoknot apk has been found to be very different from that of pseudoknots that cause efficient frameshifting [kang,h., hines,j.v. and tinoco,i. (1995) j. mol. biol. , 259, 135-147]. the 3-dimensional structure of the mutant pse ... | 1997 | 9115361 |
| a novel human wnt gene, wnt10b, maps to 12q13 and is expressed in human breast carcinomas. | several members of the wnt gene family have been shown to cause mammary tumors in mouse. using degenerate primer polymerase chain reaction (pcr) on human genomic dna, and specific pcr of cdna libraries, we have isolated a wnt gene which has not previously been described in human. the gene is the human homologue of mouse wnt10b, recently shown to be one of the oncogenes cooperating with fgf3 in the development of mouse mammary tumour virus (mmtv) induced mouse mammary carcinomas. the human wnt10b ... | 1997 | 9121776 |
| mouse mammary tumor virus superantigens require n-linked glycosylation for effective presentation to t cells. | mouse mammary tumor viruses (mmtvs) encode superantigens that associate with major histocompatibility complex class ii products on antigen-presenting cells and stimulate t cells in a v beta-specific manner. this t cell activation is critical for completion of the viral life cycle and vertical transmission to the next generation. to investigate the functional significance of extensive viral superantigen (sag) glycosylation, we disrupted the six potential sites for n-linked carbohydrate addition i ... | 1997 | 9123822 |
| how hormone receptor-dna binding affects nucleosomal dna: the role of symmetry. | molecular dynamics simulations have been employed to determine the optimal conformation of an estrogen receptor dna binding domain dimer bound to a consensus response element, ds(aggtcacagtgacct), and to a nonconsensus response element, ds(agaacacagtgacct). the structures simulated were derived from a crystallographic structure and solvated by a sphere (45-a radius) of explicit water and counterions. long-range electrostatic interactions were accounted for during 100-ps simulations by means of a ... | 1997 | 9129808 |
| t cell deletion induced by chronic infection with mouse mammary tumor virus spares a cd25-positive, il-10-producing t cell population with infectious capacity. | we found that t cells recognizing viral superantigen (vsag) can be subdivided into two distinct functional subsets based on il-2r alpha (cd25) expression. cd4+vbeta6+cd25- and cd4+vbeta6+cd25+ t cells were sensitive to vsag activation. when obtained from balb/c(sw) mice, both subsets were infected and capable to induce the tolerance process when transferred into noninfected recipients. however, in contrast to cd4+vbeta6+cd25- cells, which were gradually deleted in mmtv(sw)-infected mice, the poo ... | 1997 | 9144476 |
| an unlikely link? researchers probe viral role in breast cancer. | | 1997 | 9150180 |
| the mouse mammary tumor associated gene int3 is a unique member of the notch gene family (notch4). | the int3 gene is frequently rearranged in mouse mammary tumor virus (mmtv)-induced mammary tumors of the czechii mouse strain. we have completed the nucleotide sequence of the normal 6.5 kb int3 rna and defined the intron/exon boundaries of the gene. the open reading frame of int3 rna should encode a 200 kd protein which shares 60% homology with the mouse homologue of drosophila notch. int3 is unique among other members of the notch family by containing 29 instead of 36 egf-like repeats in the e ... | 1997 | 9150355 |
| histone acetylation influences thyroid hormone and retinoic acid-mediated gene expression. | thyroid hormone (t3) and retinoic acid (ra) receptors regulate transcription of the rat growth hormone (gh) gene through binding to a common hormone response element (hre) in the promoter. we have investigated the effect of histone acetylation on hormone-dependent expression of the rat gh gene. we examined the effect of butyrate, which induces histone hyperacetylation, and trichostatin a (tsa), a highly specific inhibitor of histone deacetylases. gh-mrna levels were significantly increased in pi ... | 1997 | 9150429 |
