Abstract
The transcription of polyoma (Py) viral RNA was studied in primary mouse kidney cell cultures (a) during normal, asynchronous infection, (b) under conditions where Py-induced DNA synthesis was inhibited with 5-fluorodeoxyuridine, and (c) after the synchronized onset of Py-induced DNA synthesis. The results obtained suggest that the bulk of Py RNA transcribed after the (asynchronous or synchronized) onset of Py-induced DNA synthesis, designated as "late" Py RNA, corresponds to the polycistronic transcript of most or all of the genetic information contained in a strand of circular Py DNA. The rate at which late Py RNA is transcribed is related to the amount of free Py DNA present in the cultures. Py-infected cultures contain a second, minor component of Py RNA (of one or possibly more species), designated as "early" Py RNA. At least some of this RNA continues to be transcribed if Py-induced DNA synthesis is inhibited with 5-fluorodeoxyuridine and, possibly, also late during normal infection.