| low incidence of tumourigenicity in agarose colonies from spontaneous murine mammary tumours. | in these experiments individual colonies growing in agarose seeded with monocellular suspensions from freshly disaggregated naturally-occurring mouse mammary tumours, induced by the murine mammary tumour virus (mmtv), were reimplanted into mammary fat pads of virus-free mice. it was found that only a small proportion of these colonies generated tumours and that the implantation of multiple colonies in each site did not result in disproportionate, synergistic, increase in tumour takes. it was als ... | 1989 | 2612768 |
| high level expression in escherichia coli of the dna-binding domain of the glucocorticoid receptor in a functional form utilizing domain-specific cleavage of a fusion protein. | a fragment comprising the dna-binding domain of the human glucocorticoid receptor has been expressed in a functional form in escherichia coli as a fusion protein with protein a from staphylococcus aureus. the dna-binding domain was purified to apparent homogeneity by affinity chromatography on igg-sepharose and dna-cellulose, a purification scheme which does not involve denaturation of the protein at any step. the dna-binding domain was separated from the protein a part of the fusion protein by ... | 1989 | 2642905 |
| inducible overexpression and secretion of int-1 protein. | the int-1 proto-oncogene is a target for insertional activation of transcription by mouse mammary tumor virus in many murine mammary tumors. whereas no expression of int-1 is seen in normal mammary tissue, int-1 rna can be detected in normal mice in the neural tubes of midgestation embryos and in postmeiotic spermatocytes from adult testes. i report here the results of a study in which several different antibodies against synthetic peptides were produced and used to characterize the processing a ... | 1989 | 2677670 |
| a homologue of retroviral pseudoproteases in the parapoxvirus, orf virus. | the nucleotide sequence of a near-terminal region of orf virus dna was determined. examination of the sequence revealed an open reading frame encoding a peptide with significant amino acid homology to the pseudoprotease domains recently identified in a number of retroviruses including mouse mammary tumor virus, simian mason-pfizer virus, maedi-visna virus, and equine infectious anaemia virus. the orf virus pseudoprotease shares up to 28% amino acid homology with retroviral pseudoproteases and ap ... | 1989 | 2678731 |
| mutations in human breast cancer: an overview. | studies of mammary tumorigenesis in mice infected with the mouse mammary tumor virus and in certain strains of transgenic mice with an activated oncogene have provided strong evidence that multiple mutations contribute to the initiation and progression of malignancies in the breast. the increasing availability of recombinant dna probes that detect various proto-oncogenes, growth factor genes, and growth factor receptor genes, as well as restriction fragment length polymorphisms in the human popu ... | 1989 | 2685334 |
| the contribution of the n- and c-terminal regions of steroid receptors to activation of transcription is both receptor and cell-specific. | normalized dose response-curves for transcriptional activation of reporter genes were obtained by co-transfecting them with increasing amounts of wild-type (wt) progesterone (pr), glucocorticoid (gr) and oestrogen (er) expression vectors. marked differences in both shape and magnitude of the stimulation were observed depending on whether hela or cv1 cells were transfected. in hela cells the transcriptional stimulation from a reporter gene containing the hormone responsive element (re) present in ... | 1989 | 2717402 |
| characterization of human glucocorticoid receptor complexes formed with dna fragments containing or lacking glucocorticoid response elements. | sucrose density gradient shift assays were used to study the interactions of human glucocorticoid receptors (gr) with small dna fragments either containing or lacking glucocorticoid response element (gre) dna consensus sequences. when crude cytoplasmic extracts containing [3h]triamcinolone acetonide [( 3h]ta) labeled gr were incubated with unlabeled dna under conditions of dna excess, a gre-containing dna fragment obtained from the 5' long terminal repeat of mouse mammary tumor virus (mmtv ltr) ... | 1989 | 2719940 |
| thymic atrophy characteristic in transgenic mice that harbor px genes of human t-cell leukemia virus type i. | the human t-cell leukemia viruses (htlv) are associated with t-cell malignancies in humans. the malignant transformation occurs after a long latency in some carriers, and its mechanism appears to be distinct from that of other classes of retroviruses which induce transformation through viral or cellular oncogenes. a widely postulated explanation is that the products of novel px genes transactivate endogenous cellular genes which lead to tumor development in t cells. to directly examine the patho ... | 1989 | 2724422 |
| reversible cellular senescence: implications for immortalization of normal human diploid fibroblasts. | imr-90 normal human diploid fibroblasts, transfected with a steroid inducible mouse mammary tumor virus-driven simian virus 40 t antigen, were carried through crisis to yield an immortal cell line. growth was dependent on the presence of the inducer (dexamethasone) during both the extended precrisis life span of the cells and after immortalization. after dexamethasone removal, immortal cells divided once or twice and then accumulated in g1. these results are best explained by a two-stage model f ... | 1989 | 2779554 |
| improved anti-tumor reactivity with monoclonal anti-idiotypic antibody conjugated to syngeneic mouse red blood cells. | an anti-idiotypic (anti-id) antibody (ab), by resembling an epitope on an antigenic molecule may serve as a surrogate antigen and induce specific immune reactivity to the natural antigen. anti-id ab are often conjugated to a foreign protein, such as keyhole limpet hemocyanin (klh) to elicit a stronger response. however, klh, a potent antigen itself, may provoke unnecessary and undesirable immune reactivity. in this study, syngeneic mouse red blood cells (rbc) were tested as carriers for anti-id ... | 1989 | 2794517 |
| an expression vector for high-level protein synthesis in vero cells. | we have constructed two new multi-purpose cloning vectors, pni1 and pni2, that carry the escherichia coli gene ecogpt encoding the enzyme xanthine-guanine phosphoribosyl transferase as a dominant selective marker. the ecogpt gene is under the control of either the long-terminal-repeat promoter of mouse mammary tumor virus, pni1, or the simian virus 40 early promoter, pni2. another feature of the vectors is a polylinker preceded by the human metallothionein iia promoter. we have used pni2 for the ... | 1989 | 2806920 |
| different adenovirus e1a-controlled properties of transformed cells require different levels of e1a expression. | we have transformed primary baby rat kidney cells with a plasmid containing the adenovirus(ad)12e1 region in which the e1a promoter was replaced by the dexamethasone inducible mouse mammary tumor virus promoter. in the uninduced state the level of e1a expression is less than 10% of that in the induced state. we have investigated the effects of decreasing the levels of e1a on a number of e1a-mediated processes. first, expression of the e1b region is reduced several-fold upon reducing e1a expressi ... | 1987 | 2820846 |
