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an endogenous retrovirus mediating deletion of alpha beta t cells?a special class of self-antigens (endogenous superantigens) is capable of deleting many murine t cells on the basis of their expression of particular t-cell receptor v beta gene segments. in mice that endogenously express these antigens, tolerance is mediated in part by the clonal deletion of the relevant v beta-bearing t cells. the deletion of i-e-reactive v beta 5.2-bearing t cells is dependent on the coexpression of an i-e tolerogenic coligand (etc)14 and the gene for one of these coligands, ...19911846949
genes encoding ligands for deletion of v beta 11 t cells cosegregate with mammary tumour virus genomes.the t-cell receptor (tcr) repertoire is selected in the thymus after rearrangement of genes encoding tcr alpha and beta chains. selection is based on the recognition by newly emergent t cells of self-ligands associated with molecules of the major histocompatibility complex: some combinations result in positive selection, others in negative selection. negative selection, or clonal deletion, is an important mechanism for eliminating autoreactive t cells. a group of self-ligands involved in clonal ...19911846950
binary system for regulating transgene expression in mice: targeting int-2 gene expression with yeast gal4/uas control elements.we have developed a binary transgenic system that activates an otherwise silent transgene in the progeny of a simple genetic cross. the system consists of two types of transgenic mouse strains, targets and transactivators. a target strain bears a transgene controlled by yeast regulatory sequences (uas) that respond only to the yeast transcriptional activator gal4. a transactivator strain expresses an active gal4 gene that can be driven by any selected promoter. the current paradigm uses the muri ...19911846961
expression of endogenous mtv provirus transcripts in balb/c splenic lymphocytes.the presence of antigen(s) related to the exogenous milk-transmitted murine mammary tumor virus on the surface of balb/c splenic lymphocytes has been documented previously. since the balb/c strain lacks murine mammary tumor virus, the presence of murine mammary tumor virus-related antigen(s) on lymphocytes has been ascribed to expression of germinally transmitted mtv transcripts and proviruses were characterized to evaluate this hypothesis. transcripts from genomic size mtv provirus(es) accumula ...19911847745
mos-induced inhibition of glucocorticoid receptor function is mediated by fos.activation of glucocorticoid hormone-dependent transcription involves the binding of the glucocorticoid hormone to its receptor followed by a specific interaction of the hormone/receptor complex with glucocorticoid responsive elements in the promoter region of hormone-inducible genes. in stably transfected nih3t3 cells expressing the oncogene product of v-mos or fos, the expression from two glucocorticoid responsive promoters, mmtv ltr and metallothionein iia (mtiia), was shown to be impaired an ...19911847998
a frame-shift mutation in the androgen receptor gene causes complete androgen insensitivity in the testicular-feminized mouse.the testicular feminized (tfm) mouse lacks completely androgen responsiveness; and therefore, is unique for studying the role of androgenic steroids in different biological processes. in order to understand the molecular basis of this mutation, 2.8 kilobases of cdna encoding the tfm mouse androgen receptor (ar) were amplified with a polymerase chain reaction (pcr) technique. no large deletion in the coding region of the tfm mouse ar was detected. however, sequence analysis revealed a single base ...19912041777
clonal deletion of v beta 14-bearing t cells in mice transgenic for mammary tumour virus.autoreactive t lymphocytes are clonally deleted during maturation in the thymus. deletion of t cells expressing particular receptor v beta elements is controlled by poorly defined autosomal dominant genes. a gene has now been identified by expression of transgenes in mice which causes deletion of v beta 14+ t cells. the gene lies in the open reading frame of the long terminal repeat of the mouse mammary tumour virus.19911848685
incomplete proviral genome of mouse mammary tumour virus is present on chromosome y of nih swiss and some genetically related mouse strains.an incomplete proviral genome of endogenous mammary tumour virus (mmtv) was found in dna of several strains of mice. this mmtv-related sequence was assigned to the y chromosome since it was clearly observed in male mice only. this mmtv provirus contained a sequence related to ltr (long terminal repeat), but not to gag-pol and env genes. nfs, nih swiss/s, sts/a, and dd/tbr mice have this sequence but balb/chea, shn, sln, c57bl/6njcl, c3h/henjcl and cba/jjcl mice are negative. in the strains conta ...19911849209
neither the endogenous nor a functional steroid hormone receptor binding site transactivate the ribosomal rna gene promoter in vitro.the mammalian ribosomal rna gene promoters exhibit a conserved sequence between positions +1 and +16 that shows a high degree of homology to the response element for glucocorticoids and progestins (gre/pre). these sequences bind specifically the glucocorticoid receptor and the progesterone receptor (pr) albeit with lower affinity than a canonical gre/pre. because steroid hormones are known to affect expression of the ribosomal genes, we tested the influence of hormone receptors on the activity o ...19911911432
glucocorticoid growth suppression response in 13762nf adenocarcinoma-derived con8 rat mammary tumor cells is mediated by dominant trans-acting factors.the in vitro and in vivo growth of con8 cells, a single cell-derived subclone of the 13762nf-transplantable rat mammary adenocarcinoma, is strongly suppressed by glucocorticoid hormones. hybrids were formed between glucocorticoid-suppressible con8.hd6 mammary tumor cells (con8 transfected with the histidinol dehydrogenase selectable marker) and either glucocorticoid-resistant 8ruv7 mammary tumor cells (derived from con8) or mct-htc rat hepatoma cells. both of the glucocorticoid-resistant 8ruv7 a ...19911933866
evaluation of the role of ligand and thermal activation of specific dna binding by in vitro synthesized human glucocorticoid receptor.we have used a dna-binding/immunoprecipitation assay to analyze the capacity of human glucocorticoid receptor (hgr), generated in rabbit reticulocyte lysates, to bind dna. in vitro translated hgr was indistinguishable from native hgr, as determined by migration on sodium dodecyl sulfate-polyacrylamide gels, sedimentation on sucrose density gradients, and reactivity with antipeptide antibodies generated against hgr. in addition, cell-free synthesized hgr was capable of specific binding to glucoco ...19911944294
selective depletion in hiv infection of t cells that bear specific t cell receptor v beta sequences.the mechanism of t cell depletion during infection with the human immunodeficiency virus (hiv) is unclear. examination of the repertoire of t cell receptor v (variable) regions in persons infected with hiv revealed the absence of a common set of v beta regions, whereas v alpha usage was normal. the lack of these v beta segments did not appear to correlate with opportunistic infections. the selective elimination of t cells that express a defined set of v beta sequences may indicate the presence o ...19911948066