| the nasal-associated lymphoid tissue of adult mice acts as an entry site for the mouse mammary tumor retrovirus. | mouse mammary tumor virus (mmtv) is a b type retrovirus transmitted to the suckling offspring through milk. mmtv crosses the intestinal barrier of neonates, initially infects the lymphoid cells of the peyer's patches, and later spreads to all lymphoid organs and to the mammary gland. adult mice can be infected systemically, but not by oral mmtv administration. in this study, we show that nasal administration of infected milk induces the infection of adult mice. nasal mmtv infection shared the ma ... | 1997 | 9151713 |
| genomic structures of viral agents in relation to the biosynthesis of selenoproteins. | the genomes of both bacteria and eukaryotic organisms are known to encode selenoproteins, using the uga codon for seleno-cysteine (sec), and a complex cotranslational mechanism for sec incorporation into polypeptide chains, involving rna stem-loop structures. these common features and similar codon usage strongly suggest that this is an ancient evolutionary development. however, the possibility that some viruses might also encode selenoproteins remained unexplored until recently. based on an ana ... | 1997 | 9152512 |
| possibilities of a viral etiology for human breast cancer. a review. | previous studies related mouse mammary tumor virus (mmtv) to human breast cancer. however, the presence of human endogenous retroviruses (hers) confounded these results. we selected a 660-bp sequence of the mmtv env gene with low homology to her (or any other known gene) and searched for a sequence homologous to it, using the polymerase chain reaction (pcr). the 660-bp sequence was detected in 131 (39%) of 335 unselected breast cancers, in 2 (6.9%) of 29 fibroadenomas, and in 2 (1.65%) of 121 no ... | 1997 | 9152517 |
| neu/erbb2 cooperates with p53-172h during mammary tumorigenesis in transgenic mice. | thirty percent of human breast cancers have amplification of erbb2, often in conjunction with mutations in p53. the most common p53 mutation in human breast cancers is an arg-to-his mutation at codon 175, an allele that functions in a dominant oncogenic manner in tumorigenesis assays and is thus distinct from loss of p53. transgenic mice expressing mouse mammary tumor virus-driven neu transgene (mmtv-neu) develop clonal mammary tumors with a latency of 234 days, suggesting that other events are ... | 1997 | 9154814 |
| mouse mammary tumor virus and the immune system. | | 1997 | 9160112 |
| differential activity of progesterone and glucocorticoid receptors on mouse mammary tumor virus templates differing in chromatin structure. | in vivo, transcription factors interact with promoters having complex nucleoprotein structures. the transiently expressed progesterone receptor (pr) efficiently activates a transfected mouse mammary tumor virus (mmtv) promoter but is a poor activator of the mmtv promoter when it acquires an ordered chromatin structure as an endogenous, replicating gene. we show that the deficiency in pr activity is not due to insufficient expression of either b or a isoforms or competition between the two types ... | 1997 | 9162055 |
| the mtv29 gene encoding endogenous lymphoma superantigen in sjl mice, mapped to proximal chromosome 6. | | 1997 | 9162105 |
| analysis of chromatin structure in vivo. | a number of important nuclear processes including replication, recombination, repair, and transcription involve the interaction of soluble nuclear proteins with dna assembled as chromatin. recent progress in a number of experimental systems has focused attention on the influence chromatin structure may exert on gene regulation in eukaryotes. with the advent of new technologies for the analysis of chromatin structure in vivo, studies evaluating the influence of chromatin structure on gene transcr ... | 1997 | 9169200 |
| crosslinking of progesterone receptor to dna using tuneable nanosecond, picosecond and femtosecond uv laser pulses. | uv laser crosslinking is a potentially powerful tool to investigate transient dna-protein interactions and binding kinetics in intact cells. as the processes underlying uv laser crosslinking are not fully understood, we have performed a study of the influence of laser pulses with different physical parameters on crosslinking of the progesterone receptor to an oligonucleotide containing a hormone-responsive element. we also studied the influence of the various parameters on the amount of laser-ir ... | 1997 | 9171102 |
