| mammary tumor suppression by transforming growth factor beta 1 transgene expression. | in cell culture, type alpha transforming growth factor (tgf-alpha) stimulates epithelial cell growth, whereas tgf-beta 1 overrides this stimulatory effect and is growth inhibitory. transgenic mice that overexpress tgf-alpha under control of the mouse mammary tumor virus (mmtv) promoter/enhancer exhibit mammary ductal hyperplasia and stochastic development of mammary carcinomas, a process that can be accelerated by administration of the chemical carcinogen 7,12-dimethylbenz[a]anthracene. mmtv-tgf ... | 1995 | 7753792 |
| dual transcriptional control by ear3/coup: negative regulation through the dr1 direct repeat and positive regulation through a sequence downstream of the transcriptional start site of the mouse mammary tumor virus promoter. | ear3/coup is an orphan member of the steroid/thyroid hormone receptor superfamily of transcription factors and binds most tightly to a direct repeat of aggtca with 1 nucleotide in between (dr1). ear3/coup also binds with a similar affinity to the palindromic thyroid hormone response element (tre). this binding preference of ear3/coup is same as that of the retinoid x receptor (rxr), which is another member of the superfamily. in the present study, we identified a sequence responsible for ear3/co ... | 1995 | 7753823 |
| a macrocircular ellagitannin, oenothein b, suppresses mouse mammary tumor gene expression via inhibition of poly(adp-ribose) glycohydrolase. | oenothein b, a macrocircular dimeric ellagitannin, was found to be a potent and specific inhibitor of poly(adp-ribose) glycohydrolase. oenothein b suppressed glucocorticoid-sensitive mouse mammary tumor virus (mmtv) transcription in 34i cells. this suppression was accompanied by inhibition of glucocorticoid-induced endogeneous de-poly(adp-ribosyl)ation of high mobility group (hmg) 14 and 17 proteins. these results suggest that de-poly(adp-ribosyl)ation of these proteins may be closely connected ... | 1995 | 7755607 |
| multiple metastases of mammary carcinoma cell lines isolated from feral mouse. | two established cell lines (jyg-a and b) isolated from mammary carcinoma tissues of m. m. musculus sub-jyg (a chinese wild mouse) showed multiple metastasis in the lung (100%), liver (40-60%), kidney (40-80%), lymph node (20-60%) and other organs of the nude mice inoculated with these cells subcutaneously or intravenously. in addition, 100% brain metastasis or infiltration was observed only when inoculated with jyg-b cells intravenously. | 1995 | 7757963 |
| concomitant infection with exogenous mouse mammary tumor virus encoding i-e-dependent superantigen in i-e-negative mouse strain. | we found that milk from ii tes mice contained two species of exogenous mouse mammary tumor viruses (mmtv). sequence analysis of the open reading frame (orf) in the mmtv 3' long terminal repeat indicated that the two mmtv, mmtv (ii tes2) and mmtv (ii tes14), encode superantigens specific for v beta 2+ t cells and v beta 14+ t cells, respectively. in an experiment of subcutaneous injection of ii tes milk, both t cells bearing tcr v beta 2 and v beta 14 proliferated vigorously in the draining lymph ... | 1995 | 7759859 |
| c-fos is a positive regulator of carcinogen enhancement of adenovirus transformation. | the early gene expression changes mediating carcinogen enhancement of viral transformation (cet) remain to be elucidated. a model cell culture system has been developed that is now permitting a molecular analysis of cet. pretreatment of cloned rat embryo fibroblast (cref) cells with methyl methanesulfonate (mms) prior to infection with the cold-sensitive host-range type 5 adenovirus mutant, h5hr1, results in a dose-dependent increase in viral transformation. the present study investigates the ro ... | 1995 | 7761104 |
| mouse mammary tumor viruses with functional superantigen genes are selected during in vivo infection. | mouse mammary tumor virus (mmtv) encodes a superantigen that is important for viral infectivity in vivo. to determine whether superantigen function was required for infection by milk-borne mmtv, we created hyb pro/cla transgenic mice. these mice produced a full-length, packaged viral rna with a frameshift mutation that caused premature termination of the superantigen protein. young hyb pro/cla mice showed no deletion of their cognate v beta 14+ t cells, although they shed virus in their milk. th ... | 1995 | 7761408 |
| expression of antisense osteopontin rna inhibits tumor promoter-induced neoplastic transformation of mouse jb6 epidermal cells. | elevated expression of osteopontin (opn), a secreted adhesive phosphoglycoprotein, is frequently associated with many transformed cell lines of epithelial and stromal origin. moreover, several clonal lines of preneoplastic jb6 cells derived from balb/c mouse epidermal cultures (colburn et al., 1978, 1979), upon treatment with 12-o-tetradecanoyl phorbol-13-acetate (tpa), become irreversibly oncogenic and concomitantly synthesize opn at elevated levels (smith and denhardt, 1989). in the present st ... | 1995 | 7784060 |
| in vivo binding of proteins to stably integrated mmtv dna in murine cell lines: occupancy of nfi and otf1 binding sites in the absence and presence of glucocorticoids. | activation of expression at the mouse mammary tumor virus (mmtv) promoter is thought to be controlled by nucleosome positioning. on stably integrated mmtv dna, the long terminal repeat (ltr) region is organized in a phased array of nucleosomes which allegedly occludes transcription factors such as nfi from binding. nfi only binds to the promoter region when the ordered nucleosome structure is apparently disrupted by activated steroid hormone receptors in hormone induced transcription. in certain ... | 1994 | 7787882 |
| quantitative differences in androgen and glucocorticoid receptor dna binding properties contribute to receptor-selective transcriptional regulation. | androgen receptor (ar) and glucocorticoid receptor (gr) belong to the same subfamily of steroid/nuclear receptors and have been shown to bind qualitatively to the same hormone response element (hre) dna sequences. despite this similarity in target gene recognition, ar and gr have differential affects on the transcriptional regulation of genes containing both simple and complex hre control regions. using hres from the mouse mammary tumor virus (mmtv), tyrosine aminotransferase (tat), prostatein ( ... | 1995 | 7789609 |
| the role of superantigens in the immunobiology of retroviruses. | murine mammary tumour viruses (mmtvs) are retroviruses that encode superantigens capable of stimulating t cells via superantigen-reactive t cell receptor v beta chains. mmtvs are transmitted to the suckling offspring via the milk. we have established that class ii and b cell-deficient mice that were foster nursed by virus-secreting mice do not transfer infectious mmtvs to their offspring. no mmtv proviruses could be detected in the spleen and mammary tissue of these mice and there was no deletio ... | 1994 | 7796668 |
| dissection of progesterone receptor-mediated chromatin remodeling and transcriptional activation in vivo. | we have investigated whether constitutive binding by the progesterone receptor (pr) to a promoter is required for the maintenance of an open chromatin structure in vivo. for these experiments, we used human t47d breast cancer cells in which the mouse mammary tumor virus (mmtv) promoter, stably assembled as chromatin, is constitutively hypersensitive to endonucleolytic cleavage. in vivo footprinting revealed that transcription factors nuclear factor 1 and the pr were constitutively bound to the m ... | 1995 | 7797076 |