establishment and characterization of immortalized non-transplantable mouse mammary cell lines cloned from a mmtv-induced tumor cell line cultured for a long duration.during the culturing of a mouse mammary tumor cell line, mumt73, maintained in vitro for more than a decade, we found morphological heterogeneity in its cells; some showed contact inhibition in their growth, some formed domes and some grew criss cross and piled up. in trying to clone the cell line to isolate cells showing contact inhibition or dome formation, we were able to establish six clonal cell lines. these six cell lines were categorically divided into three groups according to their phen ...19911666666
oncogenes and breast cancer progression. 19911667570
identification and characterization of differentially expressed genes in tumor metastasis: the nm23 gene. 19911667573
functional abnormality of glucocorticoid receptor in shionogi carcinoma 115 cells as evidenced by gene transfer experiments.the assay systems for steroid receptor functions in steroid-sensitive cells (sc-3 cells) were developed in which hormone-responsive element linked to a reporter gene [chloramphenicol acetyl transferase (cat) gene] was transfected by the electroporation technique. stimulation with androgen of sc-3 cells transfected with mouse mammary tumor virus promoter-cat gene (mmtv-cat) resulted in clear enhancement of cat activity, whereas glucocorticoid required abnormally high concentrations to obtain sign ...19911645588
in vitro cleavage of an n-ras messenger-like rna by a ribozyme.a cdna library was constructed in lambda gt10 from t-15 cells, a transformed mouse fibroblast line. the transforming n-ras sequence was recovered and subsequently used as a substrate for ribozyme cleavage. the design of the ribozyme was based on that of the hammerhead structure of the satellite tobacco ringspot autolytic processing sequence. specificity to the n-ras substrate was conferred by 10 nucleotides homologous to the target site on the mrna positioned on either side of the catalytic unit ...19911668256
generation of c127-derived cell lines expressing estrogen or progesterone receptors for studying gene regulation on bovine papilloma virus minichromosomes.to study regulation of transcription by multiple steroid hormones we have stably introduced expression vectors for human estrogen and rabbit progesterone receptors into the genome of the murine fibroblast cell line c127. these cells express functional endogenous glucocorticoid receptor and support bovine papilloma virus minichromosomes, a useful system for studying the role of chromatin structure on gene expression. three clones containing progesterone receptor integrates and six containing estr ...19911668831
expression and function of normal and lncap androgen receptors in androgen-insensitive human prostatic cancer cells. altered hormone and antihormone specificity in gene transactivation.the gene for the androgen receptor (ar) in the androgen-sensitive human prostate cancer cell line lncap has a single-base mutation that produces a threonine to alanine change in the androgen-binding domain. androgen-insensitive prostatic cancer (pc-3) cells were cotransfected with an expression vector encoding normal, lncap, or chimeric normal/lncap ar and a vector carrying a chloramphenicol acetyltransferase (cat) reporter gene linked to the mouse mammary tumor virus promoter. cat activity was ...19911668832
identification and characterization of a cis-acting element that interferes with glucocorticoid-inducible activation of the mouse mammary tumor virus promoter.the rat hepatoma cell line m1.19 is stably infected by the mouse mammary tumor virus (mmtv), and the expression of the virus is induced by glucocorticoid treatment. however, in the 6.10.2 variant of m1.19, an increase in mmtv transcription is hardly detectable upon exposure to hormone. the mechanism of hormone-unresponsiveness in these cells has been unclear. in this study, we show that nuclear extract from 6.10.2 cells contains a specific dna-binding activity that recognizes a sequence motif ex ...19911647031
differential regulation of mouse mammary tumor virus-bacterial chloramphenicol acetyltransferase chimeric gene by human mineralocorticoid hormone-receptor complexes.the brain tissues of the rat and mouse express two types of corticosteroid binding proteins, the glucocorticoid (gr) and aldosterone (mr) receptors. unlike the type ii (gr) receptor, type i receptor has a high affinity for aldosterone (aldo) and corticosterone and is structurally similar to the kidney mineralocorticoid receptor (mr). the results reported in this study provide direct evidence for the interaction of dexamethasone (dex), triamcinolone acetonide (ta), dexamethasone-21-mesylate (dxm) ...19911648951
characterisation of functional inhibition of the glucocorticoid receptor by fos/jun.we have studied the effects of fos and fos/jun on glucocorticoid induction of hormone-sensitive gene expression. in nih3t3 cells overexpression of fos or fos/jun by transfection of psv2-fos and psv2-jun inhibited glucocorticoid-dependent expression of mmtv ltr-cat. expression of p39v-mos had a similar effect on glucocorticoid-dependent reporter gene expression which is most likely mediated by simulation of endogenous fos. in both cases, this inhibition could be overcome by overexpression of the ...19911650443
mechanisms controlling steroid receptor binding to specific dna sequences.mammalian progesterone receptors activated by hormone binding in nuclei of intact cells exhibit substantially higher binding activity for specific dna sequences than receptors bound with hormone and activated in cell-free cytosol. differences in dna-binding activity occur despite the fact that both activated receptor forms sediment at 4s on sucrose gradients and are apparently dissociated from the heat shock protein 90. this suggests that hormone-induced release of heat shock protein 90 from rec ...19911652169
the mouse biliary glycoprotein gene (bgp): partial nucleotide sequence, expression, and chromosomal assignment.transcripts related to the human carcinoembryonic antigen were found in mrna isolated from both dimethylbenzanthracene-induced and mouse mammary tumor virus-induced mammary tumors. a cdna library was prepared from a dimethylbenzanthracene-induced tumor, and a clone was isolated by hybridization with a human carcinoembryonic antigen cdna probe. its sequence, when compared to those of members of the human carcinoembryonic antigen gene family, was most homologous to the sequence of the human biliar ...19911653760
dietary restriction permits normal parturition and lactation but suppresses mouse mammary tumor virus proviral transcription even after mammary involution.dietary restriction of c3h/ou mice prevents development of spontaneous mammary adenocarcinoma by suppressing mammary expression of the mouse mammary tumor virus (mmtv) via a mechanism which may involve prolactin. in the present study, dietary restriction of 40% was imposed for 16 weeks on nulliparous c3h/ou mice, interrupted by ad libitum consumption at mating and continued only during pregnancy and lactation, with 40% energy restriction reimposed at the end of lactation. the results show that m ...19911655246
co-segregation of a gene encoding a deletion ligand for tcrb-v3+ t cells with mtv-3.a gene encoding the endogenous superantigen mlsc, which deletes tcrb-v3+ t cells in the nod inbred mouse strain, was found to co-segregate with mtv-3 on chromosome 11. this identifies a fourth gene encoding a deletion ligand for tcrb-v3+ t cells and extends recently published observations in support of the hypothesis that a number of endogenous superantigens are the products of mtv proviruses.19911655644