| glucocorticoid receptor function possibly modulates cell-cell interactions in osteoblastic metastases on rat skeleton. | we analysed the glucocorticoid receptor (gr) function and its ability to modulate cell-cell interactions between the pa-iii rat prostate cancer and umr 106 osteoblast-like rat osteosarcoma cells as an in vitro model for studying gr function in pa-iii cell-induced tumor and blastic reaction in rat bone. intact gr was detected by ligand binding assays, dna band-shift, and gr trans-activation analysis of pa-iii and umr 106 cells transiently transfected with the mouse mammary tumor virus thymidine k ... | 1997 | 9174122 |
| second messengers induced by the envelope protein of a retrovirus. | the envelope protein (gp52) of the mouse mammary tumor virus (mmtv) can stimulate rna synthesis via binding to its cellular receptor on mammary epithelium. this effect was mimicked by either nitric oxide (no) or 8-bromo-cgmp and was blocked by an no inhibitor. furthermore, the effects of gp52 and 8-bromo-cgmp were not additive at maximal concentrations, suggesting that they were using the same signaling route. finally, gp52 elevated cgmp levels in mammary epithelium. these data suggest that gp52 ... | 1997 | 9175626 |
| long-term feeding of field bean protein containing protease inhibitors suppresses virus-induced mammary tumors in mice. | protease inhibitors (pis) of synthetic, bacterial or soybean origin have been shown to suppress carcinogen or radiation-induced rat mammary carcinogenesis. we report, for the first time, the effect of year-long feeding of field bean meal, a rich source of pis with a 24% protein content, at different protein levels in the diet, on mouse mammary tumor virus (mmtv)-induced mammary tumorigenesis in c3h/jax mice. weanling female mice were randomized and divided into groups and fed chow or chow with 2 ... | 1997 | 9177450 |
| effects of melatonin on mammary gland lesions in transgenic mice overexpressing n-ras proto-oncogene. | the oncostatic effects of melatonin on the mammary gland have been studied in transgenic mice carrying the n-ras proto-oncogene under the control of the mmtv-ltr. female (4-week-old) virgin mice with positive transgenic pedigrees were injected with melatonin (200 micrograms/mouse/ day, five times a week) or vehicle late in the evening. after 5 months of treatment, animals were sacrificed and the mammary glands were dissected for whole mounts, histology, and immunohistochemical analysis with a mo ... | 1997 | 9181520 |
| b cell response and histology of a retroviral infection in vivo. | | 1997 | 9186698 |
| the ns1 protein of the autonomous parvovirus minute virus of mice blocks cellular dna replication: a consequence of lesions to the chromatin? | the nonstructural protein ns1 of the autonomous parvovirus minute virus of mice interferes with cell division and can cause cell death, depending on the cell transformation state. upon infection, the synthesis of ns1 protein is massively initiated during s phase. in this article, we show that minute virus of mice-infected cells accumulate in this phase. to investigate the link between ns1 accumulation and s-phase arrest, we have used stably transfected cells in which ns1 expression is under the ... | 1997 | 9188601 |
| proto-oncogene of int-3, a mouse notch homologue, is expressed in endothelial cells during early embryogenesis. | notch and its homologues are key regulatory receptors of the cell fate decision in various developmental processes. the int-3 oncogene was originally identified as a frequent target in mouse mammary tumour virus (mmtv)-induced mammary tumours and has been regarded as a notch homologue, based on its similarity to the intracellular domain of notch. studies with int-3 transgenic mice have suggested that the int-3 transgene affects the differentiation capacity of stem cells and leads to neoplastic p ... | 1997 | 9189758 |
| transgenic monocyte chemoattractant protein-1 (mcp-1) in pancreatic islets produces monocyte-rich insulitis without diabetes: abrogation by a second transgene expressing systemic mcp-1. | monocyte chemoattractant protein-1 (mcp-1) is a cc chemokine that attracts monocytes and t lymphocytes in vitro; however, its in vivo functions are poorly understood. to address this question, we constructed transgenic mice expressing mcp-1 controlled by an insulin promoter. these mice developed a chronic insulitic infiltrate composed of f4/80+ monocytes with minor populations of cd4+, cd8+, and b220+ cells. despite persistent transgene expression, the insulitis never progressed, and blood gluco ... | 1997 | 9200479 |
