Publications
| Title | Abstract | Year(sorted descending) Filter | PMID Filter |
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| conditionally adherent growth of serum-independent cho cells for automated drug screening and biopharmaceutical production. | ssf3 is a cho cell line adapted for growth in protein-free medium. it grows in suspension unless serum-derived attachment factors such as vitronectin are added to the medium. serum-independent cell lines, which adhere to the substrate after induction with dexamethasone or constitutively, were created by transfection with a human vitronectin gene under control of the mouse mammary tumor-virus promoter. substrate attachment and ssf3vn-cell spreading could be prevented with an rgd peptide (arginine ... | 1999 | 10516577 |
| rfg (ara70, ele1) interacts with the human androgen receptor in a ligand-dependent fashion, but functions only weakly as a coactivator in cotransfection assays. | abnormalities of the human androgen receptor (har) cause a range of clinical defects in male development. a large proportion of these mutations are single amino acid substitutions in the hormone-binding domain (hbd) that alter ar function by interfering with the capacity of the ar to bind androgen or to form stable hormone-receptor complexes. prior studies have suggested that the formation of such stable, active hormone-receptor complexes is a crucial step in the modulation of genes by the ar. i ... | 1999 | 10517667 |
| inhibition of histone deacetylation augments dihydrotestosterone induction of androgen receptor levels: an explanation for trichostatin a effects on androgen-induced chromatin remodeling and transcription of the mouse mammary tumor virus promoter. | the integrated mouse mammary tumor virus (mmtv) promoter has provided an excellent model system with which to study the impact of steroid hormones on transcriptional activation in the context of a defined chromatin structure. the hormone response element (hre) of this promoter is positioned on a phased nucleosome which becomes remodeled in response to steroids. one possible mechanism of chromatin remodeling by steroid receptors could involve recruitment of coactivators which alter the histone ac ... | 1999 | 10527637 |
| conditional modulation of glucocorticoid receptor activities by creb-binding protein (cbp) and p300. | coactivators of nuclear receptors are integral components of the signal transduction pathways of steroid hormones. here, we show that one of the major coactivators of the glucocorticoid receptor (gr), creb-binding protein (cbp), can also function conditionally as a negative regulator of its activities. indeed, cbp suppressed the responsiveness of the mouse mammary tumor virus (mmtv) promoter to dexamethasone in a dose-dependent fashion in hela and a204 cells. similarly, this protein suppressed t ... | 1999 | 10528999 |
| expression of mouse mammary tumor virus envelope protein does not prevent superinfection in vivo or in vitro. | inbred mice expressing endogenous mouse mammary tumor virus envelope proteins can be infected with exogenous virus, and the mammary tumors that develop in these mice usually have many proviruses integrated in their genomes, indicating that this virus is not subject to receptor interference. we show here that transgenic mice expressing an exogenous mouse mammary tumor virus (c3h) envelope protein can still be infected with this virus. moreover, cultured mammary gland cells expressing the mouse ma ... | 1999 | 10544114 |
| identification of a protein that recognizes a distal negative regulatory element within the mouse mammary tumor virus long terminal repeat. | the mouse mammary tumor virus (mmtv) long terminal repeat contains a distal negative regulatory element (dnre) that selectively represses activity of the proviral promoter in the absence of steroid hormone receptor-mediated activation. a protein, termed mmtv nre-binding protein 1 (mnbp-1), that recognizes long terminal repeat sequences between -433 and -418 was identified by gel electrophoresis mobility shift assays and methylation interference footprinting in nuclear extracts of hela and ltk(-) ... | 1999 | 10544147 |
| polycitone a, a novel and potent general inhibitor of retroviral reverse transcriptases and cellular dna polymerases. | polycitone a, an aromatic alkaloid isolated from the ascidian polycitor sp. exhibits potent inhibitory capacity of both rna- and dna-directed dna polymerases. the drug inhibits retroviral reverse transcriptase (rt) [i.e. of human immunodeficiency virus type 1 (hiv), murine leukaemia virus (mlv) and mouse mammary tumour virus (mmtv)] as efficiently as cellular dna polymerases (i.e. of both dna polymerases alpha and beta and escherichia coli dna polymerase i). the mode and mechanism of inhibition ... | 1999 | 10548537 |
| structure/function of the human glucocorticoid receptor: tyrosine 735 is important for transactivation. | ligand-induced activation of the glucocorticoid receptor (gr) is not well understood. the gr ligand-binding domain was modeled, based on homology with the progesterone receptor. tyrosine 735 interacts with the d ring of dexamethasone, and substitution of d ring functional groups results in partial agonist steroids with reduced ability to direct transactivation. loss of the tyr735 hydroxyl group by substitution to phenylalanine (tyr735phe) did not reduce ligand binding affinity [dissociation cons ... | 1999 | 10551779 |
| cd4+ t cell responses to cd40-deficient apcs: defects in proliferation and negative selection apply only with b cells as apcs. | during t-apc interactions in vivo, interfering with cd40-cd154 interactions leads to reduced t cell priming, defects in effector function, and, in some cases, t cell tolerance. as shown here, however, presentation of conventional peptide ags by cd40-deficient spleen apc in vitro leads to normal cd4+ t cell proliferative responses. by contrast, responses to the same peptides presented by purified b cells were markedly reduced in the absence of cd40. thus, the requirement for cd40-cd154 interactio ... | 1999 | 10553046 |
| involvement of notch1 in the development of mouse mammary tumors. | the mmtv/neu transgenic (tg) mice spontaneously develop mammary tumors stochastically after a long latent period, suggesting that the c-neu/erbb2 oncogene is not sufficient for tumor formation. to identify putative collaborator(s) of the c-neu/erbb2, we used the provirus insertional mutagenesis approach with mammary tumors arising in mmtv/neu tg mice infected with the mouse mammary tumor virus (mmtv). the notch1 gene was identified as a novel target for mmtv provirus insertional activation. in n ... | 1999 | 10557086 |
| mouse mammary tumor virus carrying a bacterial supf gene has wild-type pathogenicity and enables rapid isolation of proviral integration sites. | mouse mammary tumor virus (mmtv) has frequently been used as an insertional mutagen to identify provirally activated mammary proto-oncogenes. to expedite and facilitate the process of cloning mmtv insertion sites, we have introduced a bacterial supf suppressor trna gene into the long terminal repeat (ltr) of mmtv, thus allowing selection of clones containing it in lambda vectors bearing amber mutations. the presence of supf in the ltr should circumvent the screening process for proviral insertio ... | 1999 | 10559292 |
| wild-derived inbred mice have a novel basis of susceptibility to polyomavirus-induced tumors. | polyomavirus induces a broad array of tumors when introduced into newborn mice of certain standard inbred strains, notably those bearing the h-2(k) haplotype. susceptibility in these mice is conferred by an endogenous mouse mammary tumor virus superantigen (mtv-7 sag) that acts to delete t cells required for polyomavirus-induced tumor immunosurveillance. in the present study we show that mice of two wild-derived inbred strains, pera/ei (pe) and czech ii/ei (cz), are highly susceptible to polyoma ... | 1999 | 10559322 |