expression of mouse mammary tumor virus glycoprotein truncations defines roles for the transmembrane domain and ectodomain hydrophobic region in constitutive exocytic trafficking and proteolytic processing.a mutational analysis was used to identify structural domains that are important for exocytic transport and proteolytic cleavage of the mouse mammary tumor virus (mmtv) glycoprotein, which is expressed as a multidomain polyprotein. rat htc hepatoma cells were transfected with the mmtv glycoprotein gene driven by the constitutive rous sarcoma virus promoter, with mutant genes encoding a series of polypeptide truncations or with a defective mmtv provirus containing a premature termination codon in ...19911655786
physiologic expression of two superantigens in the bdf1 mouse.the majority of endogenous superantigens in the mouse (including the mls loci) is encoded by mouse mammary tumor proviruses (mtv) carried in the germline. to understand the differences between the highly stimulatory viral superantigens such as mls-1a (encoded by mtv-7), which have biologic activity in vivo and in vitro, and the poorly stimulatory viral superantigens such as etc-1 (encoded by mtv-9), which are active only in vivo, the physiologic expression of each ag was studied in the mtv-7+ (m ...19911655891
detection and characterization of a glycoprotein encoded by the mouse mammary tumor virus long terminal repeat gene.mouse mammary tumor virus (mmtv) is a retrovirus that causes mammary tumors in susceptible mice. mmtv contains a unique open reading frame (orf) in the unique 3' region of the proviral long terminal repeat (ltr) with the potential to encode a 36-kda protein. however, the orf gene product has not been detected in murine mammary tissues or cell lines. we utilized the baculovirus expression vector system to generate large amounts of the orf protein. putative orf gene products of 36 and 45 kda were ...19911656086
inhibition of chromatin assembly in xenopus oocytes correlates with derepression of the mouse mammary tumor virus promoter.the mouse mammary tumor virus (mmtv) promoter is positively regulated by glucocorticoid hormone via binding of glucocorticoid receptor to a specific response element. upon addition of hormone, a nucleosome containing the glucocorticoid response element is removed or structurally altered, suggesting that the nucleosome interferes with transcription. accordingly, inhibition of chromatin assembly should relieve the repression and result in an increased constitutive activity. we have tested this hyp ...19911656227
expression of the c-ha-ras oncogene in mouse nih 3t3 cells induces resistance to cisplatin.the effect of expression of the c-ha-ras oncogene on cisplatin (ddp) sensitivity was examined in murine nih 3t3 cells transfected with the dexamethasone (dex)-inducible mouse mammary tumor virus promoter linked to an activated c-ha-ras gene [ltr h-ras(a) cells]. treatment of these cells with 5 microm dex for 24 h induced c-ha-ras expression and produced an 8.2 +/- 1.3-fold (sd) increase in ddp resistance as quantitated by clonogenic assay. induction of the c-ha-ras oncogene reduced ddp accumulat ...19911657373
an optimum dose of c-h-ras is a prerequisite for hormone-dependent conversion of a cell between cancerous and normal states in tissue culture.we have established a few cell lines which can be reversibly converted from cancerous to normal and vice versa by the addition to, or removal from the culture medium of glucocorticoid hormone. these cell lines were derived from mouse nih 3t3 cells and possessed the integrated gene pairs on chromosomes, which are composed of human mutated c-h-ras fused with mouse mammary tumour virus long terminal repeat and e. coli xanthine-guanine phosphoribosyltransferase gene with the sv40 promoter. we have c ...19911657409
regulation of glucocorticoid receptor expression in cultured fibroblasts from a patient with familial glucocorticoid resistance.the thermolabile glucocorticoid receptor (gr) in fibroblasts from a patient with familial glucocorticoid resistance (fgr) was characterized by solution hybridization, northern blot analysis and western immunoblotting using an hgr and crna probe and a gr specific monoclonal antibody. specific dna binding was measured by binding of cytosolic gr to mouse mammary tumour virus (mmtv) dna. northern blot analysis of total cellular rna isolated from the fibroblasts showed hybridization of the hgr probe ...19911659867
characterization of int-5, a locus associated with early events in mammary carcinogenesis.three chemically-induced precancerous mammary hyperplasias, independently isolated in balb/c mice, all contained mouse mammary tumor virus (mmtv) proviral dna integrated into a common region in chromosomal dna, designated int-5 (formerly int-h, gray et al., 1986). this site was cloned from a hyperplastic outgrowth (d2) into lambda phage. a 1.7 kb hind iii dna fragment, which flanks the 5' end of the mmtv insert, was generated from the cloned int-5 region. this fragment was used as probe (ih-2) t ...19911705320
the different activation of int genes in mammary carcinomas developed in three mouse strains harboring mouse mammary tumor viruses derived from dd/tbr.rna expressions of common integration site (int) genes and several oncogenes were investigated in mammary carcinomas spontaneously developed in different three strains of mice; dd/tbr, nih swiss and balb/c which harbor dd-mmtv derived from dd/tbr mouse. latter two strains of mice were designated nih/mtv+ and balb/mtv+, respectively. an increased expression of int-1 (wnt-1) and int-2 genes was observed in 56% (9/16) and 50% (8/16) of mammary carcinomas of dd/tbr mice, respectively. either int-1 o ...19911660818
multipartite structure of a negative regulatory element associated with a steroid hormone-inducible promoter.the steroid hormone-inducible promoter from mouse mammary tumor virus is associated with a distal negative regulatory element that represses its inherent basal activity. deletion analysis localized the sequences required for repression to 64 base pairs of dna between -427 and -364 with respect to the transcription initiation site. transient transfection experiments with a series of linker scanning and small internal deletion mutations revealed two mutation-sensitive domains separated by a region ...19911660891
growth inhibition of murine mammary carcinoma by monoclonal ige antibodies specific for the mammary tumor virus.two ige-producing hybridomas were established from spleen cells of balb/c mice, which had been immunized with mouse mammary tumor virus (mmtv). these ige monoclonal antibodies (mabs) reacted specifically with the major envelope glycoprotein (gp36) of mmtv, as established by the immunoblot assay and by passive cutaneous anaphylaxis. the effect of the ige mabs (produced by clone a8) on the growth of the mmtv-secreting mammary adenocarcinoma h2712 was investigated in syngeneic c3h/hej mice. the mic ...19911662114
