| a transient assay for gene expression studies in b lymphocytes and its use for superantigen assays. | superantigen assays are used to determine the stimulation of classes of t cells in response to the presence of a superantigen. this requires that antigen-presenting cells, such as b-lymphocytes, are co-cultured with syngeneic t cells over a four-day period. this prerequisite rules out conventional transient transfection procedures, since the cells must remain metabolically active for around five days. consequently, stably transfected b cells have previously been used to test recombinant dna cons ... | 1994 | 8068343 |
| activity assays of nine heterogeneous promoters in neural and other cultured cells. | to express high levels of proteins encoded by transfected dna constructs in a variety of cultured cells, including neuronal cells, the activities of nine different promoters were evaluated using escherichia coli beta-galactosidase (beta-gal) (lacz) as a reporter gene. these nine promoters were categorized into three distinct groups (high, intermediate, and low expresser), in terms of the levels of beta-gal expression. an expression vector containing the cytomegalovirus enhancer and the chick bet ... | 1994 | 8069455 |
| gene ecology: a cis-acting gene-to-gene interaction due to the spatial arrangement of genes in chromosomes affects neighbouring transfected c-h-ras expression. | a cis-acting interference between gene activities, which occurs when two genes lie on the same dna strand and have an intergenic distance less than a defined length, was previously deduced when chromosomal organizations of various higher eukaryote nuclear genes in clusters were compared. in order to investigate such an interference due to arrangement of genes along chromosomes, we have isolated a few cell lines which possessed (i) human mutated c-h-ras fused with the mouse mammary tumour virus l ... | 1994 | 8069461 |
| the mineralocorticoid receptor discriminates aldosterone from glucocorticoids independently of the 11 beta-hydroxysteroid dehydrogenase. | to investigate the mechanisms involved in the in vivo aldosterone selectivity of the mineralocorticoid receptor (mr), we studied the respective contribution of the receptor and the enzyme 11 beta-hydroxysteroid dehydrogenase (11hsd), which converts glucocorticoids into inactive metabolites. using a cotransfection assay in cv-1 cells, aldosterone activated mouse mammary tumor virus promoter through human mr (hmr) with an ed50 of 0.01 nm. an at least 100-fold higher concentration of cortisol (f), ... | 1994 | 8070376 |
| nucleosome positioning and modification: chromatin structures that potentiate transcription. | the role of the nucleosome in the folding of dna has often been thought of as purely a packaging one. however, the precise folding of regulatory sequences of genes around the histones within positioned nucleosomes is also important in controlling both the access of transcription factors to chromatin and the transcription process itself. this review highlights these functions by using specific examples of an active and regulatory role for positioned nucleosomes. | 1994 | 8073501 |
| antizyme delays the restoration by spermine of growth of polyamine-deficient cells through its negative regulation of polyamine transport. | effects of antizyme on polyamine transport and spermine restoration of the growth of polyamine-deficient cells were examined by using mouse fm3a cells transfected with pmamneoz1 possessing rat antizyme cdna under the control of glucocorticoid-inducible promoter. treatments of the transfected cells with alpha-difluoromethylornithine (dfmo), an inhibitor of ornithine decarboxylase (odc), and dexamethasone, an inducer of antizyme, both caused a decrease in odc activity and polyamine contents and in ... | 1994 | 8074711 |
| drosophila wingless: a paradigm for the function and mechanism of wnt signaling. | the link between oncogenesis and normal development is well illustrated by the study of the wnt family of proteins. the first wnt gene (int-1) was identified over a decade ago as a proto-oncogene, activated in response to proviral insertion of a mouse mammary tumor virus. subsequently, the discovery that drosophila wingless, a developmentally important gene, is homologous to int-1 supported the notion that int-1 may have a role in normal development. in the last few years it has been recognized ... | 1994 | 8080429 |
| a new gene encoding the ligand for deletion of t cells bearing tcrb-v6 and v8.1 (mtv-50). | | 1994 | 8082898 |
| tumours of the mammary gland. | | 1994 | 8082918 |
| the cytotoxicity of the autonomous parvovirus minute virus of mice nonstructural proteins in fr3t3 rat cells depends on oncogene expression. | the nonstructural (ns) proteins of the autonomous parvovirus minute virus of mice are involved in viral dna replication and in the regulation of homologous and heterologous promoters. moreover, ns products have proved to be cytotoxic, especially for transformed cells. we show here that intracellular accumulation of ns products is not sufficient to kill rat fibroblasts from the established cell line fr3t3, which is phenotypically normal in several respects. frns cell lines were obtained by stable ... | 1994 | 8083981 |
| the delayed glucocorticoid-responsive and hepatoma cell-selective enhancer of the rat arginase gene is located around intron 7. | liver-selective transcription of the gene for rat arginase, an ornithine cycle (urea cycle) enzyme, is induced by glucocorticoids in a delayed secondary manner; the mrna induction by the hormones requires de novo protein synthesis, and is preceded by a time lag of several hours. we searched for a dna element mediating the glucocorticoid induction of the arginase gene with a transient transfection system using hepatoma cell lines. within the 233-base pair region that is located 11 kilobases downs ... | 1994 | 8089096 |
| the bovine papillomavirus e1 protein alters the host cell cycle and growth properties. | a stable e1-expressing cell line, ce1, was developed to investigate the effect of bovine papillomavirus e1 protein on host cell growth. expression of e1 in ce1 cells is under control of the dexamethasone-inducible mouse mammary tumor virus ltr promoter. flow cytometry was used to determine the intracellular levels of e1 in ce1 cells in parallel with cell cycle distributions and cell growth parameters. ce1 cells expressed a basal level of e1 that was increased following exposure to increasing con ... | 1994 | 8091648 |
| the protein p30, encoded at the gag-pro junction of mouse mammary tumor virus, is a dutpase fused with a nucleocapsid protein. | a ribosomal frameshift at the gag-pro junction of mouse mammary tumor virus (mmtv) gives rise to the protein p30. the protein consists of two domains, the zinc-finger-containing nucleocapsid (nc) protein portion with 95 residues and a c-terminal extension comprising 154 residues. the c-terminal domain shows similarity in sequence with the enzyme dutpase from other sources. in this paper, we demonstrate that p30 is a functional dutpase. overproduction of the nc protein in escherichia coli, using ... | 1994 | 8091672 |
