Transcription and replication of vesicular stomatitis virus: effects of temperature-sensitive mutations in complementation group IV.

Temperature-sensitive (ts) mutants of vesicular stomatitis virus belonging to the RNA(-) complementation group IV were investigated under various conditions to study both their RNA and protein syntheses. In infected cells maintained at 39.2 C, viral RNA species were recovered only in the 13 to 15S region of the gradient in an amount depending on the ts mutant used. In the presence of cycloheximide at 39.2 C, the primary transcription was deficient, especially for 28S mRNA production. When mutant-infected cells were shifted to nonpermissive temperature, a shutoff of 28S mRNA synthesis occurred as a general feature. On the contrary under this condition, the two mutants chosen, ts IV100 and ts IV111, behaved very differently in their 13 to 15S and 38S RNA production. However, treatment with cycloheximide at the time of the transfer to 39.2 C resulted in a similar recovery of 13 to 15S RNA in both mutants, whereas the 28S remained very depressed. The viral proteins synthesized by cells infected with the same two mutants also showed a distinct pattern, especially regarding the N protein; a correlation between 38S RNA and protein N syntheses was tentatively drawn. The whole set of data suggested that the lesion in group IV mutants concerned a viral structural protein required for the process of in vivo transcription and which probably intervened in the replication mechanism.