expression of activated oncogenes in the murine mammary gland: transgenic models for human breast cancer.breast cancer is the leading cause of death among non-smoking women and thus has been the focus of intensive research. it has been generally accepted that the deregulation of oncogenes or their regulators play a pivotal role in progression of this prevalent disease. for example, amplification and overexpression of a number of oncogenes has been observed in a proportion of primary breast cancer biopsies. more recently, there has also been reports of inactivation tumor suppressor genes in human br ...19911662559
tissue distribution of the cellular binding protein for the mouse mammary tumour virus.the envelope protein, gp52, of the mouse mammary tumour virus (mmtv) binds to a cell-surface receptor as a first step in infection. a protein with characteristics of this receptor was measured on freshly isolated cells using, as ligand, 125i-labelled gp52 purified from c3h/hen mice. the gp52-binding protein was found in all mouse tissues examined, but was present at highest concentrations in the mammary gland and spleen where it reached 4.2 +/- 0.3 (s.e.m.) pmol/mg protein; the dissociation cons ...19911663754
altered effects of glucocorticoids on the trafficking and processing of mouse mammary tumor virus glycoproteins constitutively expressed in rat hepatoma cells in the absence of nonglycosylated viral components.we have documented previously that glucocorticoid hormones modulate the posttranslational localization of cell surface mouse mammary tumor virus (mmtv) glycoproteins in the viral-infected m1.54 rat htc hepatoma cell line. to determine whether glucocorticoids affect the trafficking of individually synthesized mmtv glycoproteins, htc cells were transfected with a constitutively expressed mmtv glycoprotein gene lacking the viral phosphoprotein and polymerase genes. this construct also allows equiva ...19911664047
host genetic background effect on the frequency of mouse mammary tumor virus-induced rearrangements of the int-1 and int-2 loci in mouse mammary tumors.the frequency with which int-1 and int-2 are rearranged in mouse mammary tumors by mouse mammary tumor virus (mmtv)-induced insertional mutagenesis is a consequence of the host genetic background. in 75% of c3h mammary tumors, int-1 is rearranged by mmtv insertion, whereas only 30% of balb/cfc3h tumors contain a virus-induced rearrangement of int-1. this difference is significant (p less than 0.005) and could not be accounted for by the potentially additive effect of the genetically transmitted ...19911712864
sequence homology of deoxyribonucleic acid to mouse mammary tumor virus genome in human breast tumors.fifty-two human breast tumors were screened for the presence of dna homology to mouse mammary tumor virus (mmtv) using molecularly cloned mmtv proviral genomic dna probes and dot-blot hybridization. seven patients were found to contain an entire provirus (gag, pol, env, and ltr positive at high stringency). fifty percent (5/10) of patients having a first degree relative with breast carcinoma were found to have dna homology to the gag-pol portion of the mmtv genome when hybridization and washing ...19911664195
in two genes, synergism of steroid hormone action is not mediated by cooperative binding of receptors to adjacent sites.synergistic action of multiple steroid hormone response elements (hres) has been proposed to be due to cooperative binding of receptors. we have studied the cooperativity of steroid hormone receptor binding to synergistic hres in two natural genes. in the mouse mammary tumor virus long terminal repeat that contains four progesterone receptor binding sites, no cooperativity in receptor binding was observed between the single distal and the three proximal sites whereas a low level of cooperativity ...19911665457
binding of glucocorticoid receptors to model dna response elements.dna sequences were synthesized that contained the consensus 15-base pair glucocorticoid receptor binding site linked to flanking sequences of various lengths. binding of these synthetic oligomers to glucocorticoid receptor, employing a reconstituted binding system with purified components, indicated that a minimal size of approximately 45 base pairs was necessary to bind the receptor optimally. sequences containing multiple receptor binding sites competed more effectively for binding. these find ...19911665494
growth complementation of influenza virus temperature-sensitive mutants in mouse cells which express the rna polymerase and nucleoprotein genes.in order to establish cell lines which complement the growth of temperature-sensitive (ts) mutants of influenza virus, three rna polymerase and nucleoprotein (np) genes each linked to the mouse mammary tumor virus ltr were cloned into the bovine papillomavirus vector dna. after co-transfection of mouse c127 cells with these recombinant plasmids, a cell line, clone 76, in which the expression of the three polymerase and np genes could be stimulated by dexamethasone, was established. the clone 76 ...19911663110
molecular insights into breast cancer from transgenic mouse models.we desperately need to know more of the biological details of the onset and progression of breast cancer. the disease is of startlingly high incidence (approaching 1 in 9 women), our current therapies for the disease are inadequate once it has metastasized, and the disease is characterized by excessive morbidity and mortality. most of the growth and differentiation of the mammary gland occurs relatively late in life: during sexual maturation, and then cyclically during pregnancy and lactation. n ...19911663341
rna pseudoknots downstream of the frameshift sites of retroviruses.rna pseudoknot structural motifs could have implications for a wide range of biological processes of rnas. in this study, the potential rna pseudoknots just downstream from the known and suspected retroviral frame-shift sites were predicted in the rous sarcoma virus, primate immunodeficiency viruses (hiv-1, hiv-2, and siv), equine infectious anemia virus, visna virus, bovine leukemia virus, human t-cell leukemia virus (types i and ii), mouse mammary tumor virus, mason-pfizer monkey virus, and si ...19911663382
mls, mtv, and t cells: possible roles in retroviral diseases. 19911657087
iron enhances tumor growth. observation on spontaneous mammary tumors in mice.iron is essential for the growth of all cells, including tumor cells. the authors previously reported that a variety of transplantable tumors grew faster and larger in mice that were on an iron-rich diet compared with those on an iron-deficient diet. in this study the authors examined the relationship between iron in the diet and development of tumors in mice that are known to develop spontaneous tumors--c3h/hen-mtv+(c3h-mtv+) mice that were congenitally infected with mammary tumor virus. these ...19911657354
transcriptional regulation of mouse mammary tumor virus by steroid hormones. 19911653620
the production of human monoclonal anti-mmtv antibodies by in vitro immunization with anti-idiotypic antibodies.we have previously reported the production of a series of human monoclonal antibodies reacting with mouse mammary tumor viral antigens as well as the human counterpart humtv antigen. against two of these antibodies (b11 and 4.6/6), anti-idiotypic antibodies were generated, which appeared to be the internal image of viral antigen. vaccination with the anti-idiotypic antibodies induced in mice humoral and cellular immunity against both mmtv and humtv. the current study describes a novel method to ...19911649130