| isolation and characterization of minichromosome particles that contain a glucocorticoid-modulated promoter. | a procedure for the enrichment of minichromosomes, composed of bovine papilloma virus and the long terminal repeat element of the mouse mammary tumor virus (mtv), from isolated nuclei is described. up to 60% of the minichromosomes were extracted as nucleoprotein particles. these particles sediment in sucrose gradients as 160s complexes. hormone-labeled glucocorticoid receptor co-purifies with these complexes in a specific fashion. between four and six molecules of receptor are bound per minichro ... | 1987 | 2821487 |
| transcriptional repression of a hormone-responsive promoter. | the activity of the mouse mammary tumor virus promoter was assessed in various sequence contexts with a transient transfection assay in which promoter activity was determined by way of expression of a linked gene encoding chloramphenicol acetyltransferase, as well as by direct analysis of rna transcripts. the results indicate that the proviral long terminal repeat contains a negative transcriptional control element in addition to the glucocorticoid-responsive transcriptional enhancer that has be ... | 1987 | 2821488 |
| characterization of the dim series of balb/c preneoplasms for mouse mammary tumor virus-mediated oncogenesis. | the dim series of preneoplasms, developed from the balb/c mammary cell line comma-d, and dim-derived tumors were examined for evidence of mouse mammary tumor virus (mmtv) involvement in the tumorigenic process. dim tissues were shown to be free of exogenous mmtv inasmuch as southern blot analysis of dnas extracted from dim preneoplasms and tumors showed the lack of a psti-generated 4.2-kilobase mmtv-gag-pol band. to examine the possibility of endogenous mmtv action via enhancer insertion, dnas f ... | 1987 | 2822232 |
| sequence-specific positioning of nucleosomes over the steroid-inducible mmtv promoter. | we have investigated chromatin organization over the mmtv ltr, a promoter regulated by steroid hormones. the studies were performed on cell lines containing bpv-based episomal constructs. nucleosome positioning was determined by localization of sites sensitive to the enzyme micrococcal nuclease, or to the chemical mpe-fe(ii). experiments with both reagents indicate that nucleosomes are specifically positioned in mmtv ltr chromatin. in the absence of hormone a regular cutting pattern is obtained, ... | 1987 | 2822386 |
| molecular aspects of mouse mammary tumor virus biology. | | 1987 | 2822592 |
| characterization of mouse mammary tumor virus gag-pro gene products and the ribosomal frameshift site by protein sequencing. | the synthesis of retroviral polyproteins that are the translational products of the genome-size mrna is initiated in the upstream gag gene. the synthesis of the products of the protease gene (pro) and polymerase gene (pol) is regulated by translational suppression (in-frame read-through or frameshift) of termination codons as a strategy developed for controlling the level of replicative enzymes required only in catalytic amounts. in mouse mammary tumor virus (mmtv), three overlapping reading fra ... | 1987 | 2823251 |
| [heterotopic production and tumorigenesis of mouse mammary tumor virus (mmtv)--can mmtv be a causative agent of lymphoid leukemias?]. | | 1987 | 2823474 |
| current perspectives in the biology of mouse mammary tumour virus. | | 1987 | 2823501 |
| induction of transcription by steroid hormones. | | 1987 | 2823900 |
| progression to steroid insensitivity can occur irrespective of the presence of functional steroid receptors. | a major problem in treatment of cancers arising in steroid-sensitive cells is their inevitable progression to a steroid-insensitive state; current therapies are based on the assumption that hormone insensitivity is associated with loss of receptor. we demonstrate for the first time that breast tumor cells can progress to steroid insensitivity in spite of functional steroid receptors. transfection of the steroid-inducible ltr-c3 gene into unresponsive s115 mouse mammary tumor cells results in ful ... | 1987 | 2824060 |
| chromatographic purification and immunological analysis of viral polypeptides of mouse mammary tumor virus. | the seven mouse mammary tumor virus (mmtv) structural polypeptides (gp52, gp36, p28, p23, p14, p12, and p10) were purified to apparent homogeneity. an improved and reproducible chromatographic method was used to obtain high yields of viral proteins from the same batch of isopycnically purified mmtv. the viral structural proteins were first extracted repeatedly with a high salt and high ph buffer in the presence of 1% triton x-100. loss of the minor viral proteins during column purification was m ... | 1987 | 2824547 |
| analysis of the idiotypic network in tumor immunity. | herein we have analyzed the expression of idiotopes associated with a monoclonal anti-tumor-associated antigen (taa) antibody in dba/2 mice which have progressively growing tumors or resist tumor growth. a panel of eight monoclonal antiidiotypic antibodies raised against a monoclonal antibody which reacts with a mouse mammary tumor virus cross-reactive qp52 envelope protein (taa) of the l1210/gzl lymphoma was used to measure the expression of idiotopes in sera from different treatment groups. si ... | 1987 | 2824616 |
| [endogenous mmtv in the normal mammary gland and in dimethylanthracene-induced mammary cancer in balb/c mice]. | immunization of dmba-treated mice by the glycoprotein fraction from mammary glands of mice balb/c did not decrease the frequencies of induction of mammary tumors. this is in contrast to the results obtained during immunization by the formaldehyde treated preparation of mouse mammary tumor virus (mmtv). ecori and hindiii cleaved dna from the dmba-induced mammary tumors did not contain the additional virus specific fragments. in mammary tumors the expression of p27 mmtv was registered in contrast ... | 1987 | 2825005 |
| a novel human nonviral retroposon derived from an endogenous retrovirus. | in a human genome, we found dispersed repetitive sequences homologous to part of a human endogenous retrovirus termed herv-k which resembled mouse mammary tumor virus. for elucidation of their structure and organization, we cloned some of these sequences from a human gene library. the sequence common to the cloned dna was ca. 630 base-pairs (bp) in length with an a-rich tail at the 3' end and was found to be a sine (short interspersed repeated sequence) type nonviral retroposon. in this retropos ... | 1987 | 2825118 |
| characterization of early molecular biological events associated with thymic lymphoma induction following infection with a thymotropic type-b retrovirus. | a highly leukemogenic virus (dmba-lv) induces thymic lymphomas with a very short (40 days) latent period. all induced tumors contain low numbers of new integrated dmba-lv type-b proviruses and tumorigenicity of dmba-lv is completely abolished by a monoclonal antibody directed toward an envelope determinant present on a type-b mammary tumor-inducing viral isolate. while the dmba-lv type-b genome is very highly related to mammary tumor-inducing isolates it does have unique gp52 and p28 proteins as ... | 1987 | 2825409 |
