Orientation of the complementary strands of polyoma virus DNA with respect to the DNA physical map

The chemical polarities of the two strands of polyoma virus DNA with respect to the DNA physical map have been determined by hybridization of restriction endonuclease fragments specifically labeled with [125I]dCMP at their 3' termini to asymmetric polyoma complementary RNA (the product of in vitro transcription of viral DNA by Escherichia coli RNA polymerase). The orientations of the polyoma-specific stable RNA transcripts present in the cytoplasm of productively linfected mouse cells have been deduced from this result: the 5' ends of the early and late viral transcripts map very near the origin of viral DNA replication.