| cloning, bacterial expression, and characterization of the mason-pfizer monkey virus proteinase. | we have cloned and expressed the 3' region of the mason-pfizer monkey virus pro gene in escherichia coli. the recombinant 26-kda precursor undergoes rapid self-processing both in e. coli and in vitro at the nh2 terminus, yielding a proteolytically active 17-kda protein, p17. this initial cleavage is followed in vitro by a much slower self-processing that leads to emergence of proteolytically active p12 and a cooh-terminal cleavage product p5. we have found the nh2-terminal processing site of bot ... | 1995 | 7797487 |
| regulation of neurite outgrowth and snap-25 gene expression by the brn-3a transcription factor. | snap-25 is a presynaptic nerve terminal protein which is also essential for the process of neurite outgrowth in vivo and in vitro. however the processes regulating its expression have not been characterized previously. we show that the gene encoding this protein, snap, is strongly activated by the brn-3a pou (pit-oct-unc) family transcription factor. expression of both brn-3a and snap-25 increases when nd7 neuronal cells are induced to extend neurite processes by serum removal. inhibition of brn ... | 1995 | 7797590 |
| mouse mammary tumor virus chromatin in human breast cancer cells is constitutively hypersensitive and exhibits steroid hormone-independent loading of transcription factors in vivo. | we have stably introduced a reporter gene under the control of the mouse mammary tumor virus (mmtv) long terminal repeat (ltr) into human t47d breast cancer cells to study the action of the progesterone receptor (pr) on transcription from a chromatin template. unexpectedly, the chromatin organization of the mmtv ltr in these human breast cancer cells differed markedly from what we have observed previously. the region adjacent to the transcription start site (-221 to -75) was found to be constitu ... | 1995 | 7799933 |
| alteration of phosphoinositide metabolism by attenuation of camp resulting from expression of the h-ras oncogene. | most studies characterizing h-ras have been conducted in constitutively expressing cell lines. to explore the early interaction between h-ras p21 and signal transduction systems we have utilized an nih3t3 fibroblast line transfected with a steroid inducible mmtv h-ras vector. exposure to dexamethasone resulted in transcription of h-ras accompanied by an increase in pi turnover. addition of camp analogs restored pi metabolism to control level. we postulate that these effects are due to the regula ... | 1994 | 7802640 |
| normal and neoplastic mammary gland growth in mmtv/tgf alpha transgenic mice. | biochemical and dynamic change of mammary glands in different reproductive states were studied in comparison with histological structures in female and male transgenic mice bearing human transforming growth factor alpha (tgf alpha) cdna under the control of the mouse mammary tumour virus enhancer/promoter. female and male f1 mice between shn female and transgenic male mice were divided into tgf alpha (+) and tgf alpha (-) groups according to the presence of tgf alpha gene at approximately 50 day ... | 1994 | 7803702 |
| deletion of cd4+ t cells and thymocytes by apoptosis in mouse mammary tumor virus (c4)-infected v beta 2 transgenic mice. | mouse mammary tumor virus mmtv (c4) encodes a v beta 2-specific superantigen. in v beta 2 transgenic (tg2) mice more than 98% of peripheral t cells express v beta 2. infection of tg2 mice with mmtv (c4) at birth through their mothers' milk or at 6-8 weeks of age by intravenous injection resulted in massive deletion of peripheral cd4+ t cells and suppressed thymopoiesis. the number of peripheral cd8+ t cells was not affected in neonatally infected mice. in older mice injected with mmtv (c4), sple ... | 1994 | 7805721 |
| a novel exogenous mammary tumor virus encoding mhc class ii h2e-independent superantigen specific for tcr-v beta 14. | | 1995 | 7806290 |
| negative effects of wild-type p53 and s-myc on cellular growth and tumorigenicity of glioma cells. implication of the tumor suppressor genes for gene therapy. | human (u251, u87, u343) and rat glioma cell lines (c6, 9l) were examined by the reverse transcriptase-polymerase chain reaction and subsequent nucleotide sequencing analysis to see whether they express wild type (wt)-p53 or mutated form (mut)-p53 messages. results showed that u87, u343, and c6 cells expressed wt-p53 messages whereas u251 and 9l cells expressed mut-p53 messages. all these cell lines were transfected with wt-p53 cdna or the s-myc gene linked to the mouse mammary tumor virus (mmtv) ... | 1994 | 7807177 |
| the nature and expression of int-5, a novel mmtv integration locus gene in carcinogen-induced mammary tumors. | our previous studies have resulted in the identification and cloning of int-5, a novel site of mouse mammary tumor virus (mmtv) integration, from balb/c d2 precancerous hyperplastic alveolar nodules (han). this paper presents a detailed characterization of the int-5 locus from both d2 han and normal genome and expression of the unique gene from the mmtv integration site. our results show that the cellular gene at the mmtv integration site in the int-5 locus is identical to the gene encoding arom ... | 1994 | 7812938 |
| response of the phosphoenolpyruvate carboxykinase gene to glucocorticoids depends on the integrity of the camp pathway. | the phosphoenolpyruvate carboxykinase (pepck) gene is regulated at the transcriptional level by a variety of effectors in a tissue-specific fashion. in order to study the parameters involved in the tissue-specific hormonal regulation of the pepck gene, we have used a transient expression test in well-differentiated rat hepatoma cells as well as in dedifferentiated variants. in this test, the pepck promoter is induced by glucocorticoids in well-differentiated fgc4 cells, but not in h5 dedifferent ... | 1994 | 7819133 |
| mhc class ii hierarchy of superantigen presentation predicts efficiency of infection with mouse mammary tumor virus. | superantigens (sags) encoded by infectious mouse mammary tumor viruses (mmtvs) play a crucial role in the viral life cycle. their expression by infected b cells induces a proliferative immune response by sag-reactive t cells which amplifies mmtv infection. this response most likely ensures stable mmtv infection and transmission to the mammary gland. since t cell reactivity to sags from endogenous mtv loci depends on mhc class ii molecules expressed by b cells, we have determined the ability of m ... | 1994 | 7819149 |
| expression of e6/e7 or sv40 large t antigen-coding oncogenes in human corneal endothelial cells indicates regulated high-proliferative capacity. | human corneal endothelial cells are thought to have limited capacity for proliferation. little is known about the mechanisms that regulate the proliferation of these cells. the authors introduced oncogenes into human corneal endothelial cells to modulate proliferation. in addition, they sought to establish cell lines to facilitate study of human corneal endothelial cells. | 1995 | 7822156 |
| hormone-independent repression of ap-1-inducible collagenase promoter activity by glucocorticoid receptors. | the role of the ligand in glucocorticoid receptor-mediated transactivation and transrepression of gene expression was investigated. half-maximal transactivation of a mouse mammary tumor virus-chloramphenicol acetyltransferase reporter gene in transfected cells expressing the human glucocorticoid receptor mutant grl753f, from which the rate of ligand dissociation is four to five times higher than the rate of dissociation from normal receptors, required a 200- to 300-fold-higher concentration of d ... | 1995 | 7823916 |