| morphological characterization of a granulocytosis/hypercalcemia-inducing murine mammary carcinoma cell line. | a newly established cell line of a granulocytosis/hypercalcemia-inducing murine mammary carcinoma (ce mammary carcinoma) grown in serum-free culture medium secretes factors that stimulate proliferation of granulocytes and embryonal bone cells. these cultured cells retain the ability to produce granulocytosis and hypercalcemia when they are transplanted back into mice. in culture these cells form clusters of organized cells. studies by scanning, transmission, and freeze-fracture electron microsco ... | 1987 | 2825563 |
| a subset of normal human b lymphocytes expresses an antigen cross-reactive with gp52 of murine mammary tumor virus. | three monoclonal antibodies (mabs), ve7, vig3, and ixf9, that detect the 52-kd glycoprotein (gp52) of murine mammary tumor virus (mmtv) were tested for reactivity on normal human tonsillar lymphoid cells in an indirect immunofluorescence assay. two of the mabs, ve7 and vig3, reacted with subpopulations of b cells, whereas the third mab, ixf9, showed only very low-level reactivity with human lymphoid cells. ve7 and vig3 also reacted with small populations of peripheral blood lymphocytes, and all ... | 1987 | 2825999 |
| prognostic factors in breast cancer--a pathological and immunological study of patients with stage 1 breast cancer. | in order to analyze which features determine a poorer prognosis we undertook a study of 91 consecutive patients with pathological stage i breast cancer operated on at beth israel medical center (1968-71). tumor tissue slides were reviewed and features such as: tumor size, histologic type, nuclear grade, lymphocytic and perivenular lymphocytic infiltration, as well as sinus histiocytosis in the lymph nodes removed. records were reviewed and classified according to age and ethnic background. survi ... | 1987 | 2826257 |
| interaction of different steroid hormones during progression of tumour cells to steroid autonomy. | progression to steroid insensitivity poses a major problem in therapy of breast cancer, but studies of the origin of steroid-insensitive cells have been few and have concentrated in any one system on the loss of response to only one steroid. since both normal and tumour mammary cells have complex endocrine requirements, we wondered how different steroids might interact during loss of steroid sensitivity. cloned cells from the androgen-responsive shionogi 115 mouse mammary carcinoma respond in vi ... | 1987 | 2826338 |
| mouse mammary tumor proviruses from a t-cell lymphoma are associated with the retroposon l1md. | four charon 4a clones containing mouse mammary tumor virus (mmtv) proviruses and their cellular flanking sequences were obtained from partial ecori libraries of a c57bl/6 t-cell lymphoma with both endogenous and newly acquired mmtv proviruses. the cellular flanking sequences of three of four mmtv proviruses contained dna homologous to the 3' end of the long interspersed retroposon l1md. two of the three proviruses were newly acquired in the lymphoma dna, and these mmtv proviruses appeared to be ... | 1988 | 2826809 |
| hormonal regulation of mouse mammary tumor growth. | in view of reports that human breast cancer cells secrete growth factors that can replace estradiol in sustaining tumor growth [1], we have investigated whether hormone independent (hi) gr mouse mammary tumors can sustain growth of estrogen-depleted hormone dependent (hd) tumors. hd gr mammary tumor tsl 106 was grafted subcutaneously in the right flank of estrone plus progesterone treated castrated (020 x gr)f1 mice. after 2 weeks the estrone treatment was stopped and the mice received 50, 100 o ... | 1987 | 2826887 |
| gene regulation by steroid hormones. | the location, orientation, and structure of the hormone regulatory elements (hre) in nine hormonally modulated genes is described. based on analysis of the contact points between the glucocorticoid receptor (gr) and the dna double helix within the hres, a model for the interaction is proposed in which a dimer of the receptor in head-to-head orientation binds to the inverted symmetry element of the hre. the relationship between the regulatory elements for glucocorticoids and progesterone in the l ... | 1987 | 2826895 |
| multiple regulatory domains in the mouse mammary tumor virus long terminal repeat revealed by analysis of fusion genes in transgenic mice. | transcription initiated within the mouse mammary tumor virus (mtv) long terminal repeat (ltr) is regulated by glucocorticoids, androgens, and estrogen. however, expression of the virus in vivo and transcription of mtv ltr fusion genes in transgenic mice are not readily interpretable solely in terms of the influence of these hormones. to investigate whether there is a regulatory role for sequences within the ltr but outside the region known to be responsible for glucocorticoid induction, we have ... | 1988 | 2827009 |
| identification of protein products encoded by the proto-oncogene int-1. | the proto-oncogene int-1 is activated by adjacent insertions of proviral dna in mouse mammary tumor virus-induced tumors and has transforming activity in certain mammary epithelial cell lines. the gene is normally expressed in the central nervous system of mid-gestational embryos and in the adult testis. we raised antibodies against synthetic int-1 peptides and used these to identify protein products of the gene in cells transfected or infected with retroviral vectors expressing int-1. four prot ... | 1987 | 2828922 |
| binding of multiple factors to the mmtv promoter in crude and fractionated nuclear extracts. | hormone activation of mmtv transcription results in the establishment of a tightly bound transcription factor complex at the promoter (cordingley et al., cell 48, 261-270, 1987). we have characterized two fractionable binding activities which participate in this complex. one factor, previously identified as the mouse homologue of nf-1 (or ctf), protects sequences -82 to -56 from exonuclease iii digestion in vitro. sequences protected by a second factor (-42 to -4) span the tata box of the promot ... | 1988 | 2829133 |
| glucocorticoid-dependent complementation of a hepatoma cell variant defective in viral glycoprotein sorting. | we have utilized the rat hepatoma (htc) cell sorting variant cr4 to examine the glucocorticoid-regulated pathways that localize mouse mammary tumor virus glycoproteins to the cell surface. the defective sorting of cell surface mouse mammary tumor virus glycoproteins in cr4 cells was complemented after fusion with either normal rat hepatocytes or uninfected htc cells. indirect immunofluorescence of transient heterokaryons revealed that the regulated localization of mouse mammary tumor virus glyco ... | 1988 | 2829203 |
| gal4 activates gene expression in mammalian cells. | gal4, a protein that activates transcription in yeast, is shown to activate the mouse mammary tumor virus promoter in mammalian cells. activation depends upon a gal4-binding sequence inserted upstream of the gene. deletion mutants of gal4 bearing one or both of the "activating regions" required for activation in yeast also activate transcription in mammalian cells. a derivative of gal4 that binds to dna but cannot activate transcription in yeast also fails to activate transcription in mammalian ... | 1988 | 2830021 |
| immunoelectron microscopic localization of mammary tumor virus (mtv) antigens in normal and cancerous mammary glands of mice. | peroxidase-labeled fab' fragments of rabbit antisera against gp52 (major envelope protein) and a-particles of mammary tumor virus (mtv) were prepared and used for investigation by immunoelectron microscopy of the replication cycle of mtv-specific envelope and core antigens in normal and malignant mammary gland cells of female mice. the specificity of the antisera was proven by absorption tests and lack of reactivity to mtv-free mammary tissues. periodate-lysine-paraformaldehyde (plp) fixation su ... | 1987 | 2830473 |
| glucocorticoid-resistant lymphoma cell variants that contain functional glucocorticoid receptors. | a mouse t-lymphosarcoma cell line stably infected with mouse mammary tumor virus (mmtv) was used as the parent line for a genetic analysis of two glucocorticoid hormone responses, hormone-induced cytolysis and stimulation of viral gene expression. variants were selected for survival and elevated expression of mmtv proteins in the presence of the steroid. the mmtv marker provided a sensitive test for glucocorticoid receptor (gr) function in the hormone-resistant variants. this strategy resulted i ... | 1987 | 2830485 |
| genetic evidence that the steroid-regulated trafficking of cell surface glycoproteins in rat hepatoma cells is mediated by glucocorticoid-inducible cellular components. | the biological control of posttranslational maturation and compartmentalization reactions that operate upon proteins during transport to their final cellular destinations is crucial for normal cellular function. using the expression of mouse mammary tumor virus (mmtv) glycoproteins as sensitive probes in the viral-infected rat hepatoma cell line m1.54, we have discovered and documented a novel glucocorticoid-regulated trafficking pathway that controls the cell surface localization of mmtv glycop ... | 1987 | 2831239 |
| identification of androgen response elements in mouse mammary tumour virus and the rat prostate c3 gene. | the effect of steroid hormones on mouse mammary tumour virus (mmtv) promoter activity has been analysed in the breast cancer cell lines zr-75-1 and t-47d 11. both androgens and progestins were stimulatory in both cell lines, whereas glucocorticoids were stimulatory in only zr-75 cells. a glucocorticoid response was restored to t-47d cells by the transient expression of a glucocorticoid receptor expression vector, suggesting that endogenous receptors were limiting. the effect of androgen was medi ... | 1987 | 2831240 |
| expression of human sequences related to those of mouse mammary tumor virus. | sequences related to those of the mouse mammary tumor virus (mumtv) genome have been cloned from human dna by screening a library prepared from the dna of a human breast cancer cell line with mumtv gag-pol dna. nine distinct groups of (mumtv-related) sequences were identified among 100 lambda recombinants by cross-hybridization experiments with subcloned fragments containing gag-pol-related dna. the largest group, of 64 recombinants, contains the mumtv-related sequences cloned by others. the oth ... | 1988 | 2831381 |
| structural and functional analysis of long terminal repeats of suncus murinus mammary tumor virus. | a 2.7-kilobase (kb) cdna sequence complementary to suncus murinus mammary tumor virus (sm-mtv) genomic rna [corrected] was prepared using purified virions produced by the sm-mt cell line, which had been established from a spontaneous mammary tumor of s. murinus. it was found, by using this cdna in southern hybridization experiments, that sm-mtv was endogenous to this animal and that some 50 copies of endogenous provirus were present per haploid cellular genome. in addition, a proviral sm-mtv dna ... | 1988 | 2831384 |
| phorbol diester-inducible, cyclosporine-suppressible transcription from a novel promoter within the mouse mammary tumor virus env gene. | the mouse t-cell lymphoma cell line el4.e1 constitutively synthesizes mouse mammary tumor virus (mmtv) transcripts encoding either the entire proviral genome or segments of it. in addition to these conventional mrnas, however, an mrna of about 1 kilobase accumulates after induction of these cells with phorbol myristate acetate (pma). the accumulation of this transcript is strongly inhibited by the immunosuppressive agent cyclosporin a. its pattern of induction by pma and suppression by cyclospor ... | 1988 | 2831399 |
| cooperativity of the glucocorticoid receptor and the caccc-box binding factor. | glucocorticoid receptor binding sites (gre) are often tightly clustered with other transcription factor binding sequences. examples of this occur upstream of the genes for chicken lysozyme and human metallothionein iia (ref. 3), in several retroviral ltrs and upstream of the rat tryptophan oxygenase (to) gene. in the to gene, sequences immediately upstream of a glucocorticoid receptor binding site are required for steroid induction and contain a caccc-box identical to that found in the beta glob ... | 1988 | 2831456 |
| different int-1 region dna rearrangements within different zones of a single mouse mammary tumor. | fragments were taken from separate parts of hormone-dependent (hd) primary gr mouse mammary tumors and serially transplanted in estrone plus progesterone treated or hormonally untreated castrated mice. the transplants were examined with respect to int-1 dna rearrangement, proviral integrations of the murine mammary tumor virus (mmtv), and estrogen and progesterone receptor content. one of the fragments (b) taken from the primary tumor of line tsi 96 produced transplants that showed int-1 rearran ... | 1988 | 2831652 |
| human monoclonal antibodies derived from pleural effusion lymphocytes of a patient with breast carcinoma react with human breast cancer-associated antigens and mouse mammary tumor virus polypeptides. | four human hybridoma cell lines (peb1-4) were established from a fusion of pleural effusion lymphocytes isolated from a breast cancer patient with metastatic disease, 6 years postmastectomy. the hybridomas secreted igg-k (3 micrograms/ml/10(6) cells). these monoclonal antibodies (peb1-4) reacted to different degrees with mouse mammary tumor virus (mmtv) and t47d particles (humtv). immunological cross-reaction was also detected with antigens isolated from body fluids of breast cancer patients (bf ... | 1987 | 2832225 |
| temperature-sensitive transport of glycoproteins to the surface of a variant mouse lymphoma cell line. | the expression of mouse mammary tumor virus (mmtv) glycoproteins on the surface of stably infected mouse lymphoma cell line w7mg1 is dramatically increased by glucocorticoid hormones. a variant cell line, w7m.ts1, was selected from w7mg1 for its lack of expression of mmtv glycoproteins on the cell surface in response to treatment with glucocorticoid. hormonal stimulation of mmtv rna levels and hormone-induced cytolysis occurred normally in the variant cells. furthermore, the rates of production ... | 1988 | 2832739 |
| [presence of antibodies specifically reacting with structural proteins of the mammary cancer virus among antibodies found in circulating immune complexes in patients with breast cancer]. | circulating immune complexes were precipitated from breast cancer patients' sera using 2.5% polyethylene glycol. cic isolated from 70 ml of sera from 15 patients were dissociated and immunoglobulin-containing fraction was prepared by chromatography on sephadex g-200 column. the fraction contained igg specific for mumtv structural proteins, as revealed by elisa. cic preparations from 22 sera of breast cancer patients were digested with pepsin; fab' fragment preparations were also analysed by elis ... | 1988 | 2833956 |
