Topography of polyoma virus messenger RNA molecules.

The different species of polyoma virus-spedific RNA molecules present in the cytoplasm of 3T6 cells 30 hr after viral infection have been characterized by molecular hybridization between nonradioactive polyadenlated RNA, fractionated by sedimentation through sucrose-formamide density gradients, and the 32P-labeled separated strands of restriction endonuclease fragments of polyoma DNA. Two relatively abundant RNA molecules, sedimenting at 16S and at 19S, transcribed from the L strand of the viral DNA, as well as a minor 20S species transcribed from the E strand of the DNA, were detected. The most abundant viral transcript, the 16S RNA molecule, was estimated to be complementary to the 22% of the L-strand DNA extending from 47 to 25 map units. The less abundant 19S L DNA strand transcript included all the sequences present in the 16S RNA and mapped between 68 and 25 map units. The minor 20S RNA molecule was tentatively identified as a transcript of the E-strand DNA from the entire early region of the polyoma genome. These three viral RNA molecules together exhaust greater than 95% of the coding capacity of the viral DNA. A small region of the DNA (4-5%), including the origin of DNA replication, does not appear to determine sequences present among the major stable species of vital mRNA.