| chemical effects in transgenic mice bearing oncogenes expressed in mammary tissue. | three transgenic mouse lines carrying v-ha-ras (tg-sh), c-myc (tg-m) or c-neu (tg-nk) oncogenes under regulatory control of mouse mammary tumor virus (mmtv) long terminal repeat (ltr) sequences were evaluated for responses to two chemical carcinogens. p-cresidine, a mutagenic urinary bladder carcinogen, increased the incidence of urinary bladder carcinomas in males and females in all three lines, and these tumors occurred at comparable incidences and grade in transgenic and non-transgenic mice. ... | 1993 | 8093862 |
| superantigen-reactive cd4+ t cells are required to stimulate b cells after infection with mouse mammary tumor virus. | superantigens are defined by their ability to stimulate a large fraction of t cells via interaction with the t cell receptor (tcr) v beta domain. endogenous superantigens, classically termed minor lymphocyte-stimulating (mls) antigens, were recently identified as products of open reading frames (orf) in integrated proviral copies of mouse mammary tumor virus (mmtv). we have described an infectious mmtv homologue of the classical endogenous superantigen mls-1a (mtv-7). the orf molecules of both t ... | 1993 | 8093892 |
| a strategy for constructing inducible expression plasmids for t-lymphocytes. | | 1993 | 8094284 |
| association of a v beta 2-specific superantigen with a tumorigenic milk-borne mouse mammary tumor virus. | a number of endogenous mouse mammary tumor virus (mmtv) proviruses encode superantigens that have the property of stimulating mature t lymphocytes in a tcr v beta-specific fashion and of mediating v beta-specific clonal deletion in developing t cells. the tumorigenic milk-borne mmtv carried by c3h and gr mice also have superantigen properties in vivo, and it has been proposed that this superantigenic function is critical to the infectivity and/or tumorigenicity of the virus. to test the requirem ... | 1993 | 8094408 |
| an activated allele of the c-erbb-2 oncogene impairs kidney and lung function and causes early death of transgenic mice. | the pathogenicity of the human c-erbb-2 oncogene was evaluated in transgenic mice. a dna sequence comprising the promoter-enhancer region of the mmtv ltr and a constitutively activated allele of the human c-erbb-2 growth factor receptor gene was introduced into the germ line of mice. expression of the transgene was observed in kidney, lung, mammary gland, salivary gland, harderian gland, and in epithelial cells of the male reproductive tract. all transgenic mice expressing the c-erbb-2 receptor ... | 1993 | 8100231 |
| a kinetic study on the deletion of thymic, peripheral, and gut-associated v beta 6+ t cells in an mls-1b balb/c colony infected with an exogenous mouse mammary tumor virus. | mls-1a expression results in the deletion of t cells bearing v beta 6 chains of the tcr. however, v beta 6+ t cells are also deleted in mls-1b balb/c mice that have been infected with an exogenous mouse mammary tumor virus (swiss mice) via maternal milk intake, and whose open reading frame region is markedly similar to that of the provirus mtv-7. in this report we describe the kinetics of v beta 6+ t cell deletion in the thymus, spleen, lymph nodes, and gut-associated lymphoid populations of the ... | 1993 | 8101538 |
| potentiation of glucocorticoid-mediated induction of the mouse mammary tumor virus promoter in mammary carcinoma cells by activation of protein kinase c. | in a mammary carcinoma cell line, the glucocorticoid induction of a stably integrated mouse mammary tumor virus-luciferase reporter gene is potentiated up to ten-fold by treatment of the cells with phorbol ester tumor promoters. this potentiation is stereospecific and is observed with a structurally unrelated tumor promoter that also activates protein kinase c. another tumor promoter, thapsigargin, that acts via mobilization of intracellular calcium stores, fails to potentiate the hormone respon ... | 1994 | 8117276 |
| wild-type p53 tumor suppressor gene restores differentiation of human squamous carcinoma cells but not the response to transforming growth factor beta. | in order to clarify the role of the p53 tumor suppressor gene in controlling growth and differentiation of human epithelial cells, we transfected a wild-type p53 complementary dna, driven by a dexamethasone-inducible mouse mammary tumor virus promoter, into sqcc/y1 human head-and-neck squamous carcinoma cells. when treated with dexamethasone, 2 of 8 independent clones that contained integrated vector sequences expressed wild-type p53-specific mrna as well as nuclear p53 protein. the highest p53 ... | 1993 | 8117626 |
| genetic control of retroviral disease in aging wild mice. | different populations of wild mice (mus musculus domesticus) in los angeles and ventura counties were observed over their lifespan in captivity for expression of infectious murine leukemia virus (mulv) and murine mammary tumor virus (mmtv) and for the occurrence of cancer and other diseases. in most populations of feral mice these indigenous retroviruses were infrequently expressed and cancer seldom occurred until later in life (> 2 years old). mmtv was found in the milk of about 50% of wild mic ... | 1993 | 8125269 |
| androgens regulate expression of the gene coding for a mouse vas deferens protein related to the aldo-keto reductase superfamily in epithelial cell subcultures. | mouse vas deferens protein (mvdp), a member of the aldo-keto reductase superfamily, is exclusively produced in the vas deferens. to better understand androgen-regulated mvdp gene expression we have used rna hybridization to study the effects of androgens on the steady-state levels of mvdp mrna in vas deferens epithelial cell subcultures. northern blot analysis revealed that these cells only express mvdp mrna in the presence of androgens. there was a close relationship between mvdp mrna levels an ... | 1994 | 8136297 |
| activation of natural killer cells by mouse mammary tumor virus c4 in balb/c and t-cell receptor v beta 2-transgenic mice. | lymphocytic infiltrates of balb/c c4 hyperplastic alveolar nodule (han) have elevated natural killer (nk) activity, which correlates positively with the progression of c4 han to tumor: c4 han produces an infectious mouse mammary tumor virus, mmtv(c4), which encodes a superantigen that activates and deletes t-cells with the v beta 2 segment in the t-cell receptor. in this report, nk activation by both mmtv(c4) and mmtv(c4) superantigen was tested. nk activity was measured in naive balb/c mice, ba ... | 1994 | 8137259 |
| acceleration of mammary neoplasia in transforming growth factor alpha transgenic mice by 7,12-dimethylbenzanthracene. | a mouse mammary tumor virus enhancer/promoter-transforming growth factor alpha transgenic mouse model has been described in which mammary tumors develop (y. matsui et al., cell, 61: 1147-1155, 1990). in line 29, spontaneous mammary tumors do not develop before 300 days of age in virgin females. herein, line 29 virgin females and their nontransgenic littermates have been treated with 7,12-dimethylbenzanthracene (dmba) at varying dosages and times. orogastric instillation of a single dose of dmba ... | 1994 | 8137281 |