| a ligand binding domain mutation in the mouse glucocorticoid receptor functionally links chromatin remodeling and transcription initiation. | we utilized the mouse mammary tumor virus (mmtv) long terminal repeat (ltr) in vivo to understand how the interaction of the glucocorticoid receptor (gr) with a nucleosome-assembled promoter allows access of factors required for the transition from a repressed promoter to a derepressed, transcriptionally competent promoter. a mutation (c644g) in the ligand binding domain (lbd) of the mouse gr has provided information regarding the steps required in the derepression/activation process and in the ... | 1999 | 10567540 |
| accelerated mammary tumor development in mutant polyomavirus middle t transgenic mice expressing elevated levels of either the shc or grb2 adapter protein. | the grb2 and shc adapter proteins play critical roles in coupling activated growth factor receptors to several cellular signaling pathways. to assess the role of these molecules in mammary epithelial development and tumorigenesis, we have generated transgenic mice which individually express the grb2 and shc proteins in the mammary epithelium. although mammary epithelial cell-specific expression of grb2 or shc accelerated ductal morphogenesis, mammary tumors were rarely observed in these strains. ... | 1999 | 10567542 |
| expression of cre recombinase as a reporter of signal transduction in mammalian cells. | cell-based reporter assays, which rely on a reporter gene under the control of a regulated promoter, are widely used to screen chemical libraries for novel receptor ligands. here, we describe a reporter system that is based on ligand-induced dna recombination to express the reporter gene. this system converts a transient activation of a signal transduction pathway into an amplified, constitutive and heritable expression of the reporter gene. | 1999 | 10574783 |
| organogenic role of b lymphocytes in mucosal immunity. | follicle-associated epithelium (fae) in the intestinal peyer's patches contains m cells that deliver pathogens to organized lymphoid tissue. development of peyer's patches, fae, and m cells was found to be impaired in mice that had no b cells. transgenic expression of membrane-bound immunoglobulin m restored b cells and fae development. the lack of m cells abrogated infection with a milk-borne retrovirus. thus, in addition to secretion of antibodies and presentation of antigens, b cells are impo ... | 1999 | 10583962 |
| inhibition of heat shock factor activity prevents heat shock potentiation of glucocorticoid receptor-mediated gene expression. | using mouse l929 cells stably transfected with a glucocorticoid receptor (gr)-responsive murine mammary tumor virus-chloramphenicol acetyltransferase (mmtv-cat) reporter gene (lmcat2 cells), we have shown that cellular stress (heat or chemical shock) can cause a dramatic increase in the levels of dexamethasone (dex)-induced cat gene expression. we refer to this response as the heat shock potentiation effect, or hspe. as the cellular heat shock response also involves the activation of heat shock ... | 1999 | 10590836 |
| mouse models for breast cancer. | 1999 | 11250684 | |
| mammary gland expression of mouse mammary tumor virus is regulated by a novel element in the long terminal repeat. | mouse mammary tumor virus (mmtv) infects both lymphoid tissue and lactating mammary gland during its infectious cycle, but some endogenous mmtvs are transcribed only in lymphoid cells. we found a lymphoid cell-specific endogenous mmtv that was converted to a milk-borne, infectious virus through recombination with an exogenously transmitted mmtv. the changed expression pattern correlated with the alteration of a single base pair in the long terminal repeat of the lymphoid cell-specific virus. tra ... | 1999 | 9847341 |
| systemic antibodies can inhibit mouse mammary tumor virus-driven superantigen response in mucosa-associated lymphoid tissues. | many mucosal pathogens invade the host by initially infecting the organized mucosa-associated lymphoid tissue (o-malt) such as peyer's patches or nasal cavity-associated lymphoid tissue (nalt) before spreading systemically. there is no clear demonstration that serum antibodies can prevent infections in o-malt. we have tested this possibility by using the mouse mammary tumor virus (mmtv) as a model system. in peripheral lymph nodes or in peyer's patches or nalt, mmtv initially infects b lymphocyt ... | 1999 | 9882389 |
| kinetic properties and stereospecificity of the monomeric dutpase from herpes simplex virus type 1. | kinetic properties of the monomeric enzyme dutpase from herpes simplex virus type 1 (hsv) were investigated and compared to those previously determined for homotrimeric dutpases of bacterial and retroviral origins. the hsv and escherichia coli dutpases are equally potent as catalysts towards the native substrate dutp with a kcat/k(m) of about 10(7) m(-1) s(-1) and a k(m) of 0.3 microm. however, the viral enzymes are less specific than the bacterial enzyme. the hsv and e. coli dutpases show the s ... | 1998 | 9883909 |
| cytolytic activities of il-2 activated nk cells from mmtv/v-ha-ras transgenic oncomice during tumor progression. | il-2 activated natural killer (a-nk) cells have the capacity to infiltrate metastatic tumors and lyse tumor cells. nevertheless, adoptive immunotherapy with lymphokine-activated killer cells has been only modestly effective in the clinic and has not routinely provided long-term survival in patients with established cancer metastases. this may indicate the need for more carefully investigating the role of effector cells of the immune response, including a-nk cells, in models of tumor progression. ... | 1998 | 9891221 |
| rna polymerase ii transcription complex assembly in nuclear extracts. | in vitro transcription systems based on nuclear extracts of eukaryotic cells continue to be valuable experimental systems for assessing function of promoter sequences and defining new activities involved in transcription complex assembly and activity, but many aspects of such systems have not been experimentally examined. here, transcription complex assembly on the promoter from the long terminal repeat of mouse mammary tumor virus was assessed in vitro with a transcription system derived from n ... | 1998 | 9840811 |
| mmtv-fgf8 transgenic mice develop mammary and salivary gland neoplasia and ovarian stromal hyperplasia. | prior studies have identified fibroblast growth factor-8 (fgf8) as a possible proto-oncogene in mouse mammary tumorigenesis. we now report on the generation of two types of fgf8 transgenic mice that each utilize the mouse mammary tumor virus (mmtv) promoter. the first transgene (mmtv-fgf8b) results in the overexpression of the fgf8b isoform exclusively. male and female mmtv-fgf8b transgenic mice are viable and fertile. rna for fgf8b is detected in mammary gland and salivary gland tissues of tran ... | 1998 | 9840935 |
| the matrix metalloproteinase matrilysin influences early-stage mammary tumorigenesis. | overexpression of the epithelial specific matrix metalloproteinase matrilysin (mat) has been correlated with enhanced tumorigenicity and tumor cell invasion using in vitro model systems. we have determined the effects of mat expression on the development of mammary tumorigenesis using transgenic mice that express human mat under the control of the mouse mammary tumor virus (mmtv)-long terminal repeat promoter/enhancer. examination of mammary glands from multiparous mmtv-mat animals revealed the ... | 1998 | 9850086 |
| overexpression of vegf in testis and epididymis causes infertility in transgenic mice: evidence for nonendothelial targets for vegf. | vascular endothelial growth factor (vegf) is a key regulator of endothelial growth and permeability. however, vegf may also target nonendothelial cells, as vegf receptors and responsiveness have been detected for example in monocytes, and high concentrations of vegf have been reported in human semen. in this work we present evidence that overexpression of vegf in the testis and epididymis of transgenic mice under the mouse mammary tumor virus (mmtv) ltr promoter causes infertility. the testes of ... | 1998 | 9852161 |
| telomere length, telomerase activity and telomerase rna expression during mouse mammary tumor progression. | to investigate the roles of telomere length (mean length of the terminal restriction fragments; trfs), telomerase activity (ta) and telomerase rna (mtr) expression in relation to mouse mammary tumor progression, we examined a pregnancy-dependent mouse mammary tumor line (tpdmt-4) and its four autonomous sublines (t4-oi320: non-metastatic; and t4-oi165, -oi96, and -oi145: artificial metastatic) of ddd/1 mouse origin, and an autonomous growing mammary tumor (jyg-mc) showing spontaneous lung metast ... | 1998 | 9857231 |
| oligoribonucleotides containing 8-oxo-7,8-dihydroguanosine and 8-oxo-7,8-dihydro-2'-o-methylguanosine: synthesis and base pairing properties. | 7,8-dihydroguanosine(8-oxog) and 7,8-dihydro-2'-o-methylguanosine (8-oxog-me) were chemically synthesized. oligoribonucleotides which contain 8-oxog or 8-oxog-me were synthesized. incorporation of nucleotides opposite 8-oxog and 8-oxog-me with dntp by mmlv reverse transcriptase during cdna synthesis was characterized. | 1998 | 9871516 |
| novel tools for production and purification of recombinant adenoassociated virus vectors. | standard protocols for the generation of adenoassociated virus type 2 (aav-2)-based vectors for human gene therapy applications require cotransfection of cells with a recombinant aav (raav) vector plasmid and a packaging plasmid that provides the aav rep and cap genes. the transfected cells must also be overinfected with a helper virus, e.g., adenovirus (ad), which delivers multiple helper functions necessary for raav production. therefore, raav stocks produced using these protocols are contamin ... | 1998 | 9874273 |
| redundant proteolytic activation of a viral superantigen. | proteolytic activation of viral superantigens (vsags)4 expressed in chinese hamster ovary (cho) cells is required for t cell stimulation, and is mediated primarily by the protein convertase (pc) furin. three pc recognition sites are highly conserved in vsags, but it was not known which sites are required for pc dependent vsag activation. moreover, because the pc recognition sites are not conserved in all functional vsags it was possible that activation could occur by processing at any of several ... | 1998 | 9881685 |
| mouse mammary tumor virus and its interaction with the immune system. | mouse mammary tumor virus (mmtv) is a retrovirus that is transmitted through milk to offspring. gut-associated b cells are the first cells to be infected during virus transmission, and these cells present a virus-encoded superantigen to cognate t cells. this allows mmtv to replicate and amplify in activated lymphocytes and ultimately results in virus transmission to the mammary epithelial cells. because the superantigen has profound effects on the t cell repertoire and because mmtv replicates in ... | 1998 | 9479582 |
| synergistic enhancement of prb-mediated ru486 and r5020 agonist activities through cyclic adenosine 3',5'-monophosphate represents a delayed primary response. | activators of protein kinase a have been shown to affect the transactivation potential of progestins and antiprogestins. to analyze the mechanisms and factors involved, we have created hela and cv1 cell clones stably expressing isoform b of progesterone receptor. in the hela cell background, the progesterone antagonist ru486 significantly induces progesterone-regulatable reporter genes, and this agonistic effect is synergistically enhanced by elevating camp or through overexpression of protein k ... | 1998 | 9482668 |
| prolonged glucocorticoid exposure dephosphorylates histone h1 and inactivates the mmtv promoter. | glucocorticoids rapidly induce transcription from the mouse mammary tumour virus (mmtv) promoter via a glucocorticoid receptor (gr)-mediated chromatin disruption event. this remodelling of chromatin is transient such that upon prolonged exposure to hormone the promoter becomes refractory to glucocorticoids. we demonstrate that this refractory state requires the continual presence of hormone and can be reversed by its removal. our experiments show that the promoter is inactivated via a mechanism ... | 1998 | 9482742 |
| a full-length notch1 allele is dispensable for transformation associated with a provirally activated truncated notch1 allele in moloney mulv-infected mmtv(d)/myc transgenic mice. | the notch1 gene was previously found to be targetted by provirus insertion in a high proportion of t-cell lymphomas arising in moloney mulv-inoculated mmtv(d)/myc transgenic mice. proviral activation of notch1 was associated with overexpression of truncated notch1, deleted of the sequences coding for the extracellular domain. the high levels of truncated notch1 rna and proteins in these tumors are thought to be involved in the oncogenic transformation. however, in addition to these truncated rna ... | 1998 | 9484841 |
| regulation of na-k-atpase gene expression by hyperoxia in mdck cells. | na-k-atpase plays a central role in a variety of physiological processes, including ion transport and regulation of cell volume. our previous data showed that hyperoxia increased the expression of na-k-atpase alpha 1 and beta 1 mrna in lung type ii cells. we similarly show that hyperoxia (> or = 95% o2 for 24-48 h) increased steady-state mrna levels in both na-k-atpase subunits in madin-darby canine kidney (mdck) cells. the mechanism of gene regulation by hyperoxia was assessed. stability of the ... | 1998 | 9486124 |
| mutational analysis of the rna pseudoknot involved in efficient ribosomal frameshifting in simian retrovirus-1. | mutational effects on frameshifting efficiency of the rna pseudoknot involved in ribosomal frameshifting in simian retrovirus-1 (srv-1) have been investigated. the primary sequence and the proposed secondary structure of the srv-1 pseudoknot are similar to those of other efficient frameshifting pseudoknots in mouse mammary tumor virus (mmtv) and feline immunodeficiency virus (fiv), where an unpaired adenine nucleotide intercalates between stem 1 and stem 2. in srv-1 pseudoknot, the adenine nucle ... | 1998 | 9490779 |
| positioning and stability of nucleosomes on mmtv 3'ltr sequences. | uniquely positioned nucleosomes were mapped in vitro on mouse mammary tumor 3' long terminal repeat (mmtv 3'ltr) dna at base-pair resolution. nucleosome a assembly was strongly favored over nucleosome b, and heating of each as a mononucleosome caused migration to the ends of the dna fragment at a unique rate. taken together with dna sequence analysis, this suggests why mmtv 3'ltv nucleosome positions reported upstream of vector-derived sequences conflict and also how flanking genomic sequences c ... | 1998 | 9466921 |
| tumour therapy in mice using adenovirus vectors expressing human tnfa. | induction of systemic toxicity is a major factor limiting the use of tnfa in tumour therapy. the local expression of tnfa from ad vector infected tumour cells, might result in reduced systemic toxicity and induce an enhanced local antitumour response. two adenoviral vectors expressing human tnfa were constructed for use in tumour immunotherapy, one utilizing the hcmv promoter (ad-hcmv-tnf) and the second utilizing the mcmv promoter (ad-mcmv-tnf). both vectors induced the secretion of htnfa from ... | 1998 | 9472086 |
| transposon-mediated random insertions and site-directed mutagenesis prevent the trafficking of a mouse mammary tumor virus superantigen. | mouse mammary tumor viruses (mmtvs) encode superantigens (sags) which are critical to the life cycle of infectious virus and can mediate extensive deletion of t lymphocytes when expressed by endogenous proviruses. little is known about the structure, intracellular trafficking, or nature of sag association with major histocompatibility (mhc) class ii products. in order to gain a better understanding of sag structure-function relationships, we extensively mutagenized this type ii glycoprotein usin ... | 1998 | 9568034 |
| modulation of hormone-dependent glucocorticoid receptor function using a tetracycline-regulated expression system. | the glucocorticoid receptor (gr) is a ligand-dependent transcription factor capable of stimulating and inhibiting the expression of target genes. to better understand the biological action of glucocorticoids and the function of gr, we have utilized the tetracycline (tc)-regulated mammalian expression system to develop a novel cell line, e8.2/gr3, derived from gr null mouse l929 fibroblasts, that exhibits conditional expression of rat gr. the intracellular concentration of rgr in e8.2/gr3 cells-- ... | 1998 | 9569005 |
| mutational and functional analysis of the c-terminal region of the c3h mouse mammary tumor virus superantigen. | the mouse mammary tumor virus (mmtv) encodes within the u3 region of the long terminal repeat (ltr) a protein known as the superantigen (sag). sag is needed for the efficient transmission of milk-borne virus from the gut to target tissue in the mammary gland. mmtv-infected b cells in the gut express sag as a type ii transmembrane protein that is recognized by the variable region of particular beta chains (vbeta) of the t-cell receptor (tcr) on the surface of t cells. recognition of sag by partic ... | 1998 | 9573239 |
| identification and characterization of a tannic acid-responsive negative regulatory element in the mouse mammary tumor virus promoter. | tannic acid, which comprises polyphenolic compounds from tea leaves, suppresses the glucocorticoid-induced gene expression of mouse mammary tumor virus (mmtv) integrated into 34i cells. to investigate whether this suppression is due to promoter responsiveness to tannic acid, we performed chloramphenicol acetyltransferase analysis transfecting a mmtv promoter containing a chloramphenicol acetyltransferase expression vector into mouse fibroblast l929 cells. deletion analysis of the promoter region ... | 1998 | 9575208 |
| recruitment of octamer transcription factors to dna by glucocorticoid receptor. | glucocorticoid receptor (gr) and octamer transcription factors 1 and 2 (oct-1/2) interact synergistically to activate the transcription of mouse mammary tumor virus and many cellular genes. synergism correlates with cooperative dna binding of the two factors in vitro. to examine the molecular basis for these cooperative interactions, we have studied the consequences of protein-protein binding between gr and oct-1/2. we have determined that gr binds in solution to the octamer factor pou domain. b ... | 1998 | 9584182 |
| the position and length of the steroid-dependent hypersensitive region in the mouse mammary tumor virus long terminal repeat are invariant despite multiple nucleosome b frames. | stimulation of the mouse mammary tumor virus with steroids results in the generation of a dnase i-hypersensitive region (hsr) spanning the hormone responsive element (hre) in the long terminal repeat. restriction enzymes were used to characterize the accessibility of various sites within the hsr of mouse mammary tumor virus long terminal repeat-reporter constructions in four different cell lines. the glucocorticoid-dependent hsr was found to span minimally 187 bases, a stretch of dna longer than ... | 1998 | 9584204 |
| chromatin remodelling by the glucocorticoid receptor requires the brg1 complex. | the assembly of transcriptional regulatory dna sequences into chromatin plays a fundamental role in modulating gene expression. the promoter of the mouse mammary-tumour virus (mmtv) is packaged into a regular array of nucleosomes when it becomes stably integrated into mammalian chromosomes, and has been used to investigate the relationship between chromatin architecture and transcriptional activation by the hormone-bound glucocorticoid and progesterone receptors. in mammalian cells that express ... | 1998 | 9590696 |
| characterization of fatty acid synthase in cell lines derived from experimental mammary tumors. | the lipogenic enzyme fatty acid synthase (fas) is elevated in various human primary cancers and certain human cancer cell lines. fas overexpression in human neoplasia has clinical relevance because of its association with tumor aggression and potential chemotherapeutic intervention. here, we surveyed fas in cell lines established from normal murine mammary epithelium (nmumg) and from mammary tumors induced by either rodent polyoma (py) virus or murine mammary tumor virus (mmtv). western blotting ... | 1998 | 9593836 |
| viral superantigen-induced negative selection of tcr transgenic cd4+ cd8+ thymocytes depends on activation, but not proliferation. | t-cell negative selection, a process by which intrathymic immunological tolerance is induced, involves the apoptosis-mediated clonal deletion of potentially autoreactive t cells. although different experimental approaches suggest that this process is triggered as the result of activation-mediated cell death, the signal transduction pathways underlying this process is not fully understood. in the present report we have used an in vitro system to analyze the cell activation and proliferation requi ... | 1998 | 9596673 |
| polyamines induce malignant transformation in cultured nih 3t3 fibroblasts. | previous studies have demonstrated that polyamines accumulate in cancer cells and that overproduction of ornithine decarboxylase (odc), which catalyzes polyamine synthesis, elicits the acquisition of the transformed phenotype. however, it was not clear whether the overexpression of odc and the accumulation of polyamines are only innocent by-products of the transformation process. in this study we demonstrate that polyamines as such, may play a crucial role in malignant transformation. the system ... | 1998 | 9597759 |
| human progesterone receptor a and b isoforms in cho cells. ii. comparison of binding, transactivation and ed50 values of several synthetic (anti)progestagens in vitro in cho and mcf-7 cells and in vivo in rabbits and rats. | the human progesterone receptor a and b isoforms (hpr-a and hpr-b) were stably transfected in chinese hamster ovary (cho) cells in the presence or absence of the mouse mamma tumor virus (mmtv) promoter and luciferase (luc) reporter gene. in this way four stably transfected cho cell lines, i.e. hpr-a, hpr-b, hpr-a-mmtv-luc and hpr-b-mmtv-luc cells, were prepared. hpr-a and -b isoforms were compared by binding and transactivation analysis for 14 progestagens and 7 antiprogestagens. thereby org 205 ... | 1998 | 9605410 |
| functional activities of the a and b forms of the human androgen receptor in response to androgen receptor agonists and antagonists. | the androgen receptor (ar) is present in many cells in two forms. the b form migrates with an apparent mass of 110 kda and constitutes more than 80% of the immunoreactive receptor in most cell types. the a form of the ar migrates with an apparent mass of 87 kda, appears to derive from internal translation initiation at methionine-188 in the ar open-reading frame, and usually constitutes 20% or less of the immunoreactive ar present. previous experiments designed to examine the functional capacity ... | 1998 | 9605928 |
| auxiliary downstream elements are required for efficient polyadenylation of mammalian pre-mrnas. | we have previously identified a g-rich sequence (grs) as an auxiliary downstream element (aux dse) which influences the processing efficiency of the sv40 late polyadenylation signal. we have now determined that sequences downstream of the core u-rich element (ure) form a fundamental part of mammalian polyadenylation signals. these novel aux dses all influenced the efficiency of 3'-end processing in vitro by stabilizing the assembly of cstf on the core downstream ure. three possible mechanisms by ... | 1998 | 9611233 |
| negative regulation of the rat glutathione s-transferase a2 gene by glucocorticoids involves a canonical glucocorticoid consensus sequence. | glucocorticoids (gcs) repress both basal and polyaromatic hydrocarbon-induced expression of the glutathione s-transferase ya1 gene (gsta2) in isolated rat hepatocytes and rat liver in vivo. transient transfection experiments with hepg2 cells were used to identify gc-responsive elements (gres). with cotransfected gc receptor, chloramphenicol acetyltransferase (cat) constructs containing a palindromic gre (pgre) and three gre hexanucleotide half-sites between -1.6 and -1.1 kb of the 5'-flanking re ... | 1998 | 9614203 |
| in vitro and in vivo antisense-mediated growth inhibition of a mammary adenocarcinoma from mmtv-neu transgenic mice. | oncogene-bearing transgenic mice develop various kinds of tumors depending on both the regulatory sequences and the specific oncogene used. these mice not only help to clarify the pathogenetic pathways leading to tumor formation, but can also be useful as models to test novel therapeutic strategies, including gene therapy. we have previously reported the establishment of an mmtv-neu (erbb-2) transgenic mouse lineage, in which 100% of females develop breast tumors with many features similar to th ... | 1998 | 9614559 |
| the mouse mammary tumour virus promoter positioned on a tetramer of histones h3 and h4 binds nuclear factor 1 and otf1. | modulation of eukaryotic gene expression is influenced by the organization of regulatory dna-elements in chromatin. the mouse mammary tumor virus (mmtv) promoter exhibits regularly positioned nucleosomes that reduce the accessibility of the binding sites for sequence-specific transcription factors, in particular nuclear factor (nf1). hormonal induction of the mmtv promoter is accompanied by remodeling of the nucleosomal structure, but the biochemical nature of these structural changes is unknown ... | 1998 | 9614938 |
| regulatory cd4 t cells: expression of il-2r alpha chain, resistance to clonal deletion and il-2 dependency. | we recently characterized a cd4+ t cell population expressing the il-2r alpha chain (cd25), producing il-10 and resisting clonal deletion induced by viral superantigen (vsag) encoded by mouse mammary tumor virus [mmtv(sw)]. we now report that these apoptosis-resistant cells are generated in the thymus but not from the immature cd4+ cd8+ thymocytes. they migrate from the thymus and are found in the periphery from at least the 10th day of life, after which they expand with the same kinetics in nor ... | 1998 | 9620592 |
| mouse mammary tumor virus superantigen expression in b cells is regulated by a central enhancer within the pol gene. | expression of mouse mammary tumor virus (mmtv)-encoded superantigens in b lymphocytes is required for viral transmission and pathogenesis. the mechanism of superantigen expression from the viral sag gene in b cells is largely unknown, due to problems with detection and quantification of these low-abundance proteins. we have established a sensitive superantigen-luciferase reporter assay to study the expression and regulation of the mmtv sag gene in b-cell lymphomas. the regulatory elements for re ... | 1998 | 9621071 |
| a dual-luciferase reporter system for studying recoding signals. | a new reporter system has been developed for measuring translation coupling efficiency of recoding mechanisms such as frameshifting or readthrough. a recoding test sequence is cloned in between the renilla and firefly luciferase reporter genes and the two luciferase activities are subsequently measured in the same tube. the normalized ratio of the two activities is proportional to the efficiency with which the ribosome "reads" the recoding signal making the transition from one open reading frame ... | 1998 | 9630253 |
| genetic modulation of neu proto-oncogene-induced mammary tumorigenesis. | modulation of oncogene-induced carcinogenesis by secondary mutation or genetic background may be an important factor in determining the expression of the tumor phenotype. we have investigated the role of loss of function mutations and strain-specific genetic elements in the modulation of oncogene-induced breast cancer using a murine model. fvb female mice transgenic for the rat neu proto-oncogene [mouse mammary tumor virus (mmtv)-neu] developed mammary tumors between 7 and 12 months of age, wher ... | 1998 | 9635596 |
| disregulation of ocular morphogenesis by lens-specific expression of fgf-3/int-2 in transgenic mice. | fgf-3, originally named int-2, was discovered as an oncogene frequently activated in mammary carcinomas resulting from the chromosomal integration of the mouse mammary tumor virus (mmtv). int-2 was later designated fgf-3 based on sequence homology with other members of the fibroblast growth factor (fgf) family. fgf-1 is the prototypical member of the fgf family, and is the only family member which activates all known fgf receptor isoforms. transgenic mice expressing in the lens a form of fgf-1 e ... | 1998 | 9640329 |
| myc/p53 interactions in transgenic mouse mammary development, tumorigenesis and chromosomal instability. | we have examined defects in mammary development and tumorigenesis in a transgenic model expressing the c-myc gene under the mmtv-ltr promoter. the stochastic tumors which arise from hyperplastic ductal and lobular lesions in this model are characterized by high rates both of apoptosis and of chromosomal instability. since the p53 gene product is thought to be central in the maintenance of genomic integrity, in part due to its ability to induce apoptosis in cells harboring dna damage, we examined ... | 1998 | 9652742 |
| a role for herpesvirus saimiri orf14 in transformation and persistent infection. | the product of open reading frame 14 (orf14) of herpesvirus saimiri (hvs) exhibits significant homology with mouse mammary tumor virus superantigen. orf14 encodes a 50-kda secreted glycoprotein, as shown previously (z. yao, e. maraskovsky, m. k. spriggs, j. i. cohen, r. j. armitage, and m. r. alderson, j. immunol. 156:3260-3266, 1996). orf14 expressed from recombinant baculovirus powerfully induces proliferation of cd4-positive cells originating from several different species. to study the role ... | 1998 | 9658125 |
| calcium/calmodulin kinase inhibitors and immunosuppressant macrolides rapamycin and fk506 inhibit progestin- and glucocorticosteroid receptor-mediated transcription in human breast cancer t47d cells. | the effects of immunosuppressants and inhibitors of specific calcium/calmodulin kinase (camk) of types ii and iv on progestin/glucocorticosteroid-induced transcription were studied in two human stably transfected breast cancer t47d cell lines. the lines contain the chloramphenicol acetyl transferase (cat) gene under control either of the mouse mammary tumor virus promoter (t47d-mmtv-cat), or the minimal promoter containing five glucocorticosteroid/progestin hormone response elements [t47d-(gre)5 ... | 1998 | 9658403 |
| nuclear factor i (nfi) isoforms differentially activate simple versus complex nfi-responsive promoters. | promoter-specific differences in the function of transcription factors play a central role in the regulation of gene expression. we have measured the maximal transcriptional activation potentials of nuclear factor i (nfi) proteins encoded by each of the four identified nfi genes (nfi-a, -b, -c, and -x) by transient transfection in jeg-3 cells using two model nfi-dependent promoters: 1) a simple chimeric promoter containing a single nfi-binding site upstream of the adenovirus major late promoter ... | 1998 | 9660824 |
| permanent alteration of endogenous gangliosides in neuroblastoma cells by stable transfection with antisense vector. | 1998 | 9668392 | |
| loss of endogenous mouse mammary tumor virus superantigen increases tumor resistance. | from a cross between a tumor-susceptible mouse strain (dba/2; d) and a tumor-resistant mhc-identical strain (b10.d2; d2) new recombinant inbred mouse strains were established over many generations of inbreeding and tumor resistance selection. since resistance to the highly metastatic dba/2 lymphoma variant esb had an immunologic basis, and the two parental strains differed in endogenous viral superantigens (vsags), dna of three d2 x d recombinant inbred mouse lines was typed for endogenous mouse ... | 1998 | 9670928 |
| reduced metastasis of polyoma virus middle t antigen-induced mammary cancer in plasminogen-deficient mice. | to investigate the role of plasmin(ogen) in mammary tumor development and progression, plasminogen-deficient mice were crossed with transgenic mice expressing polyoma middle t antigen under the control of the mouse mammary tumor virus long terminal repeat. virgin females carrying the polyoma middle t antigen uniformly developed multiple, bilateral mammary tumors, regardless of the presence or absence of circulating plasminogen. both the age at which these tumors became palpable and subsequent tu ... | 1998 | 9671388 |
| agonist-specific modulation of glucocorticoid receptor-mediated transcription by immunosuppressants. | although the immunosuppressive drugs fk506, rapamycin and cyclosporin a have been reported to potentiate transcriptional activation mediated by a non-saturating concentration of the glucocorticoid receptor agonist dexamethasone, the precise mechanism(s) underlying these responses remains unclear. the murine l-929-derived lmcat cell line stably transfected with the mouse mammary tumor virus promoter-chloramphenicol acetyl transferase reporter gene construct was utilized in the present study to fu ... | 1998 | 9685211 |
| assembly of mmtv promoter minichromosomes with positioned nucleosomes precludes nf1 access but not restriction enzyme cleavage. | to generate long arrays of nucleosomes within a topologically defined chromatin domain we have assembled minichromosomes on negatively supercoiled plasmid dna with extracts from drosophila preblastoderm embryos. these minichromosomes are dynamic substrates for energy-dependent nucleosome remodeling machines that facilitate the binding of various transcription factors but do not exhibit nucleosome positioning. in contrast, if such minichromosomes include the mouse mammary tumour virus (mmtv) prom ... | 1998 | 9685480 |
| sequence-specific binding of ku autoantigen to single-stranded dna. | glucocorticoid-induced transcription of mouse mammary tumor virus is repressed by ku antigen/dna-dependent protein kinase (dna-pk) through a dna sequence element (nre1) in the viral long terminal repeat. nuclear factors binding to the separated single strands of nre1 have been identified that may also be important for transcriptional regulation through this element. we report the separation of the upper-stranded nre1 binding activity in jurkat t cell nuclear extracts into two components. one com ... | 1998 | 9694826 |
| mapping of a mouse mammary tumor virus integration site by retroviral ltr--arbitrary polymerase chain reaction. | the de novo integration of retroviral genomes within the mammalian genome is believed to contribute to the tumorigenic process. integration may result in the disruption or inappropriate transcription of key regulatory genes. we describe the application of an arbitrarily primed pcr method for the mapping and cloning of genomic integration sites of the mouse mammary tumor virus (mmtv). we have amplified dna sequences between a selected retroviral mmtv-ltr and random sites in the 3' flanking dna. u ... | 1998 | 9696128 |
| preactivation of b lymphocytes does not enhance mouse mammary tumor virus infection. | we investigated whether mouse mammary tumor virus (mmtv) favors preactivated or naive b cells as targets for efficient infection. we have demonstrated previously that mmtv activates b cells upon infection. here, we show that polyclonal activation of b cells leads instead to lower infection levels and attenuated superantigen-specific t-cell responses in vivo. this indicates that naive small resting b cells are the major targets of mmtv infection and that the activation induced by mmtv is sufficie ... | 1998 | 9696877 |
| atp-mediated activation of rna polymerase ii transcription complexes. | transcription initiation by rna polymerase ii is a complex, multistep process that minimally involves transcription complex assembly, open complex formation, and promoter clearance. hydrolysis of the beta--gamma phosphoanhydride bond of atp has previously been shown to be required for open complex formation, as well as for the phosphorylation of the carboxy-terminal domain of the largest subunit of rna polymerase ii. the observation that atp-dependent activation of transcription complexes can be ... | 1998 | 9699480 |
| intranuclear trafficking and gene targeting by members of the steroid/nuclear receptor superfamily. | upon binding to regulatory elements in mammalian chromosomes, steroid receptors induce specific transitions in the nucleoprotein structure of the template. these transitions reflect, in part, the reorganization of chromatin structure to permit interaction of secondary factors with target sequences in promoter regulatory regions. steroid receptors represent a class of transcriptional activators that are able to interact with repressed nucleoprotein templates and recruit necessary activities for c ... | 1998 | 9699865 |
| dexamethasone and triamcinolone acetonide accumulation in mouse fibroblasts is differently modulated by the immunosuppressants cyclosporin a, fk506, rapamycin and their analogues, as well as by other p-glycoprotein ligands. | in mouse fibroblasts (lmcat cells) stably transfected with the reporter gene chloramphenicol acetyl transferase under the control of the mouse mammary tumor virus promoter (mmtv-cat), cyclosporin a (csa), fk506, and rapamycin (rap) at micromolar concentrations potentiate dexamethasone- (dex) induced cat gene activity in a dose-dependent way (renoir j.-m., mercier-bodard c., hoffmann k., le bihan s., ning y. m., sanchez e. r., handschumacher r. e. and baulieu e. e., proc. natl. acad. sci. u.s.a., ... | 1998 | 9712407 |
| functional interactions of the af-2 activation domain core region of the human androgen receptor with the amino-terminal domain and with the transcriptional coactivator tif2 (transcriptional intermediary factor2). | previous studies in yeast and mammalian cells showed a functional interaction between the amino-terminal domain and the carboxy-terminal, ligand-binding domain (lbd) of the human androgen receptor (ar). in the present study, the ar subdomains involved in this in vivo interaction were determined in more detail. cotransfection experiments in chinese hamster ovary (cho) cells and two-hybrid experiments in yeast revealed that two regions in the nh2-terminal domain are involved in the functional inte ... | 1998 | 9717843 |
