Induction of mouse type-C virus by translational inhibitors: evidence for transcriptional derepression of a specific class of endogenous virus.

Cabradilla, Cirilo D.; Robbins, K C; Aaronson, Stuart A.

doi:10.1073/pnas.73.12.4541

Cited by 23 publications

(9 citation statements)

References 28 publications

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“…1 (a). The plateau value, 70%, is consistent with literature values for this type of hybridization (Callahan et al, 1975;Cabradilla et al, 1976). Background hybridization was consistently 8%, representing 3 % more than the S 1-resistant fraction of cDNA assayed in the absence of RNA.…”

Section: Transcriptional Control Of Endogenous Virus Genes Insupporting

confidence: 89%

Transcriptional Control of Endogenous Virus Genes in Murine Lymphocytes

Moroni

1981

Journal of General Virology

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Section: Transcriptional Control Of Endogenous Virus Genes Insupporting

confidence: 89%

Transcriptional Control of Endogenous Virus Genes in Murine Lymphocytes

Moroni

1981

Journal of General Virology

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“…posed that cycloheximide inhibited degradation of the enzyme (perhaps by depleting an intracellular protease). On the other hand, the effect of cycloheximide on the induction of mouse C-type viruses may result from a decrease in the amount of a transcriptional repressor (Cabradilla et al, 1976).…”

Section: Discussionmentioning

confidence: 99%

Superinduction by cycloheximide of mitogen‐induced secreted proteins produced by Balb/c 3T3 cells

Hamilton

Nilsen-Hamilton

Adams

1985

Journal Cellular Physiology

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We describe here some of the characteristics of the regulation of a group of secretory proteins whose secreted levels rise within 2-4 h of adding fibroblast growth factor (FGF), epidermal growth factor (EGF), or serum to quiescent Balb/c 3T3 cells. The levels of these secretory proteins are regulated similarly to the interferons. When cycloheximide is present during the induction period, the amounts of [35S]methionine incorporated into five of these proteins that we have called "superinducible proteins" (SIPs) is increased 2-5-fold. Superinduction of the SIPs is seen also in response to polyribol-polyriboC, the classical inducer of interferons. None of the SIPs, however, are immuno-precipitated by anti-beta-interferon antibody. Induction and superinduction of the SIPs is inhibited by actinomycin D. Superinduction occurs at concentrations of cycloheximide that inhibit protein synthesis by at least 85%. The SIPs are not major intracellular proteins; they are barely detectable in cellular fractions. Their induction is, however, correlated with the ability of the polypeptide growth factor to stimulate DNA synthesis; EGF, FGF, and serum induce the SIPs, whereas insulin does not, and insulin alone weakly stimulates DNA synthesis in these cells. Because FGF, EGF, and serum cause the SIPs to be produced at concentrations of cycloheximide that inhibit 85% of bulk protein and DNA synthesis, it follows that the SIPs are produced directly from the action of the growth factor and not as a consequence of increased growth. Although probably not interferons, in analogy to the lymphokines, the SIPs could be a set of autocrine or paracrine factors that rapidly convey the growth or differentiation signal between cells.

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“…Regulation of type C virus gene expression at the transcriptional level has been reported for BALB:virus-I (29) and for ecotropic AKR virus (30 …”

Section: -3fmentioning

confidence: 99%

5-Azacytidine induction of mouse endogenous type C virus and suppression of DNA methylation.

Niwa¹,

Sugahara²

1981

Proc. Natl. Acad. Sci. U.S.A.

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5-Azacytidine was found to induce the expression of BALB:virus-1 and BALB:virus-2 from K-BALB cells and ecotropic endogenous virus from AKR2B cells. Efficiency of the induction was high and comparable to that by 5-bromodeoxyuridine. The level of methylcytosine in newly synthesized DNA was drastically decreased when K-BALB cells were treated with 5-azacytidine. There was an inverse relationship between the level of DNA modification and the frequency of virus expression.Mammalian DNA contains about 2-7% of its cytosine methylated in the 5 position (1). Methylation of DNA was proposed to play a regulatory role in gene expression of eukaryotic cells (2), although the precise mechanism involved is unknown. 5-Azacytidine (5azaCyd), a cytidine analogue with nitrogen in the 5 position, has recently been shown to induce myotube formation in mouse embryonic fibroblast culture (3) and at the same time inhibit methylation of DNA (4).All strains of laboratory mice carry DNA sequences of endogeneous type C viruses in an unexpressed form (5). Expression of the endogenous viruses can be induced by treatment of cells with various agents. These agents include halogenated pyrimidines such as 5-bromodeoxyuridine (BrdUrd) and 5-iododeoxyuridine (IdUrd) (6, 7), inhibitors of protein synthesis such as cycloheximide and puromycin (8), an amino acid analogue (9), and DNA-damaging agents (10-12). In this communication, we report that 5-azaCyd induces expression of endogenous virus as efficiently as does BrdUrd, one ofthe most potent inducers so far studied. Our data also indicate that DNA modification might be involved in the repression of endogenous virus genome in mammalian cells. MATERIALS AND METHODSCell Culture. All cultures were grown in Eagle's minimal essential medium supplemented with 10% heat-inactivated calf serum. K-BALB cells (13) X 10"l becquerels) for ['4C]thymidine, 2 pug/ml for 5-azaCyd, 30 ,ug/ml for BrdUrd, or 20 pg/ml for cycloheximide. The dish receiving ['4C]thymidine was incubated for 10 min and the cells were treated with trypsin. Appropriate numbers of the cells were filtered onto glass-fiber filters. The filters were washed with 5% trichloroacetic acid and with ethanol. Radioactivity incorporated was used as a measure ofDNA synthesis. The dishes were incubated for 5 hr with various inducers and assayed for virus production by the procedure described above.Base Analysis. Methylcytosine content in the newly synthesized DNA strand was assayed as described by others (4) with minor modifications. K-BALB cells were seeded onto 60-mm dishes at 5 X 105 cells per dish. After overnight incubation, cultures were treated with 5azaCyd in medium. containing [methyl-3H]methionine at 4 ,uCi/ml and [2-'4C]thymidine at 0.005 ,uCi/ml. DNA was collected and hydrolyzed with 60% perchloric acid as described (4). After neutralization with 6 M KOH, 100 ,ul ofthe hydrolysate was spotted onto cellulose thinlayer glass plates together with 5 ,ug each ofmethylcytosine and thymine. The plates were then developed with H2O in dimens...

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Induction of mouse type-C virus by translational inhibitors: evidence for transcriptional derepression of a specific class of endogenous virus.

Abstract: ABSTRACT

Cited by 23 publications

References 28 publications

Transcriptional Control of Endogenous Virus Genes in Murine Lymphocytes

Transcriptional Control of Endogenous Virus Genes in Murine Lymphocytes

Superinduction by cycloheximide of mitogen‐induced secreted proteins produced by Balb/c 3T3 cells

5-Azacytidine induction of mouse endogenous type C virus and suppression of DNA methylation.

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