| fibroblast growth factor receptor signalling has a role in lobuloalveolar development of the mammary gland. | we have used the mouse mammary tumor virus promoter to express two dominant negative (dn) fibroblast growth factor receptor (fgfr) isoforms in the mammary epithelium of transgenic mice. while expression of dn-fgfr1(iiic) showed no discernible phenotype, a similar kinase negative form of fgfr2(iiib) caused a marked impairment of lobuloalveolar development. the growth retardation was apparent by mid-pregnancy and persisted in the post-partum glands. despite the substantial underdevelopment of the ... | 1997 | 9202386 |
| prolactin, epidermal growth factor or transforming growth factor-alpha activate a mammary cell-specific enhancer in mouse mammary tumor virus-long terminal repeat. | mammary specific expression of elevated levels of mouse mammary tumor virus (mmtv) contributes to mammary carcinogenesis. mechanisms which regulate provirus expression have not been completely defined. using a mmtv-long repeat terminal (mmtv-lrt) directed chloramphenicol-acetyltransferase (cat) reporter gene system and a human breast cancer cell line t47d, we demonstrate that prolactin (prl), epidermal growth factor (egf), or transforming growth factor-alpha (tgf-alpha) act on a mammary cell-spe ... | 1997 | 9202398 |
| preferential activation of fgf8 by proviral insertion in mammary tumors of wnt1 transgenic mice. | mouse mammary tumor virus (mmtv) is an insertional mutagen that has been demonstrated to transcriptionally activate flanking cellular proto-oncogenes. previously we have used mmtv infection to accelerate mammary tumorigenesis in wnt1 transgenic mice in order to identify genes that cooperate with the wnt1 oncogene. initial investigations into the resulting tumor collection, screened primarily by southern analysis, showed that three fibroblast growth factor genes, fgf8, fgf3 and fgf4, sustain acti ... | 1997 | 9205106 |
| plasmodium yoelii: resistance to disease is linked to the mtv-7 locus in balb/c mice. | we have identified congenic mouse strains that differ dramatically in resistance to infection with the murine malaria parasite plasmodium yoelii 17x. after infection, balb/c mice develop severe anemia and a high degree of parasitemia which sometimes results in death. the mtv-7 congenic strain balb.d2.mlsa, however, develops only a mild degree of anemia and parasitemia. in this paper we describe the course of the disease and discuss the potential role of mtv-7 and linked loci in control of this i ... | 1997 | 9207740 |
| mouse mammary tumor virus: a virus that exploits the immune system. | mouse mammary tumor virus (mmtv) causes mammary carcinomas and t-cell tumors in mice. mmtv variants that induce t-cell tumors have a large deletion within the u3 region of the long terminal repeat (ltr) compared to mmtv strains that induce mammary tumors. we provide evidence here that t-cell tropic mmtv strains lack a redundant binding site for a cellular protein called nbp (negative regulatory element binding protein). the lack of nbp-binding sites in t-cell tropic mmtv strains presumably leads ... | 1997 | 9209337 |
| differential hormone-dependent transcriptional activation and -repression by naturally occurring human glucocorticoid receptor variants. | the molecular mechanisms underlying primary glucocorticoid resistance or hypersensitivity are not well understood. using transfected cos-1 cells as a model system, we studied gene regulation by naturally occurring mutants of the glucocorticoid receptor (gr) with single-point mutations in the regions encoding the ligand-binding domain or the n-terminal domain reflecting different phenotypic expression. we analyzed the capacity of these gr variants to regulate transcription from different promoter ... | 1997 | 9212062 |