polyoma virus middle tumor antigen stimulates membrane-associated protein kinase c at lower levels than required for phosphatidylinositol kinase activation and neoplastic transformation.twelve independent rat f111 cell lines expressing the polyoma virus middle tumor antigen (mt) under control of the dexamethasone-regulatable mmtv-ltr promoter were assayed for levels of membrane-associated protein kinase c (pkc) activity. low background levels of mt antigen expression (approximately 2%), although insufficient for transformation, triggered a dramatic increase in pkc activity. under the same conditions, levels of the mt-associated phosphatidylinositol kinase activity were low, ind ...19911648699
oncogenicity of the ret transforming gene in mmtv/ret transgenic mice.we have successfully produced transgenic mice that carry the ret oncogene driven by a mouse mammary tumor virus promoter/enhancer. mammary and salivary gland adenocarcinomas were developed in a stochastic fashion in these mice. moreover, premalignant tumors with hyperplastic and dysplastic lesions of harderian glands and male reproductive tracts frequently occurred at young ages. high expression of the transgene was closely associated with the development of these tumors although the levels of t ...19901691479
structural determinants of a glucocorticoid receptor recognition element.analysis of the relative inducibility of an extensive series of mutant glucocorticoid response elements (gres) defines features critical to the constitution of an active gre. assuming that function as a gre reflects binding of glucocorticoid receptor, our activity data are consistent with the recognition of the gre as two hexamer half-sites, each half-site recognized by a single subunit of a receptor dimer, probably in a cooperative fashion. integrity of both half-sites is necessary for an activ ...19901964489
association of hst gene expression with metastatic phenotype in mouse mammary tumors.from the pregnancy-dependent mouse mammary tumor tpdmt-4, four autonomous sublines were established after its independent progression under different conditions. despite their similar growth rates in inguinal fat pads, three sublines formed lung metastases, and one did not when they were injected i.v. into mice as a single cell suspension. the tpdmt-4 tumor and the nonmetastatic subline expressed mrna for the orf gene of mouse mammary tumor virus, whereas all metastatic sublines did not. this su ...19901964796
translational frameshift suppression in mouse mammary tumor virus and other retroviruses.retroviruses, related retroposons, and several rna viruses use translational frameshifting in the expression of their polymerase genes. we use retroviruses, particularly mouse mammary tumor virus, to illustrate the model which reflects our current understanding of these site-specific frameshifting events. the model has two components, a shifty sequence that facilitates ribosome slippage, and a second signal, either rna secondary structure or an unfilled ribosomal a site, that stalls the ribosome ...19901966844
nucleosome positioning modulates accessibility of regulatory proteins to the mouse mammary tumor virus promoter.minichromosomes containing the mmtv hormone responsive element (hre) exhibit precisely positioned nucleosomes. chromatin reconstitution of short hre dna fragments also results in precise positioning of nucleosomes as revealed by footprinting, which suggests that information for nucleosome phasing is contained within this short sequence. while hormone receptors bind naked dna and reconstituted nucleosomes with similar affinities (3- to 5-fold difference), nfi, a transcription factor essential for ...19902155706
a glucocorticoid-resistant rat hepatoma cell variant contains functional glucocorticoid receptor.the mechanism of glucocorticoid resistance was studied in a rat hepatoma cell variant (6.10.2) which contains low levels of glucocorticoid receptor. these cells seem to have lost glucocorticoid-induced transcriptional responses as measured by the induction of expression of stably integrated mouse mammary tumor virus gene and the endogenous tyrosine aminotransferase gene, as well as the transcriptional suppression of glucocorticoid receptor gene expression. however, characterization of the glucoc ...19901970570
prolactin effects on the dietary regulation of mouse mammary tumor virus proviral dna expression.chronic energy-intake restriction inhibits mouse mammary tumor virus (mmtv)-induced mammary tumors in c3h/ou mice by greater than 90%. we have shown that associated with suppression of mammary tumorigenesis there is a reduction or inhibition of circulating prolactin, mmtv particles expressed, and mmtv mrna transcription in mammary glands (and in most organs tested). to understand the concerted action of prolactin, energy-consumption level, and mmtv on inducing mammary tumors, experiments were de ...19901975696
harderian gland pathology in transgenic mice carrying the mmtv/v-ha-ras gene.twenty-four harderian glands from 16 transgenic mice carrying a v-ha-ras gene under the control of the mouse mammary tumor virus promoter were examined histologically upon death of the animals. eight glands were histologically normal and eleven were hyperplastic. four additional glands showed predominantly hyperplasia, but also contained foci of dysplasia and in situ carcinoma. one gland contained an adenocarcinoma. the range of pathology observed in the harderian glands of these transgenic mice ...19902156784
insertion mutation of the int-1 and int-2 loci by mouse mammary tumor virus in premalignant and malignant neoplasms from the gr mouse strain.mouse mammary tumor virus (mmtv)-induced mammary adenocarcinomas can develop from several different premalignant precursors common in gr mice. insertion mutagenesis of the mammary protooncogenes int-1 and int-2 was studied in this multistep system by analyzing samples from various stages of neoplastic development for novel int-1 and int-2 restriction fragments generated by mmtv provirus integration. int-1 and int-2 insertion mutations were observed in both premalignant lesions and malignant tumo ...19902157060
transforming growth factor-beta represses transcription of the mouse mammary tumour virus dna in cultured mouse mammary cells.increased expression of mouse mammary tumour virus (mmtv) is associated with hyperplastic alveolar growth and subsequent development of mammary cancers in the mouse. the expression of this virus is repressed when mammary tumour cells undergo sarcomatous transformation. we have demonstrated that a spontaneous progression of mouse mammary adenocarcinoma cells into highly malignant cells with the transformed phenotype is accompanied by an increased expression of transforming growth factors alpha an ...19902157176
acquired expression of hst-1 in an autonomous subline (chiba subline 2) derived from androgen-responsive mouse mammary tumor (shionogi carcinoma 115).since growth of shionogi carcinoma 115 (sc 115) and its autonomous subline (cs 2) were regulated by fibroblast growth factor-like peptide, expression of int-2 and hst-1 was examined in these cell lines. hybridization of genomic dna with long terminal repeat of mouse mammary tumor virus (mmtv) revealed the same pattern of restriction fragments, showing the same integration of mmtv. although weak expression of int-2 was noticed in the two cells, clear expression of hst-1 was seen only in cs 2 cult ...19901976117