| expression and purification of the mouse mammary tumor virus gag-pro transframe protein p30 and characterization of its dutpase activity. | the mouse mammary tumor virus gag-pro transframe protein (p30) contains the nucleocapsid protein domain derived from the 3' end of gag, fused to 154 residues encoded by the 5' region of the pro open reading frame. the dna coding for p30 was cloned into the plasmid palter-1, and an additional nucleotide was inserted by site-directed mutagenesis to allow the read-through from the gag into the pro open reading frame. the obtained insert was then cloned into pgex-2t, a plasmid containing the glutath ... | 1994 | 8139016 |
| levels of viral glycoprotein reflect enhanced effectiveness of combined drug treatments. | a chemosensitivity assay with small replicate mm5mt/cl c3h mammary tumor cell cultures was developed to determine whether changes in viral antigen expression and release into culture fluids could be utilized as an in vitro measure of single and combined drug effect. the measurement of drug concentrations required for identical 50% reductions in viral antigen levels (ed50s) allowed the dosage-dependence of the same drug to be compared alone and in combination drug treatments. the 52,000 mw viral ... | 1994 | 8139377 |
| subversion of host immune responses by viral superantigens. | recent experiments with mouse mammary tumor virus indicate that expression of a virally encoded superantigen by b cells and its subsequent recognition by t cells are essential steps for amplification of infection and virus transmission. preliminary results suggest that superantigens may also be expressed during retroviral infection in humans. | 1993 | 8143113 |
| antiandrogens inhibit human androgen receptor-dependent gene transcription activation in the human prostate cancer cells lncap. | human androgen receptor (har) is a ligand-dependent transcription factor that mediates androgen-induced actions on target tissues. transfection studies in the human prostate cancer cell line lncap examine the ability of dihydrotestosterone (dht), hydroxyflutamide (ho-flu), cyproterone acetate (cypro.a), and ru 23908-10 to stimulate or to inhibit the transcription activation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase (mmtv-cat). dht stimulated transcription activatio ... | 1994 | 8146066 |
| distribution of mouse mammary tumor virus in asian wild mice. | several groups of wild mice (mus musculus) were captured from eight different locations in asia and bred for several generations in a facility free of any laboratory strains of mice carrying mouse mammary tumor virus (mmtv). the distribution of endogenous mmtv proviral sequences in the liver tissues of these mice was investigated by using southern blot hybridizations. four categories of mice were identified. mice originating from bogor, indonesia (cas-bgr); he-mei, taiwan (cas-hmi/1); and malays ... | 1994 | 8151805 |
| transcription of herv-k-related ltrs in human placenta and leukemic cells. | the human genome contains a family of endogenous retroviruses, herv-k, with sequence homology to the b-type mouse mammary tumor virus (mmtv). we have detected herv-k-ltr related cdna clones by screening a human placenta cdna library with a herv-k ltr probe. three of the isolated cdna clones were characterized by nucleotide sequencing. the analyzed clones did not contain any retroviral sequences other than those related to herv-k ltrs, but were found to be coexpressed with cellular sequences. fur ... | 1994 | 8152277 |
| therapeutic progress and comparative aspects in chronic myelogenous leukemia (cml): interferon alpha vs. hydroxyurea vs. busulfan and expression of mmtv-related endogenous retroviral sequences in cml. german cml study group. | in summary, it can be expected that the availability of unrelated donors will increase the number of cml patients that can be treated curatively with allogeneic bmt. hydroxyurea has replaced busulfan as first line treatment in cml since it prolongs survival. ongoing randomized studies comparing ifn-based treatment regimens with standard chemotherapy or ifn-monotherapy probably will answer the question whether ifn can cure a small percentage of cml patients and whether this small percentage can b ... | 1994 | 8152279 |
| pregnancy dependence of mammary tumours in ddd mice congenic for mtv-2, ddd/1-mtv-2/mtv-2. | mammary tumours developed in 110 (95.7%) of 115 ddd/1-mtv-2/mtv-2 (ddd/1-mtv-2) and 24 (47.1%) of 51 ddd/1fddd/1-mtv-2 (ddd/1fmtv-2) force-bred female mice during a one-year period. the mean tumour age +/- se was 220 +/- 7 and 269 +/- 7 days, respectively. these tumours were examined for responsiveness to pregnancies by comparing their growth after transplantation between virgin and breeding recipients. of 73 tumours from ddd/1-mtv-2 mice, 9 (12%) were completely pregnancy-dependent (cpd), 3 (4% ... | 1994 | 8158968 |
| b cells are essential for murine mammary tumor virus transmission, but not for presentation of endogenous superantigens. | murine mammary tumor 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 through milk. here we show that b cell-deficient mice 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 no deletion of mmtv superantigen-reactive t cells ... | 1994 | 8163931 |
| architectural variations of inducible eukaryotic promoters: preset and remodeling chromatin structures. | the dna in a eukaryotic nucleus is packaged into a nucleosome array, punctuated by variations in the regular pattern. the local chromatin structure of inducible genes appears to fall into two categories: preset and remodeling. preset genes are those in which the binding sites for trans-acting factors are accessible (i.e. in a non-nucleosomal, dnase i hypersensitive configuration) prior to activation. in response to the activation signal, positive factors bind to cis-acting regulatory elements an ... | 1994 | 8166669 |
| ancestry of sine-r.c2 a human-specific retroposon. | we have reported previously that a retroposon, containing a variable number of tandemly repeated nucleotide sequences, is present in the third intron of the human c2 gene. this element, termed sine-r.c2, is a member of a large retroposon family derived from the endogenous retrovirus herv-k10 and estimated to include a few thousand copies per haploid human genome. in the present study we analyzed genomic dna from 175 humans from several ethnic groups including americans of european and african de ... | 1994 | 8168832 |
| differential temporal and spatial gene expression of fibroblast growth factor family members during mouse mammary gland development. | mammary gland development is dependent upon local regulatory factors as well as systemic hormones to mediate gland morphogenesis and associated mesenchymal-epithelial interactions. fgf-3 (int-2) has been implicated as an oncogenic growth factor produced locally in mouse mammary tumor virus-induced mammary tumorigenesis. the observation that fgf-3 is not expressed during normal mammary development as well as the high degree of cellular proliferation and angiogenesis that accompany mammary gland g ... | 1994 | 8170478 |
