CHANGES IN THE NUCLEOSOMAL STRUCTURE OF THE MAREKS-DISEASE VIRUS GENOME IN LYMPHOBLASTOID CELL-LINE MDCC-MSB1 INDUCED BY 5-AZACYTIDINE

Marek's disease virus (MDV) DNA in latently infected lymphoblastoid ce ll lines is considerably methylated. Treatment of the MDV-derived lymp hoblastoid cell lines MDCC-MSB1 (MSB1) and MDCC-RP1 (RP1) with 5-azacy tidine (5-AzC) results in hypomethylation of MDV DNA. An increase in m RNA from certain portions of MDV DNA, including the BamHI-H region, wa s observed in 5-AzC-treated MSB1 cells, but not in the agent-treated R P1 cells. After the treatment of cells with 5-AzC, a site hypersensiti ve to digestion with DNaseI appeared in the BamHI-H region of MDV DNA in MSB1 but not in RP1. These results suggested that the enhancement o f mRNA synthesis by 5-AzC is associated with changes in the nucleosoma l structure of MDV DNA in lymphoblastoid cell. line MSB1.