Analysis of the defects of temperature-sensitive mutants of vesicular stomatitis virus: intracellular degradation of specific viral proteins

Abstract

The metabolism of viral RNA and proteins were studied in [Chinese hamster ovary, CHO] cells infected with temperature-sensitive mutant strains of vesicular stomatitis virus. Certain viral proteins encoded by the mutant strains, usually the putative mutant protein for the assigned complementation group, were degraded more rapidly at the nonpermissive temperature than were the wild-type proteins. Group III mutants (tsG33, tsM301) encode M [matrix] proteins which are degraded 3 to 4-fold faster than the wild-type protein. This defect cannot be fully rescued by coinfection with wild-type virus, and thus the defect appears to be in the M protein itself. Mutants tsM601 (VI) and tsG41(VI) encode N [nucleocapsid] proteins which are degraded much faster than the wild-type protein and share the property of being defective in replication of viral RNA, suggesting a correlation between these phenotypic properties. The L proteins of tsG11(I) and tsG13(I) are more labile than the wild-type protein at the nonpermissive temperature. The G [glycoprotein] of tsM501(V) did not undergo the change in electrophoretic mobility previously shown to be the result of sialylation, suggesting that it is defective in maturation or glycosylation at the nonpermissive temperature. Three of the mutants previously isolated, tsM502(V), tsM601(VI) and tsM602(VI), were defective in viral RNA synthesis at the nonpermissive temperature. Mutant tsM601(VI) was defective mainly in viral RNA replication, but tsM502(V) appeared to be totally defective for viral RