Cell type specific activity and cellular transactivators of avian retroviral long terminal repeat enhancers

The Rous sarcoma virus (RSV) long terminal repeat (LTR) and the highly related LTR from avian leukosis virus (ALV) contain strong transcriptional enhancers. Animals infected with non-acute viruses containing either of these LTRs develop primarily B cell lymphomas. Experiments presented here demonstrate that the RSV LTR is approximately 60 times more active transcriptionally in avian B cells than in fibroblasts, suggesting that the cell type specificity of disease induced is primarily determined by cell type specific differences in the level of LTR activity. Deletion analysis of the RSV LTR has identified the 5...