| differences in progression of balb/cfriii and balb/cfc3h mammary hyperplastic alveolar nodules transplanted into the gland-free fat pads of balb/c mice. | in balb/cfc3h and balb/cfriii virgin female mice, i.e., balb/c mice carrying milk-transmitted c3h and those carrying riii murine mammary tumor virus infection, respectively, mammary noduligenesis and tumorigenesis are remarkably different. focal hyperplastic alveolar changes or hyperplastic alveolar nodules were removed from balb/cfriii or balb/cfc3h breeding female donors and transplanted into the gland-free mammary fat pads of syngeneic balb/c virgin female recipients with or without hormonal ... | 1988 | 2835155 |
| differential gene activation by glucocorticoids and progestins through the hormone regulatory element of mouse mammary tumor virus. | the hormone regulatory element (hre) of mouse mammary tumor virus can mediate activation of an adjacent promoter by glucocorticoids and progestins. a detailed comparison of the dna binding of receptors for both hormones using dnaase i footprinting and methylation protection detects clear differences in their interactions with the hre region between positions -130 and -100. binding studies and gene transfer experiments with a variety of mutants covering the entire hre demonstrate differences in t ... | 1988 | 2835167 |
| the n-terminal region of the chicken progesterone receptor specifies target gene activation. | steroid hormone receptors belong to a family of nuclear receptors that trigger transcriptional activation of target genes by specific binding to dna recognition sequences, usually located in the 5'-flanking region of the target gene. nuclear receptors appear to be segmented proteins and extensive structure-function analyses have attempted to elucidate the functional significance of individual segments. two of these regions have been defined as the domains responsible for recognition of responsiv ... | 1988 | 2835683 |
| amplification of the int-2 gene in primary human breast tumors. | proviral activation of the int-2 gene is a frequent occurrence in mammary carcinomas induced by mouse mammary tumor virus (mmtv). here, we have examined the human homolog of int-2 in 110 primary breast cancer dnas. the locus was amplified 2- to 15-fold in 18 of the tumor dna samples. amplification of int-2 has a highly significant association (p less than 2 x 10(-6] with tumors from patients who subsequently developed a local recurrence of the disease or a distal metastasis. | 1988 | 2835739 |
| glucocorticoid-regulated localization of cell surface glycoproteins in rat hepatoma cells is mediated within the golgi complex. | glucocorticoid hormones regulate the post-translational maturation and sorting of cell surface and extracellular mouse mammary tumor virus (mmtv) glycoproteins in m1.54 cells, a stably infected rat hepatoma cell line. exposure to monensin significantly reduced the proteolytic maturation and externalization of viral glycoproteins resulting in a stable cellular accumulation of a single 70,000-mr glycosylated polyprotein (designated gp70). cell surface- and intracellular-specific immunoprecipitatio ... | 1988 | 2836430 |
| a transcriptionally defective long terminal repeat within an endogenous copy of mouse mammary tumor virus proviral dna. | mouse mammary tumor virus proviral dna is endogenous to most inbred strains of mice but in many strains is not transcriptionally active. this inactivity may be due to defects in the proviruses themselves or to position effects mediated by dna sequences flanking the proviral units. the transcriptional competence of long terminal repeats (ltrs) derived from endogenous proviral dna at genetic loci mtv-8, mtv-9, and mtv-17 of the c57bl/6 mouse strain was examined with a transient transfection assay ... | 1988 | 2836622 |
| mouse mammary tumor virus (mmtv) particles in extraorbital lacrymal and urethral glands of endogenous mmtv-carrying mice. | expression of mouse mammary tumor virus (mmtv) antigens was observed in a wide variety of exocrine glands in adult mice by an immunoperoxidase method using rabbit antisera against gp52 and p27 of mmtv. both exogenous and endogenous mmtv-carrying shn, grs/a, c3h and ddd-mtv-2 mice expressed both antigens in the mammary, extraorbital lacrymal, urethral, parotid and submandibular glands of both sexes and prostate, seminal vesicle and epididymis but not in the harder's, zymbal's sublingual and uteri ... | 1987 | 2836642 |
| [specificity of antibodies against structural proteins of the mouse mammary cancer virus in healthy women and in mastopathy]. | the immunoenzyme technique was used to identify sera reacting with mouse mammary tumor virus (mmtv) proteins in patients with mastopathy and healthy subjects. their specificity to certain viral proteins was established by immunoblotting. serum samples obtained from 14 subjects reacted mainly with p27 mmtv, while those taken from another two subjects--mainly with gp52 virus. humoral antibodies against p27 mmtv were found in 3.3% of the entire study group whereas anti-gp52 antibodies--in 0.5%. | 1988 | 2837004 |
| a role for divalent cations in specifying the start site for transcription from chromatin templates in vitro. | an assay that employs nucleoside 5'-o-(2-thiotriphosphates) was used to detect initiation of mouse mammary tumor virus (mmtv) rna chains in preparations of isolated nuclei from cultured rat hepatoma cells containing stably integrated proviruses. rna chains initiated with adenosine 5'-o-(2-thiotriphosphate), guanosine 5'-o-(2-thiotriphosphate), or uridine 5'-o-(2-thiotriphosphate) were separated from the remaining rna by mercury-sepharose column chromatography and analyzed for correctly initiated ... | 1988 | 2837493 |
| mineralocorticoid regulation of transcription of transfected mouse mammary tumor virus dna in cultured kidney cells. | renal cells contain two corticosteroid-binding entities defined on the basis of hormone-binding selectivity as type i (mineralocorticoid) and type ii (glucocorticoid). the mineralocorticoid, aldosterone can bind to both type i and type ii receptors. this poses problems in defining the characteristics of a true mineralocorticoid regulated expression of specific genes. we have used chimaeric constructs bearing the mouse mammary tumor virus (mmtv) promoter to study aldosterone action in the feline ... | 1988 | 2838493 |
| analysis of regulatory sequences in androgen-responsive genes. | we have analysed the effect of androgens on the activity of promoters from mmtv, and the rat prostate c3(1) and mouse secretory protease inhibitor genes. mmtv promoter activity was stimulated by testosterone as well as progesterone and dexamethasone but not by oestradiol. deletion analysis indicated that the three steroids acted through dna sequences between nucleotides -201 and -69 upstream of the mmtv cap site. in contrast, the promoters for the c3(1) gene and the protease inhibitor gene were ... | 1988 | 2838701 |
| characterization of response elements for androgens, glucocorticoids and progestins in mouse mammary tumour virus. | we have characterized steroid response elements in mouse mammary tumour virus (mmtv) by transient transfection. four partial inverted repeats of the sequence tgttct function as response elements for androgen, as well as for glucocorticoid and progestins, although the relative hormone inductions mediated by each oligonucleotide were different. mutational analysis of the left half of the palindrome showed that a perfect dyad symmetry is not required for optimum activity as a steroid response eleme ... | 1988 | 2838812 |