| expression of transgenic carcinoembryonic antigen (cea) in tumor-prone mice: an animal model for cea-directed tumor immunotherapy. | carcinoembryonic antigen (cea) is a tumor marker for the most common forms of adenocarcinomas. we have previously described c57bl/6 mice transgenic for the complete human cea gene. compared with humans, these mice reveal a conserved spatiotemporal cea expression pattern. to establish animal models for cea-targeted tumor immunotherapy, we have crossed cea transgenic mice with mice that are genetically predisposed to tumor development. these immunocompetent animals should allow optimization of imm ... | 1997 | 9212243 |
| the hepatitis b virus x gene induces p53-mediated programmed cell death. | the human hepatitis b virus (hbv) protein px is a multifunctional regulatory protein that is known to affect both transcription and cell growth. here we describe induction of apoptosis in nih 3t3 polyclonal cell lines upon stimulation of px expression from a dexamethasone inducible mouse mammary tumor virus (mmtv)-x expression vector. the effect of long-term px expression on the cell survival of mouse fibroblasts was confirmed in colony generation assays. this effect is not shared either by the ... | 1997 | 9223332 |
| both t and b cells shed infectious mouse mammary tumor virus. | mouse mammary tumor virus (mmtv) infected both b and t tissue culture cells and primary b and t cells in vivo after milk-borne transmission of the virus. the infected tissue culture cells processed viral proteins, and both these and primary b and t cells shed virus when cultured in vitro. moreover, the infected b and t tissue culture cells transmitted virus to uninfected mammary gland cells in vitro. the level of infection of these different cell types in vivo was dependent on the strain of mous ... | 1997 | 9223496 |
| evidence for immune facilitation of breast cancer growth and for the immune promotion of oncogenesis in breast cancer. | autoimmune diseases have been extensively studied in man and experimental animal models and salient points are reviewed, as a clear understanding of the immune mechanisms involved is essential if one is to understand the potential of immune interactions with established cancer cells or in the premalignant period of hyperplasia. such reactions may be of benefit to the host, with down regulation of tumor growth, or unfavourable, with facilitation of oncogenesis and cancer growth. in particular, ev ... | 1996 | 9224971 |
| mouse mammary tumor virus/v-ha-ras transgene-induced mammary tumors exhibit strain-specific allelic loss on mouse chromosome 4. | hybrid mice carrying oncogenic transgenes afford powerful systems for investigating loss of heterozygosity (loh) in tumors. here, we apply this approach to a neoplasm of key importance in human medicine: mammary carcinoma. we performed a whole genome search for loh using the mouse mammary tumor virus/v-ha-ras mammary carcinoma model in female (fvb/n x mus musculus castaneus)f1 mice. mammary tumors developed as expected, as well as a few tumors of a second type (uterine leiomyosarcoma) not previo ... | 1997 | 9238034 |
| a classic camp responsive element in the promoter region of the alpha 1-gabaa receptor subunit has non-classic properties. | the camp responsive element binding protein (creb) and the glucocorticoid receptor (gr) have been reported to bind to a 60 bp promoter fragment of the alpha 1-gabaa receptor gene containing a classic camp-responsive element (cre). we inserted this fragment into a hormone responsive element-deleted mouse mammary tumor virus promoter controlling the expression of luciferase. activation of gr showed no significant change in luciferase expression, but hormone induction by forskolin revealed a reduct ... | 1997 | 9238338 |
| mouse mammary tumor virus: immunological interplays between virus and host. | | 1997 | 9238510 |
| a human endogenous retroviral superantigen as candidate autoimmune gene in type i diabetes. | microbial superantigens (sags) have been implicated in the pathogenesis of human autoimmune diseases. preferential expansion of the vveta7 t cell receptor positive t cell subset in patients suffering from acute-onset type i diabetes has indicated the presence of a surface membrane-bound sag. here, we have isolated a novel mouse mammary tumor virus-related human endogenous retrovirus. we further show that the n-terminal moiety of the envelope gene encodes an mhc class ii-dependent sag. we propose ... | 1997 | 9244304 |
