%0 Journal Article %A Katz, Richard A. %A Mitsialis, S. Alex %A Guntaka, Ramareddy V. %T Studies on the Methylation of Avian Sarcoma Proviruses in Permissive and Non-permissive Cells %D 1983 %J Journal of General Virology, %V 64 %N 2 %P 429-435 %@ 1465-2099 %R https://doi.org/10.1099/0022-1317-64-2-429 %K transcription %K methylation %K avian oncogenic proviruses %I Microbiology Society, %X SUMMARY The extent of methylation of several avian oncogenic proviruses was determined by using the restriction endonucleases HpaII and MspI. The results indicated that the transformation-defective proviruses (RAV-O or B77-td), which are exogenously introduced into avian host cells, were not methylated. However, endogenous proviruses (RAV-O) or ASV proviruses present in non-permissive host cells were found to be partly or completely methylated. The methyl-sensitive restriction endonuclease PvuI, which recognizes a unique site within the long terminal repeat in the ASV genome, failed to cleave proviruses present in several non-permissive host cells. From these results we suggest that modification of the sequence around the PvuI site results in reduced levels of transcription. %U https://www.microbiologyresearch.org/content/journal/jgv/10.1099/0022-1317-64-2-429