| structure and biological activity of the subgenomic mtv-6 endogenous provirus. | the mtv-6 provirus has an incomplete genome, but retains a functional superantigen gene (sag) which directs the thymic deletion of cd4+ t cells expressing t cell receptors containing the v beta 3 or v beta 5 chains. to better understand the mtv-6 superantigen, the structure and biological activity of the mtv-6 provirus was analyzed. first, the complete nucleotide sequence was determined, and the mutation producing the subgenomic provirus was identified. second, the nucleotide sequence of the 5' ... | 1995 | 7831795 |
| three genes in the human mhc class iii region near the junction with the class ii: gene for receptor of advanced glycosylation end products, pbx2 homeobox gene and a notch homolog, human counterpart of mouse mammary tumor gene int-3. | cosmid walking of about 250 kb from mhc class iii gene cyp21 to class ii was conducted. the gene for receptor of advanced glycosylation end products of proteins (rage, a member of immunoglobulin superfamily molecules), the pbx2 homeobox gene designated hox12, and the human counterpart of the mouse mammary tumor gene int-3 were found. the contiguous rage and hox12 genes were completely sequenced, and the human int-3 counterpart was partially sequenced and assigned to a notch homolog. this human n ... | 1994 | 7835890 |
| dramatic hyperplasia of mtv-2+ lymph node grafts in mtv-2- recipients and selective stimulation of v beta 14+ t cells in recipients' lymph nodes in the ddd mouse. | ddd/1 (ddd) mice contrast strikingly with ddd-mtv-2/mtv-2 (ddd-mtv-2) congenics in their marked lymph node (ln) t cell paucity. to clarify the possible difference in ln function between them, reciprocal ln grafting experiments were conducted. ddd-mtv-2 ln grafts in ddd recipients underwent hyperplasia as dramatic as 10-to 20-fold increase in weight between 3 and 4 wk after implantation. lymphoid cells in hyperplastic ln grafts were of recipient origin. similar hyperplasia of mtv-2-heterozygous l ... | 1995 | 7836749 |
| the differential capacity of glucocorticoids and progestins to alter chromatin structure and induce gene expression in human breast cancer cells. | the t47d (a1-2) cell line is a human mammary carcinoma-derived cell line that has been engineered to constitutively express comparable levels of both glucocorticoid and progesterone receptors. in addition, these cells possess a stably integrated mouse mammary tumor virus (mmtv) luciferase reporter gene. because the mmtv promoter is recognized similarly by both receptors, we have used this cell line to examine the transcriptional regulatory mechanisms employed by the two receptors. the stably int ... | 1994 | 7838148 |
| 'liver-type' 11 beta-hydroxysteroid dehydrogenase cdna encodes reductase but not dehydrogenase activity in intact mammalian cos-7 cells. | 11 beta-hydroxysteroid dehydrogenase (11 beta-hsd) catalyses the metabolism of corticosterone to inert 11-dehydrocorticosterone, thus preventing glucocorticoid access to otherwise non-selective renal mineralocorticoid receptors (mrs), producing aldosterone selectivity in vivo. at least two isoforms of 11 beta-hsd exist. one isoform (11 beta-hsd1) has been purified from rat liver and an encoding cdna cloned from a rat liver library. transfection of rat 11 beta-hsd1 cdna into amphibian cells with ... | 1994 | 7848528 |
| int-6, a highly conserved, widely expressed gene, is mutated by mouse mammary tumor virus in mammary preneoplasia. | with a unique mouse mammary tumor model system in which mouse mammary tumor virus (mmtv) insertional mutations can be detected during progression from preneoplasia to frank malignancy, including metastasis, we have discovered a new common integration site (designated int-6) for mmtv in mouse mammary tumors. mmtv was integrated into int-6 in a mammary hyperplastic outgrowth line, its tumors and metastases, and two independent mammary tumors arising in unrelated mice. the int-6 gene is ubiquitousl ... | 1995 | 7853537 |
| a third transactivation function (af3) of human progesterone receptors located in the unique n-terminal segment of the b-isoform. | human progesterone target tissues contain two progesterone receptors: b-receptors (hprb), which are 933 amino acids in length, and a-receptors (hpra), which lack the n-terminal 164 amino acids. the two isoforms differ functionally when they are occupied by agonists or antagonists. we postulated that the unique 164-amino acid, b-upstream segment (bus) is in part responsible for the functional differences between the two isoforms and have constructed a series of hpr expression vectors encoding bus ... | 1994 | 7854352 |
| thymic repertoire selection by superantigens: presentation by human and mouse mhc molecules. | the initial report of t cell receptor (tcr) v beta-specific thymic selection in mice showed association with expression of h-2e molecules and affected v beta 17a t cells which were present in cd4+8+ double positive thymocytes but deleted from the cd4+ and cd8+ single positive populations. similar deletions were subsequently reported for v beta 8.1+ and v beta 6+ t cells in mls-1a mouse strains and for v beta 3+ t cells in mls-2a/3a strains. the 'mls antigens' are most effectively presented by h- ... | 1994 | 7863543 |
| dna binding activity of the glucocorticoid receptor is sensitive to redox changes in intact cells. | the effect of changes of redox conditions on glucocorticoid receptor (gr) activity in intact cells has been studied using two approaches. one was to evaluate the gr-dna binding in extracts of cos2 cells transiently overexpressing gr and in which reactive oxygen intermediates (roi) accumulate as a consequence of glutathione (gsh) depletion. gr-dna binding was significantly decreased in cos2 cells treated with diethylmaleate (dem), which causes gsh depletion by forming gsh-dem complexes. a similar ... | 1995 | 7873605 |
| an mmtv integration site on the centromere proximal region of mouse chromosome 11. | | 1994 | 7873889 |
| the overexpression of int-5/aromatase, a novel mmtv integration locus gene, is responsible for d2 mammary tumor cell proliferation. | our recent studies have shown that the cellular gene at the mouse mammary tumor virus (mmtv) integration site in the int-5 locus in balb/c d2 precancerous hyperplastic alveolar nodules is identical to the gene encoding aromatase (cyp19), a member of the cytochrome p450 gene superfamily. mmtv integrated within the 3' untranslated region of the aromatase gene is responsible for the overexpression of this gene (int-5/aromatase) in mammary tumors. this paper describes the biological significance of ... | 1995 | 7874687 |
| critical role of endogenous mtv in acute lethal graft-versus-host disease. | little is known about the etiology of the graft-versus-host disease (gvhd) occuring after transplantation of lymphoid cells incompatible for minor histocompatibility antigens (mhag). here, the potential role of host endogenous mouse mammary tumor virus (mtv)-encoded superantigens (sag) in the development of lethal gvhd was investigated. in a combination of h-2d compatible mice, the presence of mtv-7 and, to a lesser extent, of mtv-1, -6, -13 in the host genome, highly increases the rate and seve ... | 1995 | 7875197 |