molecular events in b lymphocyte differentiation. inducible expression of the endogenous mouse mammary tumor proviral gene, mtv-9.we have previously shown that the steady state levels of transcripts encoded by an endogenous mouse mammary tumor virus (mmtv) increase during lps-induced differentiation of both normal b lymphocytes and an inducible b cell lymphoma, ch12. a large body of evidence suggests that mmtv expression is primarily limited to mammary tissues and that expression in cell lines from nonmammary tissues is accompanied by viral amplification and alterations in the transcriptional control regions of the viral l ...19902157765
a congenic line of the ddd mouse strain, ddd/1-mtv-2/mtv-2: establishment and mammary tumorigenesis.a single dominant gene on chromosome 18, mtv-2, controls both the early appearance of mammary tumors and expression of mouse mammary tumor virus (mmtv) in the milk. a congenic ddd mouse strain, ddd/1-mtv-2/mtv-2 (ddd-mtv-2), was developed by introducing this gene from grs/ajms (gr) into ddd/1 mice by repeating 12 backcrosses and subsequent inbreeding using mammary tumors as a marker for selection. southern blot analysis of the liver dna from the resulting congenic mice with ecori and mmtv-u3 pro ...19901976120
glucocorticoids locally disrupt an array of positioned nucleosomes on the rat tyrosine aminotransferase promoter in hepatoma cells.transcriptional activation by steroid hormones is often associated with the appearance of a dnase i hypersensitive site resulting from a local alteration of the nucleoprotein structure of the promoter. for the mouse mammary tumor virus long terminal repeat, a viral promoter under glucocorticoid control, a model has been proposed: the appearance of the hormonodependent dnase i hypersensitive site reflects the displacement of a single precisely positioned nucleosome associated with the glucocortic ...19901979170
oncogene n-ras mediates selective inhibition of c-fos induction by nerve growth factor and basic fibroblast growth factor in a pc12 cell line.a cell line was generated from u7 cells (a subline of pc12 rat pheochromocytoma cells) that contains a stably integrated transforming mouse n-ras (lys-61) gene under the control of the long terminal repeat from mouse mammary tumor virus. such cells, designated ur61, undergo neuronal differentiation upon exposure to nanomolar concentrations of dexamethasone, as a consequence of expression of the activated n-ras gene (i. guerrero, a. pellicer, and d.e. burstein, biochem, biophys. res. commun. 150: ...19902108319
the int-2 gene product acts as an epithelial growth factor in transgenic mice.the induction of mammary tumors by mouse mammary tumor virus (mmtv) is thought to occur through proviral activation of one or more cellular genes. one of these, int-2, encodes a 27 kd protein which exhibits striking homology to the basic fibroblast growth factor family. to assess directly the role of the int-2 protein in cell proliferation, we have established transgenic mice which carry the int-2 gene driven by the mmtv promoter/enhancer. expression of the int-2 gene in female transgenic mice r ...19901690126
lack of evidence for the involvement of type-c and type-b retroviruses in radiation leukemogenesis of nfs mice.southern blot analysis revealed no difference between the dna from radiation-induced thymic lymphomas and dna from normal nfs mice. the probes used in the southern blot analyses used a murine leukemia virus (mulv) env dna probe (pxenv), which specifically hybridizes with xenotropic and recombinant viral env genes, and mouse mammary tumor virus (mmtv) dna probes (mmtv gag-pol, mmtv env, and mmtv ltr). this suggests that radiation leukemogenesis was not associated with gross alteration of the orga ...19901690435
the wnt-1 (int-1) oncogene promoter and its mechanism of activation by insertion of proviral dna of the mouse mammary tumor virus.wnt-1 (int-1) is a cellular oncogene often activated by insertion of proviral dna of the mouse mammary tumor virus. we have mapped the 5' end and the promoter area of the wnt-1 gene by nuclease protection and primer extension assays. in differentiating p19 embryonal carcinoma cells, in which wnt-1 is naturally expressed, two start sites of transcription were found, one preceded by two tata boxes and one preceded by several gc boxes. in p19 cells, a 1-kilobase upstream sequence of wnt-1 was able ...19901695322
regulated expression of vimentin cdna in cells in the presence and absence of a preexisting vimentin filament network.human cells were transfected with a mouse vimentin cdna expression vector containing the hormone response element of mouse mammary tumor virus. the distribution of mouse vimentin after induction with dexamethasone was examined by indirect immunofluorescence with antivimentin antibodies specific for either mouse or human vimentin. in stably transfected hela cells, which contain vimentin filaments, addition of dexamethasone resulted in the initial appearance of mouse vimentin in discrete areas, us ...19901696263
altered mouse mammary tumor virus transcript synthesis in t-cell lymphoma cells.proviral copies of mouse mammary tumor virus (mmtv) are known to be amplified in certain t-cell lymphomas. transcription of the amplified mmtv proviruses was studied in detail in two t-cell lymphoma lines and showed the production of deletions and premature termination of env mrnas and the premature termination of gag transcripts. el-4 cells produce three env mrnas, and sequence analysis of cdnas of the two smaller transcripts revealed large deletions encompassing the 3' half of the env gene. th ...19901696633
immortalization and transformation of human fibroblasts by regulated expression of polyoma virus t antigens.we have established conditions for the immortalization of human fibroblasts by the large t antigen of the rodent virus polyoma. this allows the mechanism of immortalization to be studied, without interference by transformation events, in cells with relatively stable chromosomes. large t antigen could immortalize human fibroblasts if expression was driven by a heterologous promoter like the immediate early promoter/enhancer of cytomegalovirus or the inducible mouse mammary tumour virus (mmtv) pro ...19901697410
gene expression in cells infected with gammaherpesvirus saimiri: properties of transcripts from two immediate-early genes.during productive infections of cells with the gammaherpesvirus, herpesvirus saimiri (hvs), a polyadenylated rna of 2.2-2.4 kb accumulates to form a large fraction of virus-specified rna. this transcript is from the virus thymidylate synthase (ts) gene and its synthesis, like that of late mrnas encoding the virus structural proteins, is sensitive to an inhibitor of virus dna synthesis (phosphonoacetic acid, paa). transcription which is insensitive to paa occurs from many parts of the hvs genome, ...19901699352
negative regulation in correct tissue-specific expression of mouse mammary tumor virus in transgenic mice.mouse mammary tumor virus (mmtv) is an endogenous murine retrovirus that is expressed in the epithelial cells of the mammary and salivary glands, lungs, kidneys, and seminal vesicles and in the lymphoid cells of the spleen and thymus. several studies have shown that the long terminal repeat (ltr) of this virus can direct the expression of reporter genes to the same tissues in transgenic mice. to determine whether multiple regulatory elements within the ltr are involved in this tissue-specific ex ...19901700274