| variant mouse lymphoma cells with modified response to interferon demonstrate enhanced immunogenicity. | we have previously developed an experimental model for the xenogenization of malignant lymphoma. from highly tumorigenic s49 mouse lymphoma cells that proliferate in suspension culture (designated t-25), we selected variant clones that grew as an adherent monolayer (designated t-25-adh) and were non-tumorigenic in syngeneic mice. furthermore, priming of syngeneic hosts with t-25-adh cells protected them against subsequent challenges with the tumorigenic t-25 cells. several lines of evidence have ... | 1997 | 9247559 |
| purkinje cell protein-2 cis-elements mediate repression of t3-dependent transcriptional activation. | previous studies in our laboratory show that triiodothyronine upregulates expression of the cerebellar purkinje cell-specific gene pcp-2 during the first 2 weeks of rat neonatal life. a specific thyroid hormone response element, the a1 tre, mediates this regulation. the finding that the contiguous 68 bases (-267/ -199) of the pcp-2 promoter 3' to the a1 tre repressed t3 response in transactivation studies suggested that this sequence could play a role in preventing premature t3-dependent activat ... | 1997 | 9256366 |
| histopathological features of the harderian glands in transgenic mice carrying mmtv/n-ras protooncogene. | the harderian gland is a tubule-alveolar gland found within the orbit, on the posterior aspect of the eyeball. in mice, it is composed almost exclusively of secretory tubules and alveoli. the harderian glands of transgenic mice, carrying the activated n-ras oncogene under the transcriptional control of the mouse mammary tumor virus long terminal repeat promoter (mmtv-ltr), were examined and compared to those of normal mice. thirty transgenic mice provided by a. pellicer (nyu) and 30 normal mice ... | 1997 | 9264342 |
| immunization with a mouse mammary tumour virus envelope protein epitope protects against tumour formation without inhibition of the virus infection. | balb/c mice were immunized with the ep3 surface epitope of the mouse mammary tumour virus (mmtv) gp52 envelope protein before systemic infection with mmtv(c3h) or mmtv(sw). analysis of the successive stages of the virus infection showed that although these mice were protected against mammary tumour formation, earlier stages of the infection were not inhibited, as reflected by the persisting superantigen-induced activation and deletion of vbeta-specific t cells. transplacental transfer of materna ... | 1997 | 9266991 |
| specific deactivation of the mouse mammary tumor virus long terminal repeat promoter upon continuous hormone treatment. | we have studied the transcriptional behavior of the mouse mammary tumor virus long repeat (mmtv-ltr) promoter during a prolonged exposure to glucocorticoids. when integrated into xc-derived cells, mmtv-ltr expression reached its maximum during the first day of dexamethasone treatment, but longer exposure to the hormone resulted in the deactivation of the promoter. in contrast, glucocorticoid-responsive resident genes or mmtv-based transiently transfected plasmids maintained or even increased the ... | 1997 | 9268310 |
| loss of heterozygosity analysis in primary mammary tumors and lung metastases of mmtv-mtag and mmtv-neu transgenic mice. | loss of heterozygosity (loh) analysis has been used in many types of human cancer to localize putative tumor suppressor genes important in carcinogenesis. however, this approach has only recently been applied to transgenic mouse tumor models, which offer greater opportunity for detailed molecular genetic analysis of tumor initiation and progression. to explore the possible role of secondary genetic events in transgenic mouse mammary tumor development, we performed microsatellite-based allelotype ... | 1997 | 9270023 |
| the matrix attachment region-binding protein satb1 participates in negative regulation of tissue-specific gene expression. | the nuclear matrix has been implicated in several cellular processes, including dna replication, transcription, and rna processing. in particular, transcriptional regulation is believed to be accomplished by binding of chromatin loops to the nuclear matrix and by the concentration of specific transcription factors near these matrix attachment regions (mars). a number of mar-binding proteins have been identified, but few have been directly linked to tissue-specific transcription. recently, we hav ... | 1997 | 9271405 |