| decreased tumor formation in 7,12-dimethylbenzanthracene-treated stromelysin-1 transgenic mice is associated with alterations in mammary epithelial cell apoptosis. | to determine the role of a specific member of the metalloproteinase family, stromelysin-1, in mammary carcinogenesis and tumor progression, transgenic mice expressing activated rat stromelysin-1 under the control of the mouse mammary tumor virus promoter/enhancer were treated with the carcinogen 7,12-dimethylbenzanthracene (dmba) to induce mammary tumors. surprisingly, the expression of stromelysin-1 during the time of dmba treatment reduced the number of mice developing mammary tumors, in parti ... | 1995 | 7882342 |
| the requirement for the basal transcription factor iie is determined by the helical stability of promoter dna. | the role of the basal transcription factor tfiie was investigated in rna polymerase ii transcription reactions reconstituted with purified proteins. using negatively supercoiled templates, which circumvent the requirement for tfiih, we observed that transcription from the adenovirus major-late (ml) core promoter is more dependent on tfiie than transcription from the adenovirus e4 (e4) or mouse mammary tumor virus (mmtv) promoters. for all three promoters, an increase in the ionic strength of the ... | 1995 | 7882984 |
| structural and functional studies of retroviral rna pseudoknots involved in ribosomal frameshifting: nucleotides at the junction of the two stems are important for efficient ribosomal frameshifting. | ribosomal frameshifting, a translational mechanism used during retroviral replication, involves a directed change in reading frame at a specific site at a defined frequency. such programmed frameshifting at the mouse mammary tumor virus (mmtv) gag-pro shift site requires two mrna signals: a heptanucleotide shifty sequence and a pseudoknot structure positioned downstream. using in vitro translation assays and enzymatic and chemical probes for rna structure, we have defined features of the pseudok ... | 1995 | 7882986 |
| fgf-8, activated by proviral insertion, cooperates with the wnt-1 transgene in murine mammary tumorigenesis. | we have used mouse mammary tumor virus (mmtv) infection of wnt-1 transgenic mice to accelerate mammary tumorigenesis and to molecularly tag insertionally activated proto-oncogenes that cooperate oncogenically with wnt-1 (g. m. shackleford, c. a. macarthur, h. c. kwan, and h. e. varmus, proc. natl. acad. sci. usa 90:740-744, 1993). here we report the identification and characterization of a 31-kb genomic locus that contains clonal mmtv integrations in 8 of 80 mammary tumors from mmtv-infected wnt ... | 1995 | 7884899 |
| processing and major histocompatibility complex binding of the mtv7 superantigen. | mouse mammary tumor viruses produce superantigens (vsags) which interact with class ii major histocompatibility complex (mhc) proteins and stimulate t cells. vsags are synthesized as type ii membrane proteins, but at least one of these proteins (vsag7) is found on the cell surface in a proteolytically processed form. monoclonal antibodies (mabs) were used to characterize vsag7 and its binding to class ii molecules. vsag7 is synthesized in the endoplasmic reticulum (er) as a 45 kd glycoprotein co ... | 1994 | 7889395 |
| nucleoprotein structure influences the response of the mouse mammary tumor virus promoter to activation of the cyclic amp signalling pathway. | recent studies have provided evidence of crosstalk between steroid receptors and cyclic amp (camp) signalling pathways in the regulation of gene expression. a synergism between intracellular phosphorylation inducers and either glucocorticoids or progestins has been shown to occur during activation of the mouse mammary tumor virus (mmtv) promoter. we have investigated the effect of 8-br-camp and okadaic acid, modulators of cellular kinases and phosphatases, on the hormone-induced activation of th ... | 1995 | 7891707 |
| cisplatin inhibits chromatin remodeling, transcription factor binding, and transcription from the mouse mammary tumor virus promoter in vivo. | the anticancer drug cis-diamminedichloro-platinum(ii) (cisplatin) covalently modifies dna, and these lesions are thought to lead to cell death by inhibiting dna and rna synthesis. by using in vivo analysis techniques, we have investigated the influence of cisplatin on hormone-induced transcription from the mouse mammary tumor virus (mmtv) promoter. cisplatin substantially reduced glucocorticoid-induced expression from the mmtv promoter stably incorporated into mouse tumor cells. the glucocortico ... | 1995 | 7892227 |
| insertional mutagenesis identifies a member of the wnt gene family as a candidate oncogene in the mammary epithelium of int-2/fgf-3 transgenic mice. | transgenic mice harboring the int-2/fgf-3 protooncogene under transcriptional control of the mouse mammary tumor virus (mmtv) promoter/enhancer exhibit a dramatic, benign hyperplasia of the mammary gland. in one int-2 transgenic line (tg.nx), this growth disturbance is evoked by pregnancy and regresses after parturition. regression of hyperplastic mammary epithelium is less complete after successive pregnancies, and, within 10 months, most tg.nx mice stochastically develop mammary carcinomas tha ... | 1995 | 7892260 |
| superantigens produced by infectious pathogens: molecular mechanism of action and biological significance. | "superantigens" have in common an extremely potent stimulatory activity for cd4+, cd8+, and some gamma delta+ t lymphocytes. superantigens use a unique mechanism: they crosslink variable parts of the t cell receptor with mhc class ii molecules on accessory or target cells. the interaction site on the t cell receptor is the variable part of the beta-chain (v beta). there are several reasons why these molecules have aroused such tremendous interest in recent years. first, they have provided key in ... | 1994 | 7894042 |
| direct binding of the mtv7 superantigen (mls-1) to soluble mhc class ii molecules. | the superantigen encoded by the mouse mammary tumor virus (mmtv) is a potent stimulator of t cells when bound to mhc class ii molecules. recent data from this laboratory have shown that the mtv7 superantigen, mls-1, elicits a strong t cell response when presented by hla-dr. to expand these observations further, we have produced the 28 kda extracellular domain and the 18 kda carboxy-terminal subfragment of the mls-1 protein in e. coli and studied their interaction with human mhc class ii molecule ... | 1995 | 7895171 |
| effect of ionizing radiation on the expression of chloramphenicol acetyltransferase gene under the control of commonly used constitutive or inducible promoters. | we examined the effect of ionizing radiation on the expression of the chloramphenicol acetyltransferase (cat) gene driven by commonly used viral or semi-synthetic promoters in transient transfection assays using cos-7 cells. specifically, we studied the constitutive early promoters of cytomegalovirus (cmv), rous sarcoma virus (rsv), and the simian virus 40 (sv40), and the inducible promoters from mouse mammary tumour virus (mmtv, inducible by dexamethasone) and the semi-synthetic svlaco promoter ... | 1995 | 7897274 |
| transcription of multiple exogenous mouse mammary tumor viruses in a single mammary tumor of an shn mouse. | the shn mouse strain, established in japan independently from other mammary tumor-prone strains, is known to have a very high incidence of early-onset mammary tumors. in this study, we demonstrate that exogenous mouse mammary tumor virus (mmtv) plays a crucial role in early-onset mammary tumorigenesis in this strain. we subsequently isolated mmtv rna from a mammary tumor of an shn female mouse, reverse transcribed it, and amplified a 1.2-kb coding region of the long terminal repeat (ltr) by use ... | 1994 | 7898031 |