| alterations in the u3 region of the long terminal repeat of an infectious thymotropic type b retrovirus. | we isolated and characterized a type b thymotropic retrovirus (dmba-lv) which is highly related to mouse mammary tumor virus (mmtv) isolates and which induces t-cell thymomas with a high incidence and a very short latent period. regions of nonhomology between the dmba-lv genome and the mmtv genome were identified by heteroduplex mapping and nucleotide sequence studies. in the electron microscope heteroduplex mapping studies the ecori-generated 5' and 3' fragments of the dmba-lv genome were compa ... | 1988 | 2839715 |
| endogenous mouse mammary tumor virus is expressed in several organs in addition to the lactating mammary gland. | we studied the transcription of endogenous mouse mammary tumor virus (mmtv) in transgenic and normal strains of mice of different genetic backgrounds. although the lactating mammary gland in all strains showed the highest level of mmtv expression, detectable levels of viral rna were also found in the lungs, kidneys, salivary glands, seminal vesicles and/or prostate gland, testes, and lymphoid tissue in mice which contain different endogenous proviruses. transcription in transgenic mice containin ... | 1988 | 2839721 |
| the mmtv ltr promoter is induced by progesterone and dihydrotestosterone but not by estrogen. | induction of the mouse mammary tumor virus (mmtv) promoter by steroid hormones was examined in chick oviduct primary cell cultures transfected with mmtv-chloramphenicol acetyl transferase fusion constructs. our results demonstrate that in this system glucocorticoids, progesterone and dihydrotestosterone are all able to stimulate mmtv transcription; induction by progesterone and dihydrotestosterone is not mediated by glucocorticoid receptors, since the specific glucocorticoid antagonist ru486 did ... | 1988 | 2840570 |
| possible involvement of two signaling pathways in induction of neuron-associated properties by v-ha-ras gene in pc12 cells. | harvey sarcoma virus induces a number of neuron-associated properties in a nerve growth factor-responsive cell line, pc12 (noda, m., ko, m., ogura, a., liu, d., amano, t., takano, t., and ikawa, y. (1985) nature 318, 73-75). we investigated the mechanism of this phenomenon using pc12 sublines cotransfected with a plasmid containing v-ha-ras gene under control of a hormone-responsive enhancer/promoter element of the mouse mammary tumor virus long terminal repeat (pm14-1) and a plasmid encoding g4 ... | 1988 | 2841343 |
| dna sequences outside the receptor-binding sites differently modulate the responsiveness of the mouse mammary tumour virus promoter to various steroid hormones. | glucocorticoids, progestins and androgens all induce the transcription of the mouse mammary tumour virus (mmtv) dna upon binding of their respective receptors to the hormone response element (hre). this element is located between -202 and -59 5' upstream of the start of transcription on the mmtv long terminal repeat (ltr) region. the hre contains four repeats of the hexanucleotide 5'-tgttct-3' to which the steroid hormone receptors are thought to bind. to investigate the contribution of the indi ... | 1988 | 2842149 |
| simultaneous observation of the antigen localization in an identical semithin secretion with both light and transmission electron microscopes. | | 1988 | 2842426 |
| effects of repeated exposure to cyclophosphamide on drug resistance and biological properties of a newly autonomy-acquired mouse mammary tumor (t4-oi320). | t4-oi320 tumors, the autonomous but estrogen receptor (er-)-positive subline recently established from the pregnancy-dependent tpdmt-4 mouse mammary tumor, were characterized by moderate sensitivity to 1 mg cyclophosphamide (cy) and high sensitivity to 20 micrograms mitomycin c (mmc) and 1.5 mg 5-fluorouracil (5fu) twice weekly, the modal chromosome number of 40, the mean er level of 20.8 fmol/mg protein, and a population of cells with one exogenous mouse mammary tumor virus (mmtv) genome. seria ... | 1988 | 2842525 |
| intracellular receptor concentration limits glucocorticoid-dependent enhancer activity. | the glucocorticoid receptor protein, in association with cognate hormonal ligands, binds with high affinity to specific dna sequences termed glucocorticoid response elements (gres) which can function as hormone-dependent transcriptional enhancers; thus, the receptor is a regulable enhancer-activating protein. we have constructed cell lines expressing different levels of glucocorticoid receptor, and demonstrate that the extent of a structural alteration in the chromatin at a characterized gre, as ... | 1987 | 2842660 |
| c-h-ras-1 expression in 7,12-dimethyl benzanthracene-induced balb/c mouse mammary hyperplasias and their tumors. | dimethylbenzanthracene (dmba)-induced mouse mammary tumors characteristically contain an activated c-h-ras-1 gene with an a----t transversion in the 61st codon which is expressed as a rapidly migrating p21 c-h-ras. the role of the activated c-h-ras-1 locus in the initiation of mammary neoplasia was analysed by studying seven transplantable, dmba-induced balb/c premalignant mammary hyperplasias. the dnas from these hyperplasias had no evidence of activation of the c-h-ras-1 gene. one of the fifte ... | 1988 | 2842717 |
| a milk protein gene promoter directs the expression of human tissue plasminogen activator cdna to the mammary gland in transgenic mice. | whey acidic protein (wap) is a major whey protein in mouse milk. its gene is expressed in the lactating mammary gland and is inducible by steroid and peptide hormones. a series of transgenic mice containing a hybrid gene in which human tissue plasminogen activator (tpa) cdna is under the control of the murine wap gene promoter had previously been generated. in this study, 21 tissues from lactating and virgin transgenic female mice containing the wap-tpa hybrid gene were screened for the distribu ... | 1988 | 2842753 |
| inducible expression of herpes simplex virus type 2 glycoprotein gene gg-2 in a mammalian cell line. | the gg-2 glycoprotein gene of herpes simplex virus type 2 (hsv-2) was cloned into the mammalian expression vector pmsg under the control of the inducible mouse mammary tumor virus promoter. transfection of this cloned gg-2 construct into nih 3t3 cells resulted in the stable expression of gg-2 upon induction with dexamethasone. in addition, the 104,000-molecular-weight (104k) and 72k gg-2 precursors as well as the 34k secreted component were generated in the transformed cells. the synthesis of gg ... | 1988 | 2843667 |
| progesterone induction of metallothionein-iia gene expression. | expression of the metallothionein gene is known to be induced by glucocorticoids in a variety of cells. here we show that in human cell lines containing functional progesterone receptors, the endogenous metallothionein-iia (hmtiia) gene is inducible by the synthetic progestins r5020 and medroxy-progesterone acetate. that this effect reflects a direct interaction with the metallothionein gene is supported by our finding that the partially purified progesterone receptor binds to the promoter regio ... | 1988 | 2843758 |