| [requirement of class ii and membrane proximal region of mouse mammary tumor virus superantigen (mtv sag) in mtv7 sag presentation]. | although in some cases superantigens (sags) have been shown to bind directly to t cell receptor (tcr) in the absence of mhc molecules, the precise role of mhc class ii in sag presentation to t cells is not thoroughly understood. in particular, it is still not known whether mhc class ii is a mere transporter of mouse mammary tumor virus (mtv) sag to the cell surface or an essential component complexed with sags for tcr triggering. in this study, we found that mhc class ii negative b cell line tra ... | 1998 | 9719947 |
| resistance of human leukemic cem-c1 cells is overcome by synergism between glucocorticoid and protein kinase a pathways: correlation with c-myc suppression. | glucocorticoids (gcs) induce apoptosis in lymphoid cells that contain functional gc receptors (grs). however, gc resistance often is seen in cells with demonstrable grs; one such line is cem-c1. we have tested the hypothesis that positive interactions between gc and cyclic amp (camp) regulate gc actions in cem clones. treatment of both gc-resistant cem-c1 [resistant to 1 microm dexamethasone (dex)] and the sensitive sister clone, cem-c7 (approximately 65% cell death with 20 nm dex, approximately ... | 1998 | 9721879 |
| modulation of disease by superantigens. | increasing evidence suggests that bacterial and viral superantigens are involved in immune-mediated disease. studies using an animal model for multiple sclerosis show that superantigens can induce relapses and bring into play autoreactive t cells with restricted usage of t cell receptor v beta families that may be indirectly involved in the initial episode of disease. this may also involve epitope spreading. superantigens have also been implicated in other autoimmune diseases such as rheumatoid ... | 1998 | 9722924 |
| mutation of aspartate-233 to valine in mouse ornithine decarboxylase reduces enzyme activity. | ornithine decarboxylase is the first and key enzyme in mammalian polyamine biosynthesis. all eukaryotic ornithine decarboxylases contain several highly conserved regions and the amino acid residues 232-238 form one of the most highly conserved sequences. this region contains a glycine-rich sequence typically found in a number of pyridoxal 5'-phosphate-dependent or nucleotide-binding proteins. we mutated aspartate-233 which is the only acidic residue within this region to valine. this mutation ca ... | 1998 | 9722985 |
| b and t cells are required for mouse mammary tumor virus spread within the mammary gland. | mouse mammary tumor virus (mmtv) is an infectious retrovirus transmitted through milk from mother to newborns. mmtv encodes a superantigen (sag) whose activity is indispensable for the virus life cycle, since a genetically engineered virus with a mutation in the sag gene neither amplified in cells of the immune system of suckling pups nor infected their mammary glands. when wild-type mmtv was injected directly into the mammary glands of uninfected pubescent mice, their lymphoid as well as mammar ... | 1998 | 9725233 |
| mechanism of hiv pathogenesis: role of superantigens in disease. | initial infection with human immunodeficiency virus (hiv) results in a burst of viremia and an ensuing spread of virus to secondary lymphoid organs, after which a "latency" period occurs with little or no virus detectable in the circulation. the term latent period has been shown to be a misnomer, because substantial viral replication occurs during this time in lymph nodes, although clinically there appears to be few symptoms of disease. however, a telling indicator of active infection during thi ... | 1998 | 9727632 |
| induction of endogenous mammary tumor virus in lymphocytes infected with murine acquired immunodeficiency syndrome virus. | mice infected with murine acquired immunodeficiency syndrome (maids) virus developed lymphoadenopathy and profound immunodeficiency. concomitantly the expression of endogenous mammary tumor virus (mtv) mrna increased significantly, especially for the 1.7-kb 3' open reading frame (orf) mrna encoding mtv superantigen. b cell lines that are established from maids mice and exhibit superantigen activity also express a high level of 1.7-kb endogenous mtv and mrna. infection of a b cell tumor line in v ... | 1998 | 9732700 |
| the secondary structure of the r region of a murine leukemia virus is important for stimulation of long terminal repeat-driven gene expression. | in addition to their role in reverse transcription, the r-region sequences of some retroviruses affect viral transcription. the first 28 nucleotides of the r region within the long terminal repeat (ltr) of the murine type c retrovirus sl3 were predicted to form a stem-loop structure. we tested whether this structure affected the transcriptional activity of the viral ltr. mutations that altered either side of the stem and thus disrupted base pairing were generated. these decreased the level of ex ... | 1998 | 9733816 |
| purification and characterization of a cellular protein that binds to the downstream activation sequence of the strict late ul38 promoter of herpes simplex virus type 1. | previous work on the strict late (gamma) ul38 promoter of herpes simplex virus type 1 identified three cis-acting elements required for wild-type levels of transcription: a tata box at -31, a consensus mammalian initiator element at the transcription start site, and a downstream activation sequence (das) at +20 to +33. das is found in similar locations on several other late promoters, suggesting an important regulatory role in late gene expression. in this communication, we further characterize ... | 1998 | 9733860 |
| expression of ovine insulin-like growth factor-1 (igf-1) stimulates alveolar bud development in mammary glands of transgenic mice. | to determine whether murine mammary growth is modulated by local insulin-like growth factor-1 (igf-1) production, expression of recombinant igf-1 was directed to the mammary glands of transgenic mice using an ovine prepro igf-1 cdna under control of the mouse mammary tumor virus-long terminal repeat (mmtv-ltr) promoter. bioactivity of recombinant igf-1 in transgenic mouse milk extracts was demonstrated by a concentration-dependent increase in [3h]thymidine incorporation in clonal bovine mammary ... | 1998 | 9741830 |
| differential gene induction by glucocorticoid and progesterone receptors. | the question of how glucocorticoid, progesterone, androgen, and mineralocorticoid receptors can generate distinct patterns of gene expression despite similar, if not identical, dna sequence recognition properties is a central question in steroid biology. this study addresses the hypothesis that glucocorticoid and progesterone receptors can differentially utilize the promoter context created by a series of receptor recognition sites. this hypothesis predicts that for different receptors an indivi ... | 1998 | 9744514 |
| ion-rna interactions in the rna pseudoknot of a ribosomal frameshifting site: molecular modeling studies. | the three-dimensional (3-d) structure of a rna pseudoknot that causes the efficient ribosomal frameshifting in the gag-pro region of mouse mammary tumor virus (mmtv) has been determined recently by nuclear magnetic resonance (nmr) studies. but since the structure refinement in the studies did not use metal ions and waters, it is not clear how metal ions participate in the stabilization of the pseudoknot, and what kind of ion-rna interactions dominate in the tertiary contacts for the rna pseudokn ... | 1998 | 9745889 |
| progesterone stimulates the activity of the promoters of peripheral myelin protein-22 and protein zero genes in schwann cells. | to understand better the mechanisms by which progesterone (prog) promotes myelination in the pns, cultured rat schwann cells were transiently transfected with reporter constructs in which luciferase expression was controlled by the promoter region of either the peripheral myelin protein-22 (pmp22) or the protein zero (p0) genes. prog stimulated the p0 promoter and promoter 1, but not promoter 2, of pmp22. the effect of prog was specific, as estradiol and testosterone only weakly activated promot ... | 1998 | 9751213 |
