Functional defects of RNA-negative temperature-sensitive mutants of Sindbis and Semliki Forest viruses
- 1 October 1979
- journal article
- research article
- Published by American Society for Microbiology in Journal of Virology
- Vol. 32 (1) , 19-29
- https://doi.org/10.1128/jvi.32.1.19-29.1979
Abstract
Defects in RNA and protein synthesis of 7 Sindbis virus and 7 Semliki Forest virus RNA-negative, temperature-sensitive mutants were studied after shift to the restrictive temperature (39.degree. C) in the middle of the growth cycle. Only 1 of the mutants, Ts-6 of Sindbis virus, a representative of complementation group F, was clearly unable to continue RNA synthesis at 39.degree. C, apparently due to temperature-sensitive polymerase. The defect was reversible and affected the synthesis of both 42S and 26S RNA equally, suggesting that the same polymerase component(s) is required for the synthesis of both RNA species. One of the 3 Sindbis virus mutants of complementation group A, Ts-4, and 1 RNA.+-. mutant of Semliki Forest virus, ts-10, showed a polymerase defect even at the permissive temperature. Seven of the 14 RNA-negative mutants showed a preferential reduction in 26S RNA synthesis. The 26S RNA-defective mutants of Sindbis virus were from 2 different complementation groups, A and G, indicating that functions of 2 viral nonstructural proteins (A and G) are required in the regulation of the synthesis of 26S RNA. Since the synthesis of 42S RNA continued, these functions of proteins A and G are not needed for the polymerization of RNA late in infection. The RNA-negative phenotype of 26S RNA-deficient mutants implies that proteins regulating the synthesis of this subgenomic RNA must have another function vital for RNA synthesis early in infection or in the assembly of functional polymerase. Several of the mutants having a specific defect in the synthesis of 26S RNA showed an accumulation of a large nonstructural precursor protein with MW of about 200,000. One even larger protein was demonstrated in both Semliki Forest virus- and Sindbis virus-infected cells which probably represents the entire nonstructural polyprotein.This publication has 28 references indexed in Scilit:
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