| unspecific and sequence-specific deoxyribonucleic acid binding of the partially purified human progesterone receptor. | the progesterone receptor (pr) was partially purified from t47d human breast cancer cells by sequential chromatography on phosphocellulose, heparin-sepharose, and dna-cellulose. heparin-sepharose chromatography resulted in an efficient conversion of the receptor to a dna-binding form (activation) since more than 85% of the 3h-r5020 labeled eluate from heparin-sepharose was retained on dna-cellulose and since the cytosolic 8s receptor was converted to a 4s moiety after chromatography on heparin-s ... | 1988 | 2843763 |
| molecular events during b lymphocyte differentiation. induction of endogenous mouse mammary tumor proviral envelope transcripts after b cell stimulation. | we have identified a gene whose expression appears to be associated with a late stage in the differentiation of b lymphocytes into antibody secreting cells, as shown by using the inducible b cell lymphoma, ch12. restriction mapping and partial sequencing of a cdna clone isolated by subtraction analysis demonstrated that the clone, sc34, represents an envelope (env) gene transcript of a mouse mammary tumor virus (mmtv). in ch12 cells and in normal b cells, levels of mmtv rna were increased after ... | 1988 | 2844901 |
| proto-neoplasia revisited: the molecular biology of mouse mammary hyperplasia. | the mouse mammary tumor model is a well characterized multistep tumor system which has been used to study characteristics of protoneoplastic and neoplastic lesions of the breast. the ability to transplant mammary epithelial tissue or cells into gland cleared fat pads makes this system more powerful and versatile than most tumor models. transplantability has provided sufficient tissue to allow sequential molecular analysis of protoneoplastic tissue, making studies of clonality and oncogene activa ... | 1988 | 2845853 |
| modulation in the expression of murine mammary tumor virus, ras proto-oncogene, and of alveolar hyperplasia by fatty acids in mouse mammary explant cultures. | hyperplastic alveolar nodule, present in the young adult non-lactating but mammary tumor virus harbouring mice (riii), are biologically active precursor lesions which form mammary tumors at certain age. using mammary explant cultures from these mice as a model for preneoplastic hyperplasia, we have examined the effects of various fatty acids on the changes in the cellular and molecular markers in vitro. we find that exposure of cultures to omega-6 fatty acids results in -13 fold increase on rt a ... | 1988 | 2845856 |
| intervention of t-cells in transportation of mouse mammary tumor virus (milk factor) to mammary gland cells in vivo. | using balb/c nu/nu, balb/c nu/nufc3h (balb/c nu/nu mice raised by c3h/hen foster mother), balb/c thymus-engrafted balb/c nu/nufc3h, balb/c nu/+, and balb/c nu/+fc3h mice, we examined what kinds of cells are carriers of blood-borne mouse mammary tumor virus (b-mmtv). a radioimmunoassay and an immunoperoxidase assay revealed the presence of mmtv-gp52 antigen in the mammary glands of all balb/c nu/+fc3h and balb/c thymus-engrafted balb/c nu/nufc3h mice (more than 60 days old) but only of some balb/ ... | 1988 | 2846153 |
| specific glucocorticoid receptor binding to dna reconstituted in a nucleosome. | we have reconstituted a nucleosome with core histones from rat liver using a restriction fragment containing a sequence from the mouse mammary tumour virus (mtv) long terminal repeat (ltr). this sequence harbours glucocorticoid responsive elements (gres) which mediate glucocorticoid hormone induction of transcription from the mtv promoter via glucocorticoid receptor (gr) binding. exonuclease iii and dnase i footprinting demonstrated that the reconstituted nucleosome was specifically located betw ... | 1988 | 2846275 |
| elevation of mouse mammary tumor virus envelope glycoprotein (gp52) by growth factors. | murine mammary tumor cells (c3h mm5mt/cl and b9) were grown in serum-free culture to examine the effects of different polypeptide growth factors on viral glycoprotein (gp52) release into extracellular culture fluids. epidermal growth factor (egf) elevated extracellular virion-associated and soluble gp52 levels of mouse mammary tumor virus producer and nonproducer cells. while egf effectively and consistently elevated gp52 levels at 20 ng/ml, fibroblast growth factor was less effective, and plate ... | 1988 | 2846465 |
| mouse mammary tumor virus proviruses in t-cell lymphomas lack a negative regulatory element in the long terminal repeat. | the nucleotide sequences of long terminal repeats (ltrs) from several mouse mammary tumor virus (mmtv) proviruses acquired in mouse t-cell lymphomas were determined. all mmtv proviruses cloned from a c57bl/6 lymphoma contained an identical ltr deletion of 491 base pairs (approximately -655 to -165), whereas an mmtv provirus from a balb/c t-cell lymphoma had a 430-base-pair deletion in the same u3 region. mmtv proviruses with ltr deletions were acquired in these tumors 10 times more frequently th ... | 1988 | 2846876 |
| cooperative transforming activities of ras, myc, and src viral oncogenes in nonestablished rat adrenocortical cells. | early-passage rat adrenocortical cells were infected with kirsten murine sarcoma virus and mmcv mouse myc virus, two retroviruses carrying the v-ki-ras and v-myc oncogenes, respectively. efficient morphological transformation required coinfection with the two viruses, was dependent on the presence of high serum concentrations, and was not immediately accompanied by growth in soft agar. the doubly infected cells coordinately acquired the capacity for anchorage- and serum-independent growth during ... | 1988 | 2846881 |
| a model for hormone receptor binding to the mouse mammary tumour virus regulatory element based on hydroxyl radical footprinting. | the mouse mammary tumour virus long terminal repeat region contains regulatory sequences able to mediate transcriptional induction by different steroid hormones. two clusters of binding sites for the glucocorticoid and the progesterone receptors have been identified in the region between -70 and -190, the so called hormone responsive or regulatory element. to understand the molecular details of the interaction between the receptors and the dna we have used the high resolution technique of hydrox ... | 1988 | 2848219 |
| construction of a clonable, infectious, and tumorigenic mouse mammary tumor virus provirus and a derivative genetic vector. | molecular genetic studies of mouse mammary tumor virus (mmtv) have been hampered by the difficulty of cloning proviruses of milk-borne strains because of inhibitory sequences located in the gag gene. to surmount this barrier we have constructed a hybrid mmtv provirus composed of clonable 5' sequences (encompassing gag) from an endogenous mmtv provirus of c3h mice (mtv-1) and 3' sequences from the milk-borne strain of mmtv in c3h mice, mmtv(c3h). virions produced from xc cells transfected with th ... | 1988 | 2849114 |
| towards an idiotype vaccine against mammary tumors. induction of an immune response to breast cancer-associated antigens by anti-idiotypic antibodies. | previously we have reported on the production of two sets of human monoclonal antibodies reacting with mouse mammary tumor virus (mmtv) and human mammary tumor virus (humtv) cross-reacting antigens. b11 is a monoclonal igg generated by the human-human hybridoma technique using axillary lymph node of breast cancer patients. 4.6/6 is a monoclonal igg established by the mouse-human hybridoma procedure using peripheral blood lymphocytes of a healthy investigator working with the breast cancer cell l ... | 1988 | 2849550 |