| mammary tumors expressing the neu proto-oncogene possess elevated c-src tyrosine kinase activity. | amplification and overexpression of the neu (c-erbb2) proto-oncogene has been implicated in the pathogenesis of 20 to 30% of human breast cancers. although the activation of neu receptor tyrosine kinase appears to be a pivotal step during mammary tumorigenesis, the mechanism by which neu signals cell proliferation is unclear. molecules bearing a domain shared by the c-src proto-oncogene (src homology 2) are thought to be involved in signal transduction from activated receptor tyrosine kinases su ... | 1994 | 7903421 |
| evolution of mouse mammary tumor virus-related sequences in the human genome. | the human genome contains numerous copies of elements with sequence homology to the mouse mammary tumor virus (mmtv). we have been interested in whether these elements are still actively transposing in the germ lines, and investigated this question by looking at restriction fragment patterns. genomic dna from humans and selected animals were digested with three different restriction enzymes and hybridized with five probes representative of five subgroups of the human mmtv-related elements. two p ... | 1993 | 7903503 |
| a v beta 8.2-specific superantigen from exogenous mouse mammary tumor virus carried by fm mice. | a number of endogenous mouse mammary tumor virus (mmtv) proviruses encode superantigen that have the ability to stimulate t cells with a certain t cell receptor (tcr) beta-chain variable region (v beta) and to mediate the v beta-specific clonal deletion. the tumorigenic milk-borne mmtv carried by c3h and gr mice also have superantigenic properties in vivo. in the present study we identified and characterized a novel v beta 8.2-specific superantigen of exogenous mmtv carried by fm mice. the open ... | 1994 | 7913038 |
| transmission of an mls-1a-like superantigen to balb/c mice by foster-nursing on f1 mls-1bxa mothers. sex-influenced onset of clonal deletion. | foster nursing of balb/c (mls-1b) mice on (balb/cxakr/j)f1 and (balb/cxdba/2)f1 (mls-1bxa), but not on (balb/cxc57bl/6)f1 or (balb/cxc3h/he)f1 (mls-1bxb mothers, induced the progressive deletion of v beta 6+ and v beta 8.1+ t cells in 50% of the litter. the onset of this mls-1a-like clonal deletion was markedly sex-influenced, being earlier in females (8-10 wk of age) than in males (32 wk). in both sexes, cd4+ v beta 6+ cells were more affected than cd8+ v beta 6+ cells. decreases in the percent ... | 1994 | 7913941 |
| dimerization characteristics of the dna- and steroid-binding domains of the androgen receptor. | the dna-binding domain (dbd) of the androgen, mineralocorticoid, and glucocorticoid receptors and the steroid-binding domain (sbd) of the androgen receptor (ar) were expressed separately as fusion proteins with glutathione-s-transferase (gst) in escherichia coli. native polyacrylamide gel electrophoresis and gel exclusion hplc demonstrated that the gst-ardbd fusion protein was present as a dimer. on the other hand, the gst-arsbd fusion protein formed a high-molecular weight oligomer, which seeme ... | 1994 | 7918108 |
| mouse mammary tumor virus superantigens and murine autoimmune gastritis. | neonatal thymectomy induces autoimmune gastritis in balb/c (minor lymphocyte-stimulating antigen [mls]-1b) mice, whereas dba/2 (mls-1a) mice are resistant. resistance has been linked to the mls-1a locus, which encodes a retroviral superantigen, and to superantigen reactive t cells that express v beta 6+ t-cell receptors. v beta 6+ t cells are known to be deleted in mice expressing mls-1a superantigens. | 1994 | 7926482 |
| conditional expression of human tnf-alpha: a system for inducible cytotoxicity. | tumour necrosis factor-alpha (tnf-alpha) is currently being used in clinical trials for cancer treatment, but toxic side effects, due to systemic administration and high doses, are observed. inducible expression of tnf may permit selective killing of tumour cells in gene therapy protocols without need for prolonged and/or high-level tnf expression. a conditional tnf expression vector has been constructed in which the coding sequences of human tnf have been placed under the transcriptional contro ... | 1994 | 7927889 |
| regulation of the mouse mammary tumor virus receptor by phosphorylation and internalization in mammary epithelial cells. | the mouse mammary tumor virus enters mammary epithelial cells via a plasma membrane protein that binds to a viral envelope glycoprotein, gp52. in intact cells, this gp52 receptor can be phosphorylated by activators of protein kinase a and protein kinase c (pkc), but this modification does not occur in response to epidermal growth factor, whose receptor is a tyrosine kinase, or to gp52. phosphorylation of the gp52 receptor rapidly leads to internalization and gradual loss of binding activity. bot ... | 1994 | 7929597 |
| retroviral infection of neonatal peyer's patch lymphocytes: the mouse mammary tumor virus model. | mouse mammary tumor virus is known to infect newborn mice via mother's milk. a proposed key step for viral spread to the mammary gland is by the infection of lymphocytes. we show here that although in suckling mice retroviral proteins are found in all epithelial cells of the gut, viral dna is exclusively detectable in the peyer's patches. as early as 5 d after birth the infection leads to a superantigen response in the peyer's patches but not in other lymphoid organs draining the intestine. vira ... | 1994 | 7931081 |
| cell lines inducibly expressing the adeno-associated virus (aav) rep gene: requirements for productive replication of rep-negative aav mutants. | the adeno-associated virus (aav) rep gene codes for a family of nonstructural proteins which are required for aav gene regulation and dna replication. in addition, rep has been implicated in a variety of activities outside the aav life cycle which have been difficult to study, since attempts to achieve separate and constitutive expression of rep in stable cell lines have failed so far. here we report the generation of two cell lines which inducibly express rep78 under the control of the glucocor ... | 1994 | 7933099 |
| novel activating mutations in the neu proto-oncogene involved in induction of mammary tumors. | amplification of the neu/c-erbb-2 receptor tyrosine kinase has been implicated as an important event in the genesis of human breast cancer. indeed, transgenic mice bearing either an activated form of neu or the wild-type proto-oncogene under the transcriptional control of the mouse mammary tumor virus promoter-enhancer frequently develop mammary carcinomas (l. bouchard, l. lamarre, p. j. tremblay, and p. jolicoeur, cell 57:931-936, 1989; c. t. guy, m. a. webster, m. schaller, t. j. parson, r. d. ... | 1994 | 7935422 |
| detection of transcription factor binding in vivo using lambda exonuclease. | | 1994 | 7937164 |
| relative glucocorticoid potency revisited. | to determine the relative potency of synthetic glucocorticoids, glucocorticoid receptor expressing cells were transfected with a hormone-inducible reporter gene, and were cultured in the presence of various glucocorticoid ligands. hormonal inducibility was determined by means of a chloramphenicol acetyltransferase assay. dexamethasone and prednisolone, as well as cortisol, induced the expression of the reporter gene in a dose-dependent fashion. the relative potency of each ligand was in this ord ... | 1994 | 7939139 |
