TRANSCRIPTION OF THE MAREKS-DISEASE VIRUS GENOME IN A NONPRODUCTIVE CHICKEN LYMPHOBLASTOID CELL-LINE

Transcription of the MDV genome in virus-nonproducing MKT-1 cells, a lymphoblastoid cell line derived from a Marek's disease tumor, was studied by analyzing the hybridization kinetics of 3H-labeled MDV DNA with unlabeled RNA extracted from whole cells or from polyribosomes. Twelve to 14% of the viral DNA template was transcribed and only a portion (60-70%) of the viral-specific RNA sequences found in whole cells could be detected in the polyribosomal fraction. When MKT-1 cells were treated with 5′-iododeoxyuridine (IUdR), transcription of the viral genome was induced so that 42% of the MDV DNA template was transcribed. This represents nearly the same degree of transcription as in chicken embryo fibroblasts productively infected with MDV. Viral antigens also were produced following IUdR induction, but viral DNA replication remained restricted. Only 60-70% of the viral-specific RNA sequences found in whole cells of IUdR-treated MKT-1 cells were found in the polyribosomal fraction. The data suggest that there exists within the cell a post-transcriptional control mechanism which selectively excludes certain RNA transcripts from stable association with the polyribosomes and may therefore be responsible, in part, for the repressed expression of viral genetic information in MKT-1 cells. © 1979.