Regulation of transcription of the reovirus genome

Abstract

Previously, it was shown that the major part of the nucleic acid of reovirus is comprised of segments of double-stranded RNA that occur in three size-classes. In the present work the viral double-stranded RNA has been resolved into six classes by electrophoresis on polyacrylamide gel columns. From such analyses it is suggested that the most likely number of segments in the viral genome is ten and, if this is the case, three of the six classes separated by electrophoresis contain single segments of double-stranded RNA. Each class of double-stranded RNA was found to be copied into a corresponding messenger RNA in the infected cell, and the relative amounts of the various messengers was determined by hybridizing with double-stranded RNA and analyzing the products by gel electrophoresis. When such analyses were carried out at different times after infection, it was found that certain classes of messenger RNA were made earlier than others, suggesting a regulation in transcription of the viral genome. Inhibition of protein synthesis by addition of cycloheximide at the time of infection permitted only a limited number of the double-stranded viral RNA segments to be transcribed, suggesting that the early messengers might be synthesized by a pre-existing polymerase.