| genome organization of a biologically active molecular clone of the lymphoproliferative disease virus of turkeys. | the lymphoproliferative disease retrovirus (lpdv) induces an acute, horizontally transmitted disease of turkeys that is often fatal. although lpdv cannot be grown in cultured cells, it was possible to isolate molecular clones of biologically active integrated proviral genomes from spleens of infected turkeys. based upon molecular hybridization and nucleotide sequence comparisons of its pol gene, lpdv was shown to represent a distinct group of avian retroviruses most closely related to avian sarc ... | 1994 | 7941337 |
| 11 beta-hydroxysteroid dehydrogenase activity in human lung cells and transcription regulation by glucocorticoids. | selectivity to aldosterone (aldo) in mineralocorticoid target tissues has been suggested to be due to the activity of 11 beta-hydroxysteroid dehydrogenase (11 beta-hsd). this enzyme inactivates the endogenous glucocorticoid cortisol, thus permitting the unhindered access of aldo to the mineralocorticoid receptor. the 11 beta-hsd activity was measured by the conversion of cortisol to cortisone and vice versa. concomitant treatment of the cells with either cortisone or cortisol in the presence of ... | 1994 | 7943349 |
| two independent pathways for transcription from the mmtv promoter. | the influence of progesterone receptor (pr) and glucocorticoid receptor (gr) on transcription from the mouse mammary tumour virus (mmtv) promoter was analyzed using cell-free transcription of dna templates with a g-free cassette. preincubation of the templates with either pr or gr stimulates the rate of transcription initiation 10-50 fold, whereas the recombinant dna binding domain of gr is inactive. mutations that inactivate the nuclear factor i (nfi) binding site, or nfi depletion of the nucle ... | 1994 | 7947347 |
| transcription activation of mouse mammary tumor virus-chloramphenicol acetyltransferase: a model to study the metabolism of cortisol. | the human 11 beta-hydroxysteroid dehydrogenase (h11 beta-hsd) inactivates the active corticosteroid cortisol to its inactive metabolite cortisone. we have developed transactivation analyses of the reporter chimeric gene mouse mammary tumor virus-chloramphenicol acetyltransferase (mmtv-cat) to study the catalytic activity of h11 beta-hsd introduced by cotransfection into receptor and 11 beta-hsd deficient cv-1 cells. assay of 11 beta-hsd expressed in cv-1 cells by cotransfection showed that the c ... | 1994 | 7947689 |
| the establishment of the long terminal repeat of the mouse mammary tumor virus into cv-1 cells allows a functional analysis of steroid receptors. | to analyze in situ the effects of mineralocorticoid receptor (mr) on the nucleo-protein organization of the target mmtv promoter, we have established a new cell line by integrating in cv-1 cells a construct containing the long terminal repeat of the mouse mammary tumor virus (mmtv-ltr). the mmtv-ltr contains glucocorticoid response elements (gres), known to interact with mr. cv-1 cells were selected because they lack glucocorticoid receptor (gr). the absence of gr in the host cell line allows th ... | 1994 | 7948018 |
| the androgen receptor in the testicular feminized (tfm) mouse may be a product of internal translation initiation. | androgen insensitivity in the testicular feminized (tfm) mouse is caused by frame-shift mutation in the androgen receptor (ar) mrna, which results in a stop codon in the amino terminus. despite this mutation, a smaller sized protein corresponding to the dna- and steroid-binding domain of the ar can be synthesized from the cloned tfm ar cdna by in vitro translation. the tfm ar construct was demonstrated to express a protein capable of binding androgen with an affinity similar to the cloned wild-t ... | 1994 | 7950980 |
| influence of chromatin structure on the binding of transcription factors to dna. | | 1993 | 7956078 |
| hormone binding domain of human glucocorticoid receptor. enhancement of transactivation function by substitution mutants m565r and a573q. | to determine the importance of specific amino acids in the hormone-binding domain of the human glucocorticoid receptor (hgr), we have generated mutants m565r, g567a, and a573q. in hormone binding assays using [3h]cortisol, half-maximal saturation of dexamethasone competition was achieved at 10 pm with hgr m565r and hgra573q compared to 10 nm with wild type hgr. similar results were obtained in competition assays with [3h]dexamethasone and the glucocorticoid antagonist ru 486. the substitution mu ... | 1994 | 7961865 |
| expression of two structurally identical viral superantigens results in thymic elimination at distinct developmental stages. | mouse mammary tumor virus proviral integrants encode superantigens. developing thymocytes bearing tcrs with particular v beta elements encounter these endogenous viral superantigens as self molecules in the thymus and are consequently clonally eliminated. to study this mechanism of tolerance induction, we have bred b10.br-mtv-1 and b10.br-mtv-6 mice, which carry either mtv-1 or mtv-6 proviruses but are otherwise genetically identical. the protein products of these mouse mammary tumor virus integ ... | 1994 | 7963568 |
| t cell receptor-major histocompatibility complex class ii interaction is required for the t cell response to bacterial superantigens. | bacterial and retroviral superantigens (sags) stimulate a high proportion of t cells expressing specific variable regions of the t cell receptor (tcr) beta chain. although most alleles and isotypes bind sags, polymorphisms of major histocompatibility complex (mhc) class ii molecules affect their presentation to t cells. this observation has raised the possibility that a tcr-mhc class ii interaction can occur during this recognition process. to address the importance of such interactions during s ... | 1994 | 7964467 |
| targeting of promoters for trans activation by a carboxy-terminal domain of the ns-1 protein of the parvovirus minute virus of mice. | the ns-1 gene of the parvovirus minute virus of mice (mvm) (prototype strain, mvmp) was fused in phase with the sequence coding for the dna-binding domain of the bacterial lexa repressor. the resulting chimeric protein, lexns-1, was tested for its transcriptional activity by using various target promoters in which multiple lexa operator sequences had been introduced. under these conditions, ns-1 was shown to stimulate gene expression driven by the modified long terminal repeat promoters (from th ... | 1994 | 7966588 |
| [recent progress in superantigen research]. | in 1993 there was substantial progress in superantigen research. the following are the main achievements. (i) the life cycle of an exogenous mouse mammary tumor virus, mmtv (sw), has been clearly eluciated. (ii) x-ray crystallography of toxic shock syndrome toxin 1 has been completed. (iii) the involvement of a superantigen encoded by an endogenous mouse mammary tumor virus, mtv-51, in the development of a b cell lymphoma has been shown in sjl mice. however, there are many unsolved questions. fo ... | 1994 | 7967097 |
| antiprogestins prevent progesterone receptor binding to hormone responsive elements in vivo. | antiprogestins inhibit progesterone action by competing for binding to the progesterone receptor and are potentially important pharmaceuticals in fertility control and cancer therapy. why the complex of antiprogestins and progesterone receptor is functionally inactive is unclear. present models are based on indirect evidence, such as transfection competition assays and in vitro dna binding studies, partly because of difficulties in visualizing the receptor bound to dna in vivo. here we used geno ... | 1994 | 7972059 |