| cause of failure of lactation in mouse mammary tumor virus/human transforming growth factor alpha transgenic mice. | transgenic female mice bearing human transforming growth factor-alpha (tgf alpha) cdna under the control of the mouse mammary tumor virus enhancer/promoter became pregnant but failed lactation. tgf alpha mrna was detected in the mammary glands of these mice by the reverse transcriptase-polymerase chain reaction. by the use of collagenase-dissociated mammary epithelial cells, the binding of prolactin to its receptor was determined before and after parturition. at the end of pregnancy, the binding ... | 1994 | 8171044 |
| identification of thyroid hormone response elements in rodent pcp-2, a developmentally regulated gene of cerebellar purkinje cells. | in a previous study, we have shown that in vivo expression of the cerebellar purkinje cell-specific gene pcp-2 is regulated by thyroid hormone (t3) during neonatal development. in addition, transient cotransfection studies using thyroid hormone receptors (trs) and a pcp-2-lacz construct pointed to direct regulation of pcp-2 gene expression by t3. therefore, we have initiated the following series of studies to define more precisely the location of the thyroid hormone regulatory elements in the pc ... | 1994 | 8175765 |
| maternal transfer of infectious mouse mammary tumor retroviruses does not depend on clonal deletion of superantigen-reactive v beta 14+ t cells. | female c3h/hej mice maternally transmit through their milk an infectious mouse mammary tumor retrovirus (mmtv) which causes clonal deletion of t cell receptor (tcr)v beta 14+ t cells reactive to the retroviral superantigen (sag). to test whether cd4+ or cd8+ t cells are crucial for intestinal infection and maternal transfer of exogenous retroviruses, newborn mice lacking cd4 or cd8 molecules after gene targetting were raised by surrogate c3h/hej mothers. in cd8-/- mice, clonal deletion of tcrv b ... | 1994 | 8181521 |
| mammary tumorigenesis and metastasis in transgenic mice. | the transgenic mouse has emerged as an important model system to assess the transforming potential of oncogenes in the mammary epithelium. mammary gland-specific expression of oncogenes in transgenic mice has resulted in the induction of a variety of phenotypes ranging from benign epithelial hyperplasias to metastatic mammary tumors. the induction of tumors in most of these transgenic models is a multi-step process where transgene expression, although required, is not sufficient for conversion o ... | 1994 | 8186390 |
| the impact of 5'-cg-3' methylation on the activity of different eukaryotic promoters: a comparative study. | the inhibiting or inactivating effects of position-specific promoter methylation in different viral or human cellular promoters ad2 e2al, sv40, ltr-mmtv, hsv-tk, tnf alpha) have been compared by in vitro 5'-ccgg-3' methylation by m-hpaii or the m-sssi dna-methyltransferase, respectively. in most promoters, 5'-cg-3' methylation reduces activity to a few percent of that of mock-methylated controls. the number of 5'-cg-3' dinucleotides in a promoter does not strictly correlate with the extent of me ... | 1994 | 8187893 |
| two glucose-signaling pathways in s14 gene transcription in primary hepatocytes: a common role of protein phosphorylation. | transcription of the rat s14 gene is induced in response to increased carbohydrate metabolism in the liver. because carbohydrate-induced changes in lipogenesis are mediated in part by changes in phosphorylation of multiple proteins, we investigated the role of protein phosphorylation on transcriptional regulation of the two carbohydrate response elements, a thyroid hormone receptor-independent carbohydrate response element and a thyroid receptor-dependent glucose response element located up-stre ... | 1994 | 8194479 |
| superantigens and retroviral infection: insights from mouse mammary tumor virus. | superantigens induce a vigorous immune response by stimulating t cells that express particular t-cell receptor v beta chains. mouse mammary tumor virus is a milk-transmitted retrovirus that encodes such a superantigen. paradoxically, as discussed by werner held and colleagues, the strong superantigen-induced immune response permits the survival of the virus via t-cell dependent clonal expansion of infected b cells. | 1994 | 8198710 |
| on the generation of diversity in endogenous superantigens. | | 1994 | 8198711 |
| [superantigens]. | | 1994 | 8202838 |
| mammary hyperplasia and carcinoma in mmtv-cyclin d1 transgenic mice. | physical associations between cyclins, viral oncogenes and tumour suppressor genes imply a central role for cyclins in growth control. cyclin d1 was identified as a candidate oncogene (prad1) in tumour-specific dna rearrangements and is suspected to be a contributor to several types of neoplasms including breast cancer. cyclin d1 also rescues g1 cyclin-defective saccharomyces cerevisiae, and is a growth-regulated gene. despite evidence suggesting that cyclin d1 is an oncogene, its ability to tra ... | 1994 | 8208295 |
| spontaneous and inducible epidermal hyperplasia in transgenic mice expressing hiv-1 nef. | the pathophysiological consequence of hiv-1 nef gene expression was investigated in transgenic mice carrying a cdna for nef linked to either the hiv-1 ltr or the mmtv ltr. in hiv/nef transgenic mouse lines, nef expression was detected exclusively in the skin and a significant fraction of hiv/nef transgenic animals (30-75%, depending on the line) spontaneously developed discrete proliferative skin lesions resembling papillomas that were often accompanied by a progressive ulceration of the epiderm ... | 1993 | 8212579 |
| steroid hormone receptors: interaction with deoxyribonucleic acid and transcription factors. | gene regulation by steroid hormones is mediated by binding of the hormone ligand to the corresponding receptor that triggers a complex set of interactions of the hormone receptors with each other, with dna in chromatin, and with a variety of other proteins. in this review we attempt to summarize what is known about these interactions using as the main example the regulation of mouse mammary tumor virus transcription by glucocorticoids and progestins. we describe in some detail the interaction of ... | 1993 | 8223341 |
| identification of an endogenous mammary tumor virus involved in the clonal deletion of v beta 2 t cells. | expression of v beta (beta-chain variable region) gene segments was investigated in the mus m. domesticus ddo strain, which possesses a large genomic deletion encompassing 20 of the 29 v beta gene segments known in balb/c. stainings using v beta-specific monoclonal antibodies revealed that up to 60% of the peripheral t cells use 3 v beta gene segments. variable frequencies of v beta 2 t cells were observed among ddo individuals. segregation analyses of f2 crosses between v beta 2-deletor mice an ... | 1993 | 8223851 |
| a new infectious mammary tumor virus in the milk of mice implanted with c4 hyperplastic alveolar nodules. | we have previously characterized an infectious mouse mammary tumor virus [(mmtv(sw)] which induces a strong superantigen response in vivo. here we describe the isolation and characterization of mmtv(c4) which was derived from milk of mice implanted with hyperplastic alveolar nodules. mmtv(c4) stimulates v beta 2 expressing t cells after local injection in vivo. comparison with known open reading frame (orf) sequences revealed high homology to mtv-6, an endogenous virus interacting with v beta 3- ... | 1993 | 8223852 |