a glucocorticoid response element enhances transcription of a methionine trna gene in cis and trans.in vitro transcription experiments using a xenopus laevis cell-free extract have demonstrated that a dna fragment containing a glucocorticoid response element (gre) significantly enhances the expression of a methionine trna gene. this stimulation can be observed when the element is located in cis or trans. in the cis configuration, the element can be located 2900 basepairs from the gene and still display transcriptional enhancement. in trans, the enhancement can occur at a low element to templat ...19901963472
molecular biology of type a endogenous retrovirus.intracisternal a particles (iaps) are retrovirus-like structures consistently observable in a variety of mouse tumor cells such as myeloma and hybridoma and in early embryonic cells derived from rodents but nothing is known of their infectivity. mouse iaps contain a gag-like protein, a reverse transcriptase and a polyadenylated rna molecule (iap rna). dna sequences complementary to iap rna (iap genome) are interspersedly present in rodent such as mice, rats, chinese hamsters and syrian hamsters ...19901710682
effect of a dominant inhibitory ha-ras mutation on mitogenic signal transduction in nih 3t3 cells.we used a dominant inhibitory mutation of c-ha-ras which changes ser-17 to asn-17 in the gene product p21 [p21(asn-17)ha-ras] to investigate ras function in mitogenic signal transduction. an nih 3t3 cell line [nih(m17)] was isolated that displayed inducible expression of the mutant ha-ras gene (ha-ras asn-17) via the mouse mammary tumor virus long terminal repeat and was growth inhibited by dexamethasone. the effect of dexamethasone induction on response of quiescent nih(m17) cells to mitogens w ...19902118993
negative growth regulation in a glioblastoma tumor cell line that conditionally expresses human wild-type p53.to investigate the effect that human wild-type p53 (wt-p53) expression has on cell proliferation we constructed a recombinant plasmid, pm47, in which wt-p53 cdna is under transcriptional control of the hormone-inducible mouse mammary tumor virus promoter linked to the dominant biochemical selection marker gene eco gpt. the pm47 plasmid was introduced into t98g cells derived from a human glioblastoma multiforme tumor, and a stable clonal cell line, gm47.23, was derived that conditionally expresse ...19902143581
induction of a variety of tumors by c-erbb2 and clonal nature of lymphomas even with the mutated gene (val659----glu659).the c-erbb2 gene is expressed uniquely in fetal epithelium in vivo and has been suggested to contribute to the development and/or progression of adenocarcinomas in man. in order to assess the oncogenicity of the c-erbb2 gene in vivo, normal c-erbb2 and mutant c-erbb2 encoding glutamic acid instead of valine at position 659 within the transmembrane domain were introduced into mice under the transcriptional regulatory unit of mouse mammary tumor virus long terminal repeat (mmtv-ltr) or immunoglobu ...19902153076
cloning of minute virus of mice cdnas and preliminary analysis of individual viral proteins expressed in murine cells.cdnas corresponding to rna from the autonomous parvovirus minute virus of mice were cloned into constitutive and inducible expression vectors. these clones generate viral ns2, vp1, and vp2 proteins individually. initial examination of these clones by transient expression analysis and analysis of stably transformed murine cell lines inducibly expressing these constructs indicated that they will be useful tools for characterizing the function of individual minute virus of mice gene products.19902164605
activation of retrovirus in transgenic mice: association with development of olfactory neuroblastoma.a line of transgenic mice that express the human adenovirus type 12 e1a and e1b genes under the regulatory control of the mouse mammary tumor virus long terminal repeat was studied. mice from this line develop olfactory neuroblastomas at approximately 6 months of age. large numbers of type c retrovirus (ecotropic murine leukemia virus) particles were found in the tumor rosettes. no similar examples of virus activation were identified in tumors from other transgenic experiments. examination of sp ...19902164606
proviral insertions within the int-2 gene can generate multiple anomalous transcripts but leave the protein-coding domain intact.we examined the effects of mouse mammary tumor virus integration on the multiple rna transcripts expressed from the int-2 proto-oncogene in virally induced breast tumors. proviral insertion either upstream or downstream of the gene could simultaneously activate transcription from three dissimilar int-2 promoters. in some tumors, the activating provirus lies within the transcription unit and disrupts the structures of the various rnas. insertions in the 5' region of the gene had complex effects d ...19902153243
the int genes in mouse mammary tumorigenesis and in normal development.in mice, the mouse mammary tumour virus causes tumours by insertional activation of host cell oncogenes. by the application of transposon tagging techniques, several cellular oncogenes, called int, have been discovered. the int-1 gene encodes a cysteine-rich protein with a signal peptide, suggesting that it may act as an extracellular growth or differentiation factor. normally, the int-1 gene is expressed in early embryogenesis of the mouse, in particular in the developing nervous system. the es ...19902164908
in vitro and in vivo growth and casein gene expression of mouse mammary tumor epithelial cells in response to hormones.cells from autochthonous mouse mammary carcinomas which display estrogen-independent growth in vivo were studied for their hormonal responses in primary culture. a culture system employing insulin-supplemented, serum-free medium and basement membrane matrigel as a substratum was used to cultivate tumor cells. the cells did not exhibit in vitro estrogen- or prolactin-dependent growth. primary tumors still displayed a constitutional expression of alpha-, beta-, and gamma-casein mrnas. these messag ...19902153557
hormonal induction of transfected genes depends on dna topology.plasmids containing the hormone regulatory element of mouse mammary tumor virus linked to the thymidine kinase promoter of herpes simplex virus and the reporter gene chloramphenicol acetyltransferase of escherichia coli respond to glucocorticoids and progestins when transfected into appropriate cells. in the human mammary tumor cell line t47d, the response to progestins, but not to glucocorticoids, is highly dependent on the topology of the transfected dna. although negatively supercoiled plasmi ...19902153920
growth factors induce phosphorylation of the na+/h+ antiporter, glycoprotein of 110 kd.the na+/h+ antiporter, which regulates intracellular ph in virtually all cells, is one of the best examples of a mitogen- and oncogene-activated membrane target whose activity rapidly changes on stimulation. the activating mechanism is unknown. a na+/h+ antiporter complementary dna fragment was expressed in escherichia coli as a beta-galactosidase fusion protein, and a specific antibody to the fusion protein was prepared. use of this antibody revealed that the na+/h+ antiporter is a 110-kilodalt ...19902154036
demonstration of a new mouse mammary tumor virus locus in the genome of the mammary tumor prone strain shn mouse.until this report, there have been no detailed analyses of the mouse mammary tumor virus (mmtv) loci in the mammary tumor prone strain shn. using a probe, which hybridizes to the env sequence of mmtv, southern blotting of genomic dna from the brain after digestion with ecori revealed 5 endogenous proviruses: mtv-1 (4.5kb), mtv-2 (11 kb), mtv-8 (6.7kb), mtv-17 (8.3kb) and a newly-found 6.5-kb fragment. f1-hybrid mice (c3h/he female x shn male) also possessed the 6.5-kb fragment. thus, we conclude ...19902154203