| cloning in a plasmid of an mmtv from a wild chinese mouse: sequencing of the viral ltr. | plasmid subcloning by conventional techniques of full length exogenous mouse mammary viruses (mmtv) has not been realized because of the involvement of host-mediated structural changes in the viral gag gene. to circumvent this problem, an alternative subcloning method, excision of phagemid (pbluescript sk) from lambda zap ii, was successfully used to subclone a novel exogenous mmtv (jyg-mmtv) provirus fragment containing an intact gag gene. sequence analysis revealed that the ltr of this virus i ... | 1994 | 7975881 |
| overexpression of estrogen receptor in htb 96 human osteosarcoma cells results in estrogen-induced growth inhibition and receptor cross talk. | estrogenic effects on the proliferation and differentiated cellular functions of bone cells have been described in vivo and in vitro. in particular, stimulatory effects on the growth rate of osteoblasts have been observed, although these are generally small. in an attempt to produce a more sensitive model for the study of estrogen action in bone, htb 96 human osteoblast-like osteosarcoma cells, which lack endogenous estrogen receptor (er), were stably transfected with an expression vector coding ... | 1994 | 7976507 |
| regulation of transcription by steroid hormones. | | 1994 | 7978858 |
| systematic identification of h-2 kd binding peptides and induction of peptide specific ctl. | most peptides with putative mhc i restricted sequence motifs do not bind to the corresponding mhc i nor induce cytolytic t cells. there exist additional constraints which limit peptide binding and immunogenicity. to identify immunogenic peptides in novel protein sequences, it will be necessary to first evaluate peptide binding to mhc i. in this study, a soluble single chain fusion protein sc-kd was used to evaluate potential kd binding peptides from the sequences of mouse mammary tumor virus gag ... | 1994 | 7983382 |
| ectopic vasopressin expression in mmtv-wnt-1 transgenic mice modifies mammary tumor differentiation and pathology. | a transgenic mouse model has been developed to test the involvement of ectopic neuropeptide production as a secondary factor in cancer. mice bearing a mouse mammary tumor virus-vasopressin (mmtv-vp) fusion transgene synthesized authentic vasopressin in mammary ducts and alveoli, but this had no effect on mammary gland development and growth. mice bearing the mmtv-vp transgene were then mated with mice bearing the mmtv-wnt-1 transgene to produce bitransgenic animals. two types of mammary tumor de ... | 1994 | 7987839 |
| the 5' enhancer of the mouse mammary tumor virus long terminal repeat contains a functional ap-2 element. | the mouse mammary tumor virus (mmtv) retrovirus causes mammary adenocarcinomas in mice by proviral insertion near members of the wnt family of proto-oncogenes, leading to their deregulation and cellular transformation. the 5' end of the mmtv long terminal repeat (ltr) has been implicated in tissue-specific activation of these genes. in this study, we characterize an enhancer element (ban2; -1075 to -978) at the 5' end of the mmtv ltr. we show that this enhancer is 5-fold more active in a murine ... | 1994 | 7989375 |
| [analysis of the sequence of the endogenous djungarian hamster provirus (mrs-ps) related to the murine mammary cancer virus]. | the complete nucleotide sequence of the dwarf hamster endogenous retrovirus (mrs-ps) related to the mouse mammary tumor virus is presented. mrs-ps has a typical retroviral structure, it is 6980 bp long with ltrs of ca. 880 base pairs at both ends. ltrs carry the usual signals for transcription control. mrs-ps genes had formerly coded for viral proteins (protease, revertase, and envelope proteins) but have been spoiled by numerous point mutations. evolutionary relationships with other retroviruse ... | 1994 | 7990818 |
| the effect of mouse mammary tumor virus receptor activation on mammary epithelial cell sensitivity toward prolactin. | mammary epithelial cells infected with the mouse mammary tumor virus (mmtv) require less than one-half the concentration of prolactin to elicit alpha-lactalbumin production than uninfected tissue (ec50 = 89 +/- 10 ng/ml vs. 206 ng/ml, respectively). furthermore, stimulating antibodies to the cellular receptor for mmtv halved the prolactin requirement of mmtv-tissue, while mmtv antibodies that sequestered secreted mmtv increased the prolactin requirement in mmtv+ tissue. these data suggest that t ... | 1994 | 7999074 |
| targeted disruption of int-2 (fgf-3) causes developmental defects in the tail and inner ear. | the int-2 gene (also designated fgf-3) was originally identified because its transcription is activated by the nearby integration of mouse mammary tumor virus in virus-induced tumors. molecular analyses have revealed that the int-2 gene produces at least four mrnas, all of which encode a protein that has 40-50% amino acid sequence similarity with the fibroblast growth factors (fgfs). int-2 gene expression is localized to a small number of discrete sites in the developing mouse, but has not been ... | 1994 | 7999362 |
| dietary regulation of mammary tumorigenesis in riii/sa mice: investigation of a possible mechanism. | the effects of caloric restriction on the incidence of mammary tumor development, the levels of the expression of mouse mammary tumor virus (mmtv)- and prolactin-rna, as well as the levels of serum prolactin, were investigated in virgin riii/sa mice, a strain known to display a high incidence of spontaneous mammary tumor development. of the 54 mice fed a low-calorie (lc; 10 kcal/day) diet containing low fat (lf; 5% corn oil) for a period of 72 weeks, only seven mice were found to develop mammary ... | 1994 | 8019980 |
| negative segregation of mtv loci in h-2e+ mice selected for high antibody response. | endogenous mouse mammary tumor proviruses (mtvs) encode superantigens (sags), which can delete t lymphocytes expressing particular tcrb-v genes when associated with the h-2e molecule. in the present work, distribution of mtvs was investigated in six independent pairs of mouse lines genetically selected for high (h) or low (l) ab production to specific t-cell-dependent ags. these experiments were performed to evaluate the role of mtv-encoded sags in the determination of h and l phenotypes. no sys ... | 1994 | 8026861 |
| structural analysis of the ras transgene in mmtv/v-ha-ras transgenic mice. | transgenic animals are becoming increasingly important in laboratory animal research. in cancer research, the role of specific genes in tumorigenesis can be directly tested in live animals by using transgenic animal technology. since dna-damaging carcinogens are not required to initiate tumors in transgenic animals, these models are particularly useful in the analysis of genetic alterations associated with tumorigenesis. southern blot analysis was used to assess the copy number, structure, and m ... | 1994 | 8028274 |
| identification of a high-molecular-weight cellular protein complex containing the adenovirus dna binding protein. | the adenovirus dna binding protein (dbp) functions in a number of diverse processes that include viral dna replication and host range determination. a subpopulation of dbp has been found to exist in a high-molecular-weight (hmwdbp) complex of greater than 650 kda. this complex was stable to high salt and low levels of detergent in the presence of dtt at 4 degrees. while the complex prepared in high salt was devoid of nucleic acid, it retained its ability to bind to ssdna. electron microscopic (e ... | 1994 | 8030235 |