| interplay between superantigens and the immune system. | superantigens interact with the immune system by binding to major histocompatibility complex (mhc) class ii proteins and activating t cells through the variable region of the t cell receptor beta-chain. through this means they can cause massive proliferation and then death of a large proportion of t cells. superantigens are produced by bacteria, mycoplasmas, retroviruses, and probably by other organisms. in some cases, the superantigen is crucial to the organism's life cycle. mouse mammary tumor ... | 1993 | 8228628 |
| mouse mammary tumor virus-induced tumorigenesis in sag transgenic mice: a laboratory model of natural selection. | transgenic mice that expressed the superantigen protein encoded in the c3h exogenous mouse mammary tumor virus long terminal repeat deleted their v beta 14+ t cells during the shaping of their immune repertoire and showed no evidence of virus production in their mammary glands after infection by milk-borne c3h exogenous virus. however, they developed mammary gland tumors that had newly integrated copies of c3h exogenous virus, although the latency of tumor formation was much longer than in their ... | 1993 | 8230492 |
| the 3' half of the mouse mammary tumor virus orf gene is not sufficient for its superantigen function in transgenic mice. | the mouse mammary tumor virus (mmtv) long terminal repeat contains an open reading frame (orf) of 960 nucleotides encoding a 36 kda polypeptide with a putative transmembrane domain and five n-glycosylation sites in the n-terminal part of the protein. transgenic mice bearing either the complete or the 3' terminal half of the orf sequence of mmtv-gr under the control of the sv40 promoter were raised. as shown previously by facs analysis transgenic mice which express the complete orf gene have a si ... | 1993 | 8232325 |
| endogenous superantigens: tools for dissecting t-cell repertoire selection. | | 1993 | 8235041 |
| superantigens. | | 1993 | 8235044 |
| mouse mammary tumor virus-mediated t-cell receptor negative selection in hla-dra transgenic mice. | products of specific mouse mtv genes expressed in association with mouse mhc class ii products cause the deletion of t cells expressing particular tcr v beta gene segments. these endogenous deletion ligands have been termed superantigens due to their ability to negatively select entire t-cell families, as defined by v beta-chain usage. in most cases, deletion is preferentially effected through interaction of the mtv ligand with h-2e products. although human dr alpha shares only 75% identity with ... | 1993 | 8244778 |
| elevated levels of cyclin d1 protein in response to increased expression of eukaryotic initiation factor 4e. | cyclin d1 is a g1-specific cyclin that has been linked to lymphoid, parathyroid, and breast tumors. recent studies suggested that high protein levels of cyclin d1 are not always produced when cyclin d1 mrna is overexpressed in transfected cells, suggesting that posttranscriptional events may be important in cyclin d1 regulation. the mrna cap-binding protein (eukaryotic initiation factor 4e [eif-4e]) is a potential regulatory of several posttranscriptional events, and it can itself induce neoplas ... | 1993 | 8246956 |
| activation of the mouse mdr3 gene by insertion of retroviruses in multidrug-resistant p388 tumor cells. | in multidrug-resistant (mdr) derivatives of the mouse lymphoid tumor p388, the emergence of mdr is associated with overexpression and transcriptional activation of the mdr3 gene, either in the absence of (p388/vcr-10) or concomitant with (p388/adm-2) gene amplification. in both instances, northern (rna) blotting analyses have suggested the presence of altered mdr3 transcripts in these cells, possibly originating from novel transcription initiation sites. the mechanisms underlying mdr3 overexpres ... | 1993 | 8246958 |
| newly expressed progesterone receptor cannot activate stable, replicated mouse mammary tumor virus templates but acquires transactivation potential upon continuous expression. | during development and differentiation, the expression of transcription factors is regulated in a temporal fashion. newly expressed transcription factors must interact productively with target genes organized in chromatin. although the mechanisms governing factor binding to chromatin templates are not well understood, it is now clear that template access can be dramatically influenced by nucleoprotein structure. we have examined the ability of a well characterized transactivator, the progesteron ... | 1993 | 8248228 |
| growth of the mammary gland in rhino mouse. | the rhino mouse, so called because of its characteristic rhinocerous-like skin cannot raise its young. although the animal has rudimentary mammary glands, these are thought to be defective due to their impossibility to raise their young. morphological observations of the female mammary glands of rhino mice (hrrh/hrrh) were carried out and the results were compared with those of their normal litter mates (hrrh/+) at various ages from 1 month to 1 year. no morphological differences in mammary glan ... | 1993 | 8253147 |
| inhibition of mammary duct development but not alveolar outgrowth during pregnancy in transgenic mice expressing active tgf-beta 1. | the transforming growth factors beta (tgfs-beta) are potent inhibitors of cell proliferation and are usually secreted in a latent form. tgf-beta 1, tgf-beta 2, and tgf-beta 3 are expressed in distinct but overlapping patterns in the developing mouse mammary gland. to study the role of transforming growth factor-beta 1 (tgf-beta 1) in normal mammary development and in mammary neoplasia, we have constructed three transgenic mouse lines that express a simian tgf-beta 1 s223/225 mutated to produce a ... | 1993 | 8253379 |
| the adenovirus-mediated delivery of a reporter gene permits the assessment of androgen receptor function in genital skin fibroblast cultures. stimulation of gs and inhibition of g(o). | defects in the androgen receptor cause a spectrum of abnormalities in genetic males ranging from phenotypic women with testicular feminization to men with minor defects in fertility and/or virilization. the diagnosis of androgen resistance can be quite cumbersome, including analysis of the family history, karyotyping, endocrine studies, measurement of androgen binding in genital skin fibroblasts, and, in some instances, sequencing of mutant cdnas. furthermore, androgen-binding studies may be nor ... | 1993 | 8253718 |
| identification of two v beta 7-specific viral superantigens. | the commonly used strains of laboratory mice have mouse mammary tumor viruses (mtv) integrated at various locations in their dna. the number and position of these integrants varies from one strain of mouse to another. it has recently been shown that the genomes of many of the mtv code for superantigens. the predicted amino acid sequences of these superantigens and their specificity for tcr v beta differs for each mtv integrant. this study contains the predicted amino acid sequence and v beta spe ... | 1994 | 8254207 |
