Inhibition of the rous sarcoma virus long terminal repeat-driven transcription by in vitro methylation: different sensitivity in permissive chicken cells versus mammalian cells

Rous sarcoma virus (RSV) enhancer sequences in the long terminal repeat (LTR) have previously been shown to be sensitive to CpG methylation. We report further that the high density methylation of the RSV LTR-driven chloramphenicol acetyltransferase reporter is needed for full transcriptional inhibit...

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Bibliographic Details
Published in:Virology (New York, N.Y.) N.Y.), 1999-03, Vol.255 (1), p.171-181
Main Authors: Hejnar, J, Plachý, J, Geryk, J, Machon, O, Trejbalová, K, Guntaka, R V, Svoboda, J
Format: Article
Language:English
Subjects:
3T3 Cells
Animals
Avian Sarcoma Viruses - genetics
Cell Line
Chick Embryo
Chickens
Cricetinae
DNA Methylation
DNA, Viral
Gene Expression Regulation, Viral
Mice
Moloney murine leukemia virus - genetics
Oncogene Protein pp60(v-src) - genetics
Oncogene Protein pp60(v-src) - metabolism
Proviruses - genetics
Rous sarcoma virus
Sarcoma, Experimental
Terminal Repeat Sequences
Time Factors
Transcription, Genetic
Transfection
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Summary:Rous sarcoma virus (RSV) enhancer sequences in the long terminal repeat (LTR) have previously been shown to be sensitive to CpG methylation. We report further that the high density methylation of the RSV LTR-driven chloramphenicol acetyltransferase reporter is needed for full transcriptional inhibition in chicken embryo fibroblasts and for suppression of tumorigenicity of the RSV proviral DNA in chickens. In nonpermissive mammalian cells, however, the low density methylation is sufficient for full inhibition. The time course of inhibition differs strikingly in avian and mammalian cells: although immediately inhibited in mammalian cells, the methylated RSV LTR-driven reporter is fully inhibited with a significant delay after transfection in avian cells. Moreover, transcriptional inhibition can be overridden by transfection with a high dose of the methylated reporter plasmid in chicken cells but not in hamster cells. The LTR, v-src, LTR proviral DNA is easily capable of inducing sarcomas in chickens but not in hamsters. In contrast, Moloney murine leukemia virus LTR-driven v-src induces sarcomas in hamsters with high incidence. Therefore, the repression of integrated RSV proviruses in rodent cells is directed against the LTR.
ISSN:0042-6822
DOI:10.1006/viro.1998.9597