mouse mammary tumor virus (mmtv) infection in swiss and riii mice. correlation between resistance to exogenous infection and anti-mmtv serum response.host-virus relationships were examined in mice from the two mouse mammary tumor virus (mmtv)-infected strains swiss mb+ and riii, which harbour the same mmtv variant, and from the derived sublines swiss mb- and riiif, which were freed of milk-borne mmtv by foster-nursing. these two strains are not phylogenetically related, the swiss strain bearing the endogenous mtv-3 locus in its dna. in riii and swiss mb+ mice, the incidence of early mammary tumors, which was of 96% and 8%, respectively, was c ...19902167058
[molecular mechanisms of mmtv-induced tumor development]. 19902155437
progesterone receptor stimulates transcription of mouse mammary tumour virus in a cell-free system.in higher eukaryotes, steroid receptors are general modulators of gene activity which bind to dna hormone response elements (hres) in the vicinity of regulated promoters. analysis of mutant and chimaeric receptor proteins in gene transfer experiments has identified the domains responsible for hormone binding, interaction with the hres and transactivation, but the transactivating function of hormone receptors has proved difficult to reproduce in cell-free assays. here we describe a crude in vitro ...19902156171
distribution of mouse mammary tumor virus-related sequences does not correlate with the taxonomic position of their hosts.sequences (mrs) distantly related to mouse mammary tumor virus (mmtv) were found in genomes of a wide range of mammalian species using blot hybridization. the number of mrs copies and the degree of their homology with the hybridization probe varied and did not correlate with the taxonomic position of the species. nevertheless, within a genus the set of mrs was species specific and reflected the taxonomic relation between the species. mrs were also found in avian genomes and the degree of their h ...19902168108
influence of mammary cell differentiation on the expression of proteins encoded by endogenous balb/c mouse mammary tumor virus genes.the interactions between differentiation-associated cellular events in the intact mammary gland or in cultured mammary cells and the post-transcriptional activity of the endogenous mouse mammary tumor virus (mmtv) loci were investigated. the transcriptional activities of the endogenous mmtv proviruses of the balb/c mouse strain (mtv-6, mtv-8 and mtv-9) appear to be regulated differentially during pregnancy-induced mammary gland development (j.e. knepper, d. medina and j.s. butel, j. virol. 59, 5 ...19902168113
dna rearrangements of the int region in spontaneous mouse mammary tumors of shn/s and sln/s mice.shn and sln mice originating from the same swiss albino stock are genetically very close to each other. the incidence and latent period of mammary tumor development in shn mice were higher and shorter than those in sln. to elucidate these differences in the behavior of mammary tumorigenesis, the frequency of insertion of mammary tumor viral genes within the int-1 and int-2 regions in spontaneous mammary tumors from their two substrains, shn/s and sln/s, were compared. the frequency of provirus i ...19902156546
suppression of mouse mammary tumor proviral dna and protooncogene expression: association with nutritional regulation of mammary tumor development.chronic energy intake restriction (ceir) reduces mouse mammary tumor virus (mmtv)-induced mammary tumors in c3h/ou mice. fewer than 10% of c3h/ou mice developed mammary tumors during 88 wk of study when subjected to ceir regardless of calorie source (fat vs. carbohydrate). by contrast, 100% of mice fed ad libitum diets relatively high in fat or carbohydrate or a commercial diet developed tumors by 35-40 wk. mmtv proviral dna transcription was shown to be activated in spleen, liver, lung, kidney, ...19902157199
affinity of interactions between human glucocorticoid receptors and dna: at physiologic ionic strength, stable binding occurs only with dnas containing partially symmetric glucocorticoid response elements.sucrose density gradient shift assays were adapted to permit determination of the affinity of interaction between human glucocorticoid receptors (gr) and dna under conditions of dna excess. saturation analyses were performed to ascertain dissociation constants for the interaction of activated human gr with each of five dna fragments. centrifugation of gr-dna complexes on sucrose gradients under nearly isotonic salt conditions revealed similar affinities with dissociation constants in the range o ...19902168738
establishment of ddd/1-mtv-2/mtv-2, nu/nu and ddd/1-mtv-2/mtv-2, nu/+ mice: preliminary characterization in relation to mtv antigen expression and mammary tumorigenesis.to investigate the effects of the t-cell deprivation on viral mammary tumorigenesis, two double congenic mouse strains of the ddd genetic background, ddd/1-mtv-2/mtv-2, nu/nu and ddd/1-mtv-2/mtv-2, nu/+, were produced by the cross between ddd/1-mtv-2/mtv-2 (ddd-mtv-2) and ddd/1-nu/nu mice, followed by repeated intercross breedings. expression of the mouse mammary tumor virus (mtv)-gp52 antigen was demonstrated in the mammary glands of mice from 14 days on, in both -nu/nu and -nu/+ females. mamma ...19902168807
high level expression of wild type and variant mouse glucocorticoid receptors in chinese hamster ovary cells.we have isolated chinese hamster ovary (cho) cell lines expressing elevated levels of wild-type (w) and mutant forms of the glucocorticoid receptor (gr) using the technique of coamplification with a selectable dihydrofolate reductase (dhfr) cdna. a prominent doublet at 90/92 kilodaltons was observed by western blotting or labeling with [3h]-dexamethasone mesylate in extracts from cells transfected with w, the hormone binding mutant (na), and the dna binding mutant (nb). quantification of recepto ...19902157974
the proto-oncogene int-1 encodes a secreted protein associated with the extracellular matrix.the proto-oncogene int-1 plays an important role in mammary tumorigenesis when activated by proviral insertions of the mouse mammary tumor virus. in normal mouse tissues the gene is expressed in the embryonic neural tube, suggesting a developmental function, while in drosophila the homolog of int-1 is the segment polarity gene wingless. in order to study the protein products of int-1 we have derived fibroblast cell lines infected with multiple copies of a retroviral vector expressing int-1 cdna. ...19902158444
mechanism and biological significance of the ha-ras-induced activation of the na+/h(+)-antiporter.expression of the transforming ha-ras oncogene in mmtv-ltr transfected nih 3t3 cells leads to a growth factor independent activation of the na+/h(+)-antiporter. the activation of the antiporter is insensitive to the protein kinase inhibitor staurosporine and equally expressed in protein kinase c-depleted cells. it is concluded that the ha-ras induced activation of the antiporter occurs by a protein kinase c-independent mechanism. an inhibition of the na+/h(+)-antiporter by dimethylamiloride or a ...19902169700
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