| functional redundancy of octamer elements in the mouse mammary tumor virus promoter. | the promoter of mouse mammary tumor virus contains three overlapping sequence elements related to the octamer consensus (atgcaaat) that are largely contained within two 10 bp direct repeats (cttatgtaaa) separated by a 2 bp spacer between 60 and 39 relative to the start of transcription. gel electrophoresis mobility shift competition assays demonstrate that the most distal of these octamer-related elements is recognized by a protein that also binds to the most proximal element, while the central ... | 1993 | 8255781 |
| nucleosome-mediated disruption of transcription factor-chromatin initiation complexes at the mouse mammary tumor virus long terminal repeat in vivo. | glucocorticoid induction of mouse mammary tumor virus (mmtv) is short lived, returning to base levels within 24 h despite the continued presence of hormone. mmtv dna sequences assembled as chromatin require hormone for binding by nuclear factor 1 (nf1) and octamer proteins (oct). however, in the same cells, nf1 and oct factors are bound to transiently introduced dna in the absence of hormone. in contrast, recruitment of the tata-binding protein and a novel dna-binding protein, which we have desi ... | 1994 | 8264599 |
| preferential repair of uv damage in highly transcribed dna diminishes uv-induced intrachromosomal recombination in mammalian cells. | the relationships among transcription, recombination, dna damage, and repair in mammalian cells were investigated. we monitored the effects of transcription on uv-induced intrachromosomal recombination between neomycin repeats including a promoterless allele and an inducible heteroallele regulated by the mouse mammary tumor virus promoter. although transcription and uv light separately stimulated recombination, increasing transcription levels reduced uv-induced recombination. preferential repair ... | 1994 | 8264606 |
| human progesterone receptor a form is a cell- and promoter-specific repressor of human progesterone receptor b function. | two distinct isoforms of the human progesterone receptor (hpr-a and hpr-b) have been identified previously. they differ only in that hpr-b contains an additional 164 amino acids at the amino terminus. among various species these two forms arise as a result of either alternate initiation of translation from the same mrna or by transcription from alternate promoters within the same gene. in order to understand the reason for their existence, we studied the transcriptional capacity of these individ ... | 1993 | 8264658 |
| comparison of expression of a series of mammalian vector promoters in the neuronal cell lines pc12 and ht4. | | 1993 | 8267961 |
| rat t cell response to superantigens. i. v beta-restricted clonal deletion of rat t cells differentiating in rat-->mouse chimeras. | t cells of mice display v beta-specific reactivity for a spectrum of mouse mammary tumor virus (mtv) antigens; confrontation with these antigens during ontogeny causes substantial "holes" in the t cell repertoire. since endogenous mtv antigens are rare in other species, the question arises whether v beta-specific recognition of mtv antigens is unique to mice. to examine this question, rat t cells were allowed to differentiate from stem cells in severe combined immunodeficiency (scid) mice. these ... | 1994 | 8270883 |
| rat t cell responses to superantigens. ii. allelic differences in v beta 8.2 and v beta 8.5 beta chains determine responsiveness to staphylococcal enterotoxin b and mouse mammary tumor virus-encoded products. | the previous paper in this series demonstrates that rat t cells developing de novo in the presence of mouse mammary tumor virus (mtv) antigens in rat-->severe combined immunodeficiency (scid) mouse xenochimeras display a distinct pattern of v beta-restricted deletion; this deletion pattern is remarkably similar to that occurring during thymic development of mouse t cells in mtv+ strains. in addition, t cells developing in the absence of mtv antigens in these rat-->mouse xenochimeras are tolerant ... | 1994 | 8270884 |
| interaction of antiandrogen-androgen receptor complexes with dna and transcription activation. | human androgen receptor (har) is a ligand-dependent transcription factor that mediates androgen-induced actions on target tissues. transfection studies in receptor deficient monkey kidney cells cv-1 in culture examine the ability of dihydrotestosterone (dht) and of the antiandrogens hydroxylflutamide (ho-flu), cyproterone acetate (cypro.a) and ru 23908-10 to stimulate or to inhibit the transcription activation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase (mmtv-cat). c ... | 1993 | 8274404 |
| chromatin structure modulates transcription factor binding to the mouse mammary tumor virus (mmtv) promoter. | the mmtv promoter contains a complex hormone responsive region (hrr) upstream of a binding site for the transcription factor nuclear factor i (nfi). hormonal induction of mmtv expression requires the integrity of both the hrr and the nfi binding site. however, in vitro nfi acts as a basal transcription factor on the mmtv promoter that does not cooperate but rather competes with the hormone receptors in terms of binding to mmtv-dna. fragments that contain the hrr and the nfi binding site have bee ... | 1993 | 8274422 |
| glucocorticoid receptor conversion to high affinity nuclear binding and transcription enhancement activity in chinese hamster ovary cells subjected to heat and chemical stress. | the untransformed glucocorticoid receptor (gr) is a heteromeric complex containing two molecules of the 90-kda heat shock protein (hsp90) and one molecule of the 56-kda heat shock protein (hsp56). in the absence of hormone, this complex is found in the cytosolic fraction of cells, and upon hormone-binding the complex dissociates and the gr is recovered in the nuclear pellet fraction. given the association of heat shock proteins with the cytosolic form of the gr, we have examined the effects of h ... | 1993 | 8274442 |
| prolactin acts on the extreme 5' portion of mmtv ltr involving a mammary cell-specific enhancer. | we have previously shown that a human mammotropic polypeptide hormone, prolactin (prl) can act synergistically with steroid hormones to regulate gene expression directed by the long terminal repeat of mouse mammary tumor virus (mmtv ltr) in a human ductal carcinoma cell line t47d cells using a chloramphenicol acetyltransferase reporter gene system and gene transfection methods. in the present study, using various recombinant plasmids we analyzed functional elements in the mmtv ltr that is essent ... | 1993 | 8276123 |
| lactogenic hormones and extracellular matrix regulate expression of igf-1 linked to mmtv-ltr in mammary epithelial cells. | the cell line md-igf-1, containing an ovine igf-1 cdna driven by the mouse mammary tumor virus-long terminal repeat (mmtv-ltr) promoter, was used to study expression of igf-1 linked to the mmtv-ltr in bovine mammary epithelial cells in response to various hormonal and substratum stimuli. acute sensitivity of the mmtv-ltr promoter to glucocorticoids and sex steroids was ascertained by transient transfection of parental mac-t cells with an mmtv-cat construct. specifically, cat activity was induced ... | 1993 | 8276130 |