| t cells bearing vbeta8 are preferentially infected with exogenous mouse mammary tumor virus. | we previously reported that a mouse mammary tumor virus (mmtv(ii-tes14)), encoding a superantigen specific for tcr vbeta14, can infect lymph node (ln) cells of mice in an i-e-independent manner. here we examined the kinetics of cell types infected with exogenous mmtv in the draining ln after s.c. injection of ii-tes milk containing mmtv(ii-tes14). the infectivity was assessed in ln cells sorted into each cell subset by a semiquantitative analysis of mmtv provirus using pcr with a primer specific ... | 1997 | 9278306 |
| binding of nf1 to the mmtv promoter in nucleosomes: influence of rotational phasing, translational positioning and histone h1. | to analyse the role of rotational orientation and translational positioning of nucleosomal dna on transcription factor binding we have generated a series of mutant mmtv promoters containing insertions of various lengths between the hormone-responsive region and the binding site for nf1. these various mmtv promoter fragments were assembled in mononucleosomes and used for structural studies and binding experiments. we show that the insertions change the rotational phase and translational positioni ... | 1997 | 9278498 |
| in vitro negative selection of viral superantigen-reactive thymocytes by thymic dendritic cells. | intrathymic expression of endogenous mouse mammary tumor virus (mmtv)-encoded superantigens (sag) induces the clonal deletion of t cells bearing sag-reactive t-cell receptor (tcr) vbeta elements. however, the identity of the thymic antigen-presenting cells (apc) involved in the induction of sag tolerance remains to be defined. we have analyzed the potential of dendritic cells (dc) to mediate the clonal deletion of mtv-7-reactive tcr alphabeta p14 transgenic thymocytes in an in vitro assay. our r ... | 1997 | 9292528 |
| t cell repertoire formation displays characteristics of qualitative models of thymic selection. | the use of t cell receptor elements varies between mouse strains, reflecting a balance between positive and negative selection. the presence of h-2e biases v alpha and v beta usage through major histocompatibility class ii isotype preferences of v elements, and mammary tumor virus-dependent, negative selection. quantitative models of thymic selection predict that negative selection equates to 'excess' positive selection, whereas qualitative models suggest that positive and negative selection are ... | 1997 | 9295014 |
| the translation initiation factor eif3-p48 subunit is encoded by int-6, a site of frequent integration by the mouse mammary tumor virus genome. | translation initiation factor eif3 is a large, multisubunit protein complex that plays a central role in the pathway of initiation by promoting the binding of both methionyl-trnai and mrna to the 40s ribosomal subunit. as part of a broad effort to elucidate the structure of eif3, we have cloned and sequenced the human cdna encoding the 48-kda subunit, eif3-p48. the recombinant protein comigrates with the authentic p48 subunit in purified eif3 and coprecipitates with affinity-purified antibodies ... | 1997 | 9295280 |
| strain-specific expression of spliced mmtv rnas containing the superantigen gene. | the transmission of milk-borne or exogenous mouse mammary tumor virus (mmtv) requires infection of b cells in the gut-associated lymphoid tissue and expression of the superantigen (sag) protein at the b-cell surface. presentation of sag at the b-cell surface is required for the transmission of mmtv to t cells and subsequent infection of the target mammary gland tissue. because several different promoters have been reported for mmtv sag mrna expression, we investigated whether the detection of sp ... | 1997 | 9299617 |