| requirement for the simian virus 40 small tumor antigen in tumorigenesis in transgenic mice. | to examine the role of simian virus 40 (sv40) large t and small t antigens in tumorigenesis in animals, we generated transgenic mice which expressed either both the sv40 large t and small t antigens or the sv40 large t antigen alone under the control of the mouse mammary tumor virus long terminal repeat. the mouse mammary tumor virus long terminal repeat directs the expression of transgenes in ductal epithelial cells of several organs, including the mammary gland, lung, and kidney, and in lympho ... | 1988 | 2850490 |
| variable responsiveness of hormone-inducible hybrid genes in different cell lines. | altered steroid responsiveness leads to various pathological conditions and is a particular problem for the treatment of cancers arising in steroid-sensitive cells. to develop cellular model systems for the analysis of the molecular mechanisms mediating altered steroid responses, we have analyzed the inducibility of a steroid-responsive promoter in different cell lines. in vitro constructs containing the mouse mammary tumor virus promoter fused to the herpes simplex virus thymidine kinase gene o ... | 1988 | 2851100 |
| negative regulation of transcription in vitro by a glucocorticoid response element is mediated by a trans-acting factor. | in vitro experiments with cell extracts prepared from a mouse mammary epithelial cell line demonstrated that a cis-acting glucocorticoid response element (gre) of the mouse mammary tumor virus represses transcription from its homologous promoter. competition transcription experiments, in which a molar excess of a restriction fragment that contains the gre is added to the cell-free assay, revealed that a nuclear factor mediates in trans the negative regulation of mammary tumor virus transcription ... | 1988 | 2851730 |
| concentration of retroviruses by low-speed centrifugation. | concentration of retroviruses from volumes of up to 6 liters of medium by low-speed centrifugation is described. in contrast to pelleting, no damage or aggregation of particles was observed. surface glycoproteins were also fully preserved. this method enables simple handling of relatively large volumes of medium. highly purified mouse mammary tumor virus (mmtv) was obtained and its transframe protein p30 in sds-page was recognized as a double band. | 1988 | 2851744 |
| chromatin structure of hormone-responsive moloney murine leukemia virus proviruses that contain sequences from mouse mammary tumor virus. | the chromatin structure of chimeric moloney murine leukemia viruses (m-mulvs) containing a glucocorticoid response element (gre) from mouse mammary tumor virus (mmtv) inserted into the long terminal repeat (ltr) was investigated. nuclear run-on assays indicated that transcription from the chimeric proviruses was induced 2- to 4-fold by dexamethasone. the wild-type m-mulv 5' ltr contained a dnase i hypersensitive (hs) site at the tata sequences, as well as four sites in the enhancer region. the c ... | 1988 | 2852418 |
| differential detection of murine mammary tumor virus constituents by immuno-electron microscopy. | | 1988 | 2855364 |
| dual regulation of protein maturation in viral infected rat htc hepatoma cells by glucocorticoids and progesterone. | dexamethasone, a synthetic glucocorticoid, is required for full posttranslational maturation of mouse mammary tumor virus (mmtv) phosphoproteins and glycoproteins in m1.54 cells, a viral infected rat hepatoma (htc) cell line. pulse-chase radiolabeling with [35s]methionine revealed that steroids with known glucocorticoid activity (such as dexamethasone and hydrocortisone) regulated the maturation of both mmtv polyproteins in a manner proportional to their occupancy for glucocorticoid receptors an ... | 1987 | 2856402 |
| mouse lymphoma cell variants with genetically dominant alterations in the maturation of viral glycoproteins. | the appearance of mouse mammary tumor virus (mmtv) glycoproteins on the surface of infected mouse lymphoma cells is regulated by glucocorticoid hormones. the hormone stimulates transcription of the proviral genes and is also required for maturation of viral proteins. we have reported earlier the isolation of variant cell lines with altered patterns of cell-surface expression of the mmtv antigens. one type of variant expresses high levels of viral glycoproteins on the cell surface in a constituti ... | 1987 | 2856407 |
| mechanism of dexamethasone 21-mesylate antiglucocorticoid action: ii. receptor-antiglucocorticoid complexes do not interact productively with mouse mammary tumor virus long terminal repeat chromatin. | we have studied the interaction of covalent dexamethasone 21-mesylate (dm) labeled, activated glucocorticoid receptor with mouse mammary tumor virus (mmtv) chromatin. studies were performed on a murine cell line (904.13) which contains 200 copies per cell of a mmtv long terminal repeat (ltr) v-rash casette mobilized on bovine papilloma virus based episomes. dm binds covalently to glucocorticoid receptors and displays almost full antagonist activity in this cell line. in situ transcription extens ... | 1987 | 2856414 |
| a new cell system for the study of mouse mammary tumour virus. | a stable cell line derived from mammary gland cancer of djungarian hamster is proposed for the study of oncogenic properties of mouse mammary tumour virus (mmtv). the conditions of infection and expression of the viral genome in this cell line are described in addition to the chromosomal composition or the original and infected cells. the mmtv-infected cells showed increased colony formation in semi-solid media. the advantages of the new cell system are discussed. | 1985 | 2859767 |
| blocked coated pits in att20 cells result from endocytosis of budding retrovirions. | att20 cells support the replication of two endogenous retroviruses, a murine leukemia virus and a mouse mammary tumor virus. on glass or plastic substrates, att20 cells grow in clumps. in this situation, retroviruses budding from the plasma membrane of one cell can, on rare occasions, be invested by coated pits in the plasma membranes of contiguous cells. these pits can invaginate to depths of 2,000-4,000 a within the cytoplasm drawing with them the viral buds which remain connected to their par ... | 1985 | 2865267 |
| retroviral insertional mutagenesis in murine mammary cancer. | we are attempting to identify cellular oncogenes activated in mammary tumours by using the mouse mammary tumour virus (mmtv) as an insertional mutagen. mmtv, a retrovirus lacking a host cell-derived viral oncogene, induces adenocarcinomas of the mammary gland after a long latency period. the tumours are clonal outgrowths of cells carrying one or more integrated mmtv proviral copies. we have cloned an integrated mmtv provirus with its adjacent chromosomal dna and we have established that the inse ... | 1985 | 2866522 |
| molecular cloning and characterization of mouse mammary tumor proviruses from a t-cell lymphoma. | five mouse mammary tumor virus proviruses and their flanking cellular dna sequences have been cloned from a transplanted c57bl/6 (b6) t-cell lymphoma containing additional copies of mouse mammary tumor virus dna. characterization of these proviruses and their flanking dna indicates that b6 lymphomas contain many newly integrated mouse mammary tumor virus copies synthesized by a mechanism(s) which generates polymorphism or deletions or both. | 1986 | 2867232 |