| transduction pathways involved in rapid hormone receptor regulation in the mammary epithelium. | previous studies have shown that the envelope protein of the mouse mammary tumor virus (mmtv) rapidly upregulates prolactin (prl) receptors by shifting them from internal pools to the cell surface and downregulates epidermal growth factor (egf) receptors by inducing their internalization and degradation. this study shows that the effect on prl receptors is mediated by the nitric oxide (no)/cgmp pathway, since it can be mimicked by an no donor or 8-bromo-cgmp and can be blocked by an no synthase ... | 1998 | 9755072 |
| possible retroviral etiology of human breast cancer. | since the discovery in the early 1980s that retroviruses are pathogenic to man, the mouse mammary tumor viruses (mmtvs) received great attention. studies of mmtvs allowed considerable insights into the mechanisms at work in breast tumorigenesis. mmtvs are essentially insertional mutagenes. numerous oncogenes have been found altered by mmtvs, either specific for mmtvs or not. however, despite considerable attempts, the involvement of mmtvs in human breast cancer remains questionable. yet a retrov ... | 1998 | 9755790 |
| p300/creb-binding protein enhances the prolactin-mediated transcriptional induction through direct interaction with the transactivation domain of stat5, but does not participate in the stat5-mediated suppression of the glucocorticoid response. | stat5 was discovered as a prl-induced member of the stat (signal transducer and activator of transcription) family. its induction by many other cytokines and interleukins suggests that stat5 plays a crucial role not only in mammary epithelial, but also in hematopoietic cells. cell type- and promoter-specific functions of stat5 are most likely modulated by the interaction with other transcription factors. we recently showed cross-talk between stat5 and the glucocorticoid receptor. the activated g ... | 1998 | 9773981 |
| active signaling by neu in transgenic mice. | transgenic mice engineered to overexpress the her-2/neu/erbb-2 protooncogene under the control of a mammary-specific promoter develop mammary tumors and are a model for human breast cancer. signal transduction by neu was examined in situ in the tumors of these transgenic mice. this was accomplished using the pn2a monoclonal antibody, which recognizes neu only in the phosphorylated, and therefore actively signaling, state. immunohistochemistry using pn2a demonstrated that neu actively signals in ... | 1998 | 9778054 |
| phorbol ester causes ligand-independent activation of the androgen receptor. | we have examined the human androgen receptor (har) for its ability to activate ar-dependent transcription of a transgene in a ligand-independent manner. the transcriptional activity was determined by analysis of chloramphenicol acetyltransferase (cat) activity in t47d cells cotransfected with a plasmid expressing the har and a natural ar-regulated promoter (the mvdp androgen-dependent enhancer) ligated to the reporter cat gene. in this study, the effects of the protein kinase c (pkc) activator 1 ... | 1998 | 9780230 |
| activation of fgf8 in s115 mouse mammary tumor cells is associated with genomic integration of mouse mammary tumor virus. | fgf8 is an embryonally expressed mitogenic fibroblast growth factor which has transforming capacity. it is expressed in s115 mouse mammary tumor cells (s115 cells) and in parental tumors of dd/sio mice as well as in some human breast and prostate cancer cell lines. in s115 cells androgens induce the expression of fgf8 which seems to be associated with the androgen-maintained malignant phenotype of the cells. s115 cells also contain and express mtv proviruses known to insertionally activate oncog ... | 1998 | 9784427 |
| expression of t:g mismatch-specific thymidine-dna glycosylase and dna methyl transferase genes during development and tumorigenesis. | in situ hybridization was used to characterize the expression pattern of the t:g mismatch-specific thymidine-dna glycosylase (tdg) gene, encoding a dna repair enzyme which corrects g:t mismatches that result from the hydrolytic deamination of 5-methyl cytosines. tdg transcripts were uniformly and ubiquitously expressed from 7.5-13.5 days post-coitum, but were then markedly enriched in specific tissues of the developing fetus. at 14.5 gestational days, tdg was strongly expressed in the developing ... | 1998 | 9794235 |
| expression of mouse mammary tumor virus-like env gene sequences in human breast cancer. | we have reported previously (wang et al, cancer res., 55: 5173-5179, 1995) the presence of a 660-bp sequence that is 90-98% homologous to the env gene of mouse mammary tumor virus in 38% of 314 unselected breast cancer samples, in some breast cancer cell lines, and in 1.8% of the 107 normal breast specimens from reduction mammoplasties. in this communication, we have investigated whether the 660-bp sequence or a smaller 256-bp sequence within the 660 bp were expressed in breast tumors, normal br ... | 1998 | 9796992 |
| regulation of mammary hormone receptor metabolism by a retroviral envelope protein. | in a previous study, the envelope protein (gp52) of the mouse mammary tumour virus (mmtv) was shown to facilitate mammary gland differentiation by increasing prolactin (prl) receptors via increased receptor synthesis and via the redistribution of existing receptors from an internal pool. in this study, receptors for other hormones known to affect mammary gland metabolism were investigated. epidermal growth factor (egf) stimulates mammary epithelial growth and inhibits differentiation; its recept ... | 1998 | 9801459 |
| differential reactivity of tcr vbeta10 alleles to a mouse mammary tumor virus superantigen. | mouse mammary tumor virus (mmtv) expresses a superantigen (sag) which plays a critical role in the viral life cycle. we have recently described the new infectious mmtv (sim) encoding a vbeta4-specific sag in mice with a tcr-vbeta(b) haplotype. we have now compared the sag activity of this virus in balb/c mice harboring the tcr-vbeta(a), tcr-vbeta(b) or tcr-vbeta(c) haplotypes which differ by a central deletion in the tcr-vbeta(a) and tcr-vbeta(c) locus and by mutations in some of the remaining v ... | 1998 | 9808176 |
| mouse mammary tumor virus sequences responsible for activating cellular oncogenes. | integration of mouse mammary tumor virus (mmtv) near the int genes results in the inappropriate expression of these proto-oncogenes and initiates events that lead to the formation of mammary adenocarcinomas. in most cases, the mmtv provirus integrates in a transcriptional orientation opposite that of the int genes. we have used a novel, vector-based system designed to recapitulate the integration of mmtv upstream of the int-2 promoter. compared to a cellular promoter or another retroviral promot ... | 1998 | 9811675 |
| the regional integration of retroviral sequences into the mosaic genomes of mammals. | we have reviewed here three sets of data concerning the integration of retroviral sequences in the mammalian genome: (i) our experimental localization of a number of proviruses integrated in isochores characterized by different gc levels; (ii) results from other laboratories on the localization of retroviral sequences in open chromatin regions and/or next to cpg islands; and (iii) our compositional analysis of genes located in the neighborhood of integrated retroviral sequences. the three sets o ... | 1998 | 9813219 |