| early neutralizing antibody response against mouse mammary tumor virus: critical role of viral infection and superantigen-reactive t cells. | infectious mouse mammary tumor virus (mmtv) is a retrovirus that expresses a superantigen shortly after infection of b cells. the superantigen first drives the polyclonal activation and proliferation of superantigen-reactive cd4+ t cells, which then induce the infected b cells to proliferate and differentiate. part of the mmtv-induced b cell response leads to the production of abs that are specific for the viral envelope protein gp52. here we show that this ab response has virus-neutralizing act ... | 1997 | 9300703 |
| a novel in vitro and in vivo breast cancer model for testing inhibitors of estrogen biosynthesis and its action using mammary tumor cells with an activated int-5/aromatase gene. | we recently showed that the cellular gene int-5/aromatase in balb/c mammary alveolar hyperplastic nodule (d2 han/d2 tumor cells) is activated as a result of mouse mammary tumor virus integration within the 3' untranslated region of the aromatase gene. in the present study, we evaluated the effect of various aromatase inhibitors on androstenedione-mediated tumor cell growth. also, we compared the effect of the non-steroidal aromatase inhibitor (cgs 16949a) on the inhibition of tumor growth. our r ... | 1997 | 9310256 |
| a highly sensitive in vitro infection assay to explore early stages of mouse mammary tumor virus infection. | mouse mammary tumor virus (mmtv) infection of adult mice induces a strong response to superantigen (sag) in their draining lymph nodes, which results from the presentation of sag by mmtv-infected b cells to sag-reactive t cells. to date, infection with physiologically relevant doses of mmtv can be detected in vivo only after several days of sag-mediated t-cell-dependent amplification of infected b cells. furthermore, no efficient in vitro system of detecting mmtv infection is available. such a m ... | 1997 | 9311804 |
| retrovirus-induced target cell activation in the early phases of infection: the mouse mammary tumor virus model. | mouse mammary tumor virus (mmtv) infects b lymphocytes and expresses a superantigen on the cell surface after integration of its reverse-transcribed genome. superantigen-dependent b- and t-cell activation becomes detectable 2 to 3 days after infection. we show here that before this event, b cells undergo a polyclonal activation which does not involve massive proliferation. this first phase of b-cell activation is t cell independent. moreover, during the first phase of activation, when only a sma ... | 1997 | 9311805 |
| role of mmtv integration locus cellular genes in breast cancer. | mouse mammary tumorigenesis as a result of mouse mammary tumor virus (mmtv) integrations has helped to identify a wide variety of interesting genes that play a role in mammary development and tumorigenesis. several such genes int1/wnt1, wnt3, wnt 10b, int2/fgf3, fgf4, int3/notch and int6 have been shown to be genetically altered in naturally formed mammary tumors as a consequence of mmtv integration. some of these genes have been well characterised and examined in in vivo breast cancer transgeni ... | 1997 | 9334290 |
| cre-mediated gene deletion in the mammary gland. | to delete genes specifically from mammary tissue using the cre-lox system, we have established transgenic mice expressing cre recombinase under control of the wap gene promoter and the mmtv ltr. cre activity in these mice was evaluated by three criteria. first, the tissue distribution of cre mrna was analyzed. second, an adenovirus carrying a reporter gene was used to determine expression at the level of single cells. third, tissue specificity of cre activity was determined in a mouse strain car ... | 1997 | 9336464 |
| massive mammary gland infection and pregnancy-dependent mammary tumor development in mice infected neonatally with mouse mammary tumor virus (sw) but not in mice infected as adults, despite a dramatic local response. | mouse mammary tumor virus (mmtv) (sw) caused a high incidence (65%) of pregnancy-dependent adenocarcinomas in balb/c(sw) mice infected as newborns by suckling their mothers' milk. these tumors were type b adenocarcinomas which developed early, at about 1 year of age. uninfected breeding females and those infected at an age of 8 weeks by injection of virus had the same low incidence of malignant tumors (13%), and the tumors developed later (at approx. 23-24 months). the low incidence of tumors in ... | 1997 | 9341752 |