| mammary tumour induction by pituitary grafting in male mice: an animal model for male breast cancer. | isologous anterior pituitary grafting, 4 each, to 3-4-month-old shn and sln male mice resulted in an appearance of mammary tumours from 8 months of age and the incidence at 12 months reached 53.8% in each strain. all tumours were diagnosed as type b adenocarcinomas. in association with the results, normal mammary gland growth and mouse mammary tumour virus (mmtv)-gp52 antigen levels in the submaxillary glands were stimulated by the treatment in these strains. the effect of pituitary grafting was ... | 1993 | 8277709 |
| frequent mutations in breast cancer. | | 1993 | 8279759 |
| repression of glucocorticoid receptor function by the anti-rheumatic gold compound aurothiomalate. | we describe functional interaction between the anti-rheumatic water-soluble gold compound aurothiomalate and glucocorticoid receptors. aurothiomalate contains gold in the au(i) state, and au(i) alone, not thiomalate or malate, reduced the ligand-binding activity of the glucocorticoid receptor. au(i) also interfered with the productive interaction between the glucocorticoid receptor and the cognate target dna sequences and repressed the transactivation function of the receptor. thus, au(i) variab ... | 1993 | 8280129 |
| effect of sv40 and mmtv promoters on intermolecular homologous recombination in rat cells. | the effect of sv40 and mmtv promoters on intermolecular homologous recombination between neomycin (neo) genes carrying deletions proximal and distal to the promoters has been examined in rat xc cells. one deleted neo gene linked to either promoter and the other deleted one without any promoter were co-transfected to cells so that the number of resulting g418-resistant colonies reflected the frequency at which the promoter-linked neo allele had been corrected by homologous recombination. we found ... | 1993 | 8280133 |
| assembly of glucocorticoid receptor and c-jun homodimer on the promoter of mouse mammary tumor virus-long terminal repeat is influenced by order of addition. | interactions between the glucocorticoid receptor (gr) and c-jun/c-jun homodimer (jun) on the promoter dna of mouse mammary tumor virus-long terminal repeat (mmtv-ltr) are reported here using the electrophoretic mobility shift assay (emsa). both gr and jun are capable of independently binding to their respective response elements, including glucocorticoid response element (gre) and phorbol ester response element (tre), on mmtv-ltr promoter. the protein-dna complex, assembled by pre-incubating jun ... | 1993 | 8280142 |
| pharmacological and functional characterization of human mineralocorticoid and glucocorticoid receptor ligands. | we characterized the pharmacological profiles of the human mineralocorticoid and glucocorticoid receptor for 11 natural and synthetic steroids regarding binding pharmacology, intracellular localization of hormone-receptor complexes, and agonistic or antagonistic properties at the gene expression level. the sex steroid progesterone bound with an affinity (ki < 0.01 nm) even higher than that of aldosterone to the human mineralocorticoid receptor and effectively antagonized the effect of aldosteron ... | 1993 | 8282004 |
| lipids alter the level and distribution of mouse mammary tumor virus gp52 in vitro. | linoleic acid, cholesterol, dexamethasone and progesterone were tested by immunocytochemistry and immunoprecipitation for their single and combined effects in vitro on mouse mammary tumor virus (mmtv) gp52 distribution among three compartments: cell-associated antigen, extracellular virus particles and extracellular shed antigen unassociated with virus particles. results indicated that all additives significantly increased total mmtv gp52 levels and altered the distribution. linoleic acid and de ... | 1993 | 8287372 |
| genomic distribution and transcription of solitary herv-k ltrs. | the human genome contains a family of endogenous retroviruses, herv-k, with sequence homology to the b-type mouse mammary tumor virus. we have now identified a single herv-k ltr within the c-type-related human retroviral element s71. the herv-k ltr is located in the antisense direction between the s71 gag and the pol gene, replacing the 5' half of s71 pol. a number of herv-k ltr-related cdna clones were detected by screening various human cdna libraries with an s71 herv-k ltr probe, indicating a ... | 1993 | 8288228 |
| repression of mouse mammary tumor virus transcription by a transcription factor complex. binding of individual components to separated dna strands. | expression of mouse mammary tumor virus in t lymphocytes appears to be required for accession of horizontally transmitted virus to the mammary gland. further, deletions in the long terminal repeat which relax constraints on viral transcription promote t cell lymphoma. we have identified a polypurine transcriptional repressor element (nre1) that is deleted from viruses that induce t cell lymphoma. nre1 binding activity in nuclear extracts proved to be related to a growth inhibitory activity that ... | 1994 | 8288611 |
| stably integrated mouse mammary tumor virus long terminal repeat dna requires the octamer motifs for basal promoter activity. | in the mouse mammary tumor virus promoter, a tandem of octamer motifs, recognized by ubiquitous and tissue-restricted oct transcription factors, is located upstream of the tata box and next to a binding site for the transcription factor nuclear factor i (nf-i). their function was investigated with mutant long terminal repeats under different transfection conditions in mouse ltk- cells and quantitative s1 nuclease mapping of the transcripts. in stable transfectants, which are most representative ... | 1994 | 8289800 |
| physical association and functional antagonism between the p65 subunit of transcription factor nf-kappa b and the glucocorticoid receptor. | glucocorticoids, which are widely used as antiinflammatory agents, downregulate the expression of the interleukin 6 gene and of additional cytokine genes involved in inflammatory responses. conversely, the transcription factor nf-kappa b, a member of the rel family of transcription factors, has been implicated in the induction of multiple genes involved in the early processes of immune and inflammatory responses. this prompted us to investigate whether one of the mechanisms by which glucocortico ... | 1994 | 8290595 |
| progression of androgen-sensitive mouse tumor (shionogi carcinoma 115) to androgen-insensitive tumor after long-term removal of testosterone. | shionogi carcinoma 115 (sc115) is an androgen-sensitive transplantable mouse tumor. to study the mode of progression from androgen-sensitive to -insensitive tumor, cloned sc115 cells were serially cultured without androgen. shortly after withdrawal of androgen, sc115 cells showed markedly decreased growth, but growth resumed gradually with loss of response to androgen and the cells 60 weeks after androgen removal [a(-)60 cells] grew faster than sc115 cells cultured in the presence of androgen. a ... | 1993 | 8294220 |
