Extent of Transcription of Mouse Sarcom

The DNA product obtained from the en- dogenous RNA-directed DNA polymerase (deoxynucleo- sidetriphosphate: DNA deoxynucleotidyltransferase, EC 2.7.7.7) reaction of the Moloney sarcoma:leukemia viruses produced by the 78 A-1 cell line was analyzed and charac- terized. The extent of transcription of viral 70S RNA was measured by RNA DNA hybridization ("P-viral RNA-'H product DNA). No double-stranded DNA was obtained. The product consisted of 95-99% single-stranded DNA with an average length of 200 nucleotides. In contrast to the re- sults reported with avian and other RNA oncogenic viruses, it was found that the entire 70S viral RNA genome was transcribed into DNA pieces and that a small excess of the product DNA was sufficient to anneal the 70S RNA and render it totally resistant to single-stranded-specific en- zyme digestion.