| insertional mutation of int protooncogenes in the mammary tumors of a new strain of mice derived from the wild in china: normal- and tumor-tissue-specific expression of int-3 transcripts. | a new mouse strain, mus musculus jyg, has been isolated from the wild in china. after several generations of inbreeding, jyg mice have been found to develop mammary adenocarcinomas at a high incidence (70-80%). in order to understand the mechanism by which mammary tumors are induced in these mice, we analyzed 23 available mammary tumors and liver tissues with regard to mouse mammary tumor virus (mmtv) proviral integrations and the pattern of int oncogene (wnt-1, int-2/fgf-3, and int-3) rearrange ... | 1994 | 8030284 |
| transcriptional activation by viral enhancers: critical dependence on extracellular matrix-cell interactions in mammary epithelial cells. | extracellular matrix (ecm)-cell interactions are essential for the regulation of many genes in differentiated cell types. a number of expression vectors that work well in cells cultured on tissue-culture plastic appear to be inactive or sporadically active in vivo. we reasoned that these responses also may be influenced by the ecm. we therefore examined three commonly used viral enhancers and found that they all responded either positively or negatively to the presence of exogenous ecm. using mo ... | 1994 | 8031466 |
| 11 beta-hydroxysteroid dehydrogenase and tissue specificity of androgen action in human prostate cancer cell lncap. | incubation of whole lncap cells in suspension with tritium labeled cortisol revealed two major and one minor radioactive product. of the major products, one migrated with an rf value identical to cortisol (kendall's compound "f"), and the second migrated with an rf value similar to nonradioactive cortisone (kendall's compound "e"); the third minor product comigrated with 21-acetylated cortisol. the conversion of cortisol to cortisone was linear with respect to cell number, and conversion reached ... | 1994 | 8031714 |
| coexpression of exogenous and endogenous mouse mammary tumor virus rna in vivo results in viral recombination and broadens the virus host range. | mouse mammary tumor virus is a replication-competent b-type murine retrovirus responsible for mammary gland tumorigenesis in some strains of laboratory mice. mouse mammary tumor virus is transmitted horizontally through the milk (exogenous or milk-borne virus) to susceptible offspring or vertically through the germ line (endogenous provirus). exogenously acquired and some endogenous mouse mammary tumor viruses are expressed at high levels in lactating mammary glands. we show here that there is p ... | 1994 | 8035502 |
| ribozyme mediated degradation of beta-amyloid peptide precursor mrna in cos-7 cells. | two sets of eucaryotic expression vectors encoding trans-acting hammerhead ribozymes and trans-acting hairpin ribozymes were constructed. in one set of vectors ribozyme rna transcription was placed under the control of a mouse mammary tumor virus long terminal repeat (mmtv-ltr). in the other set ribozyme expression was controlled by a metallothionein iia (mt-iia) promoter. each ribozyme was directed to the first target sequence in the alzheimer amyloid peptide precursor mrna (beta app mrna), 5' ... | 1994 | 8036167 |
| potentiation of glucocorticoid receptor-mediated gene expression by heat and chemical shock. | we have examined the effects of heat shock on glucocorticoid receptor (gr)-mediated gene transcription in an l929 cell line derivative (lmcat2) stably transfected with the mouse mammary tumor virus-chloramphenicol acetyltransferase (mmtv-cat) reporter plasmid. exposure of the lmcat2 cells to heat or chemical shock resulted in a large increase in dexamethasone (dex)-induced expression of cat enzyme activity. this potentiation of hormone-induced mmtv-cat expression was dependent on the magnitude o ... | 1994 | 8052262 |
| phenylalanine-780 near the c-terminus of the mouse glucocorticoid receptor is important for ligand binding affinity and specificity. | site-directed mutagenesis was employed to make two single amino acid substitutions for highly conserved amino acid residues near the c-terminus of the 783-amino acid mouse glucocorticoid receptor. substitution of leucine for histidine-781 caused little or no change in the concentration of dexamethasone required for half-maximal activation of a chloramphenicol acetyltransferase reporter gene expressed from a mouse mammary tumor virus promoter. however, when phenylalanine-780 was changed to alanin ... | 1994 | 8052263 |
| involvement of ets-related proteins in hormone-independent mammary cell-specific gene expression. | regulatory regions have been located in the 5' flanking sequence of the mouse whey acidic protein gene which contribute to its tissue- and stage-specific expression in the mammary gland. they can be functionally separated into elements which mediate the action of lactogenic hormones prolactin and glucocorticoids and elements which control mammary cell-specific transcription in the absence of hormones. by mutational analysis, we have located a site in the whey acidic protein promoter between -120 ... | 1994 | 8055977 |
| new infectious mammary tumor virus superantigen with v beta-specificity identical to staphylococcal enterotoxin b (seb). | only few infectious mouse mammary tumor viruses (mmtv) have been characterized which induce a potent superantigen response in vivo. here we describe the characterization of an mmtv which was isolated from milk of the highly mammary tumor-prone shn mouse strain. exposure of newborn mice to milk-borne mmtv (shn) results in a very slow deletion of v beta 7, 8.1, 8.2 and 8.3 expressing peripheral t cells. subcutaneous injection of adult mice with this virus induces a rapid and strong stimulation of ... | 1994 | 8056034 |
| differential steroid hormone induction of transcription from the mouse mammary tumor virus promoter. | the mouse mammary tumor virus (mmtv) contains sequences in its proximal promoter region to which both glucocorticoid and progesterone receptors can bind. in transient transfection experiments both hormones are able to stimulate transcription from reporter plasmids containing either native or consensus hormone response elements (glucocorticoid response element/progesterone response element). previous experiments have demonstrated that the mmtv long terminal repeat is reproducibly assembled into a ... | 1994 | 8058066 |
| depletion of nuclear poly(adp-ribose) polymerase by antisense rna expression: influences on genomic stability, chromatin organization, and carcinogen cytotoxicity. | poly(adp-ribose) polymerase (padprp) catalyzes the transfer of multiple adp-ribose units from nad to nuclear histone and nonhistone proteins, a reaction that appears to be important in the rejoining of dna strand breaks during dna repair and replication. we previously established and characterized a hela cell line that was stably transfected with a recombinant expression plasmid containing the mouse mammary tumor virus promoter upstream of a construct encoding padprp antisense rna. we now show t ... | 1994 | 8062255 |
| differential transformation of mammary epithelial cells by wnt genes. | the mouse wnt family includes at least 10 genes that encode structurally related secreted glycoproteins. wnt-1 and wnt-3 were originally identified as oncogenes activated by the insertion of mouse mammary tumor virus in virus-induced mammary adenocarcinomas, although they are not expressed in the normal mammary gland. however, five other wnt genes are differentially expressed during development of adult mammary tissue, suggesting that they may play distinct roles in various phases of mammary gla ... | 1994 | 8065359 |