Abstract
RNA polymerase II was purified from mouse Ehrlich ascites tumor cells, and was used to transcribe chromatin from Friend leukemic cells at various stages of induction. The transcription was entirely dependent on exogenous RNA polymerase, and was inhibited by actinomycin D, or a low dose of α-amanitin.
Globin-specific sequences of the transcripts were determined by hybridization of 3H-labeled transcripts with plasmid DNA immobilized on filters. When chromatin from uninduced cells was used, less than 0.01% of the total radioactivity was retained on the globin DNA-filters, whereas about 0.05% was retained when chromatin was made from induced cells. This value was about one-ninth of the content of cytoplasmic globin mRNA which was pulse-labeled in induced cells.
The transcription of whole chromatin or globin genes in chromatin was inhibited almost completely by a rifampicin derivative, but in the case of chromatin, both sense and anti-sense strands of globin genes were transcribed. From these results, it is suggested that isolated chromatin retains some native conformation but is transcribed aberrantly.