| the mouse mammary tumor virus envelope gene product is required for superantigen presentation to t cells. | transgenic mice expressing either the mouse mammary tumor virus (mmtv) superantigen gene (sag) alone or in combination with the viral envelope genes (env) (lel), or all of the viral genes (gag, pol, env, and sag) (hyb pro), deleted v beta 14+ t cells from their immune repertoire. however, only lel or hyb pro transgenic antigen-presenting cells were capable of stimulating a proliferative response from nontransgenic primary t cells or interleukin 2 production from a v beta 15-bearing t cell hybrid ... | 1994 | 8294859 |
| delay in expression of a mammary tumor provirus is responsible for defective clonal deletion during postnatal period. | a gene-encoding ligand for deletion of t cells bearing tcrv beta 6 and v beta 8.1 cosegregates a new mammary tumor provirus locus, mtv-50 in nc mice. the sequence of the open reading frame (orf) in the 3' long terminal repeat (ltr) of mtv-50 was strikingly similar to those of mtv-7, mtv-43 and exogenous mouse mammary tumor virus (sw) with properties of minor lymphocyte stimulating antigen 1a. consistent with previous reports, clonal deletion of mature thymocytes bearing tcrv beta 6 was defective ... | 1994 | 8299700 |
| tissue-specific expression of messenger rnas encoding endogenous viral superantigens. | the minor lymphocyte stimulating (mls) superantigens of mice are encoded by open reading frames (orfs) in the 3' long terminal repeats (ltrs) of endogenous mouse mammary tumor viruses. by stimulating all t cells bearing particular tcr v beta proteins, these viral superantigens (v-sags) exert profound effects on t cell development and function. we have examined expression of the 1.7 kb mrna product predicted to encode v-sag proteins in different cells and tissues of the immune system. the ltr-orf ... | 1994 | 8301115 |
| expression of mtv-7 sag gene in vivo using a retroviral vector results in selective inactivation of superantigen reactive t cells. | t cells expressing specific tcr v beta chains are intrathymically eliminated in mice expressing the murine mls (minor lymphocyte stimulating) superantigens. recently, in vitro studies have shown that the endogenous mouse mammary tumor virus (mmtv)-7 sag gene encodes mls-1 ag. the demonstrated ability of mmtv superantigen proteins to react with tcrs has led to the postulate that other infectious retroviruses may use superantigen-like molecules to modify the host's immune system. in this report, s ... | 1994 | 8301116 |
| exogenous mtv-7 superantigen transgene expression in major histocompatibility complex class ii i-e- mice reconstituted with embryonic stem cell-derived hematopoietic stem cells. | direct genetic manipulation of hematopoietic cells is limited by the lack of an established hematopoietic stem cell line. it has been demonstrated that embryonic stem (es) cell<-->tetraploid embryos are completely es cell-derived and that fetal liver (fl) cells from these embryos support hematopoiesis in lethally irradiated recipients. in this report, we demonstrate that fl cells from es cell<-->tetraploid embryos support normal lymphopoiesis and t-cell repertoire development. moreover, the intr ... | 1994 | 8302843 |
| mls-1 and mls-2 superantigens do not control susceptibility to collagen-induced arthritis in hi and hii mice. | the hi mouse line is sensitive to collagen-induced arthritis (cia), whereas hii is refractory, although both express the h-2q permissive haplotype. the two lines also share the same t-cell receptor (tcr) gene haplotypes for alpha and beta chains. the distribution of mouse mammary tumour viruses (mmtv), which encode endogenous superantigens (sag) such as minor leucocyte-stimulating antigens (mls) known to modulate the available tcr-v beta repertoire, was investigated in the two lines. mls-1 is pr ... | 1993 | 8307618 |
| mvm(p) ns-2 protein expression is required with ns-1 for maximal cytotoxicity in human transformed cells. | the parvovirus-encoded nonstructural (ns) proteins have been implicated in the cytopathogenicity of these agents. although protein ns-1 of minute virus of mice (mvm) has been shown to be toxic, little is known about the role of ns-2 in this process. in order to determine the contribution of ns-1 and ns-2 to cytotoxicity, we took advantage of an expression system controlled by the mouse mammary tumor virus promoter which responds to glucocorticoid stimulation and which controls the expression of ... | 1993 | 8317090 |
| superantigens as immunogens and tolerogens. | superantigens are a family of proteins that are receiving a great deal of attention as a group of potent immunomodulatory molecules. they combine with mhc class ii molecules to form the ligands that stimulate t cells via the v beta element of the t cell receptor. two groups of superantigens have been described: those expressed endogenously such as the mouse mammary tumour virus (mmtv) and the exogenously derived products such as the staphylococcal enterotoxins. here we review the interactions be ... | 1993 | 8324944 |
| the steroid antagonist ru486 exerts different effects on the glucocorticoid and progesterone receptors. | to determine whether the steroid antagonist ru486 mediates its antiglucocorticoid and antiprogestin activities by the same or different receptor mechanisms, a direct comparison of ru486 interaction with glucocorticoid (gr) and progesterone (pr) receptors was made. the effects of ru486 on transformation of gr and pr 8-10s complexes in the intact cell and in vitro were analyzed by sucrose density gradient centrifugation, and the in vitro stability of receptor-heat shock protein-90 interactions was ... | 1993 | 8344212 |
| differential regulation of human progesterone receptor a and b form-mediated trans-activation by phosphorylation. | hormone-dependent phosphorylation of progesterone receptors (prs) plays a functional role in their transcriptional activity. however, hormone-independent phosphorylation has also been shown to modulate the chicken pr-mediated trans-activation in the presence of phosphorylating agents. the present study was designed to investigate the effects of protein kinase a- and protein kinase c-mediated signal transduction pathways on the regulation of the activity of the two forms of human pr (hpra and hpr ... | 1993 | 8365365 |
| moloney murine leukemia virus protease: bacterial expression and characterization of the purified enzyme. | the moloney murine leukemia virus (mo-mulv) protease has been cloned into the prokaryotic expression vector pgex-2t, expressed in fusion with the glutathione s-transferase from schistosoma japonicum, and purified to apparent homogeneity after thrombin cleavage of the chimeric protein. the purified protease showed maximum activity at ph 6.0 and was inhibited by several aspartyl protease inhibitors, found to be active toward the human immunodeficiency virus-1 (hiv-1) protease. peptides representin ... | 1993 | 8372434 |
| a mouse mammary tumor virus promoter element near the transcription initiation site. | transcription from the promoter of mouse mammary tumor virus is subject to both positive and negative control by cellular factors, and proviral promoter elements that mediate a basal level of transcription must in some way respond to these cellular regulatory signals. several such elements, including a tata box, a region containing three octamer-related sequences, and a binding site for nuclear factor 1, have been previously defined. additional promoter mutations have allowed a fourth basal prom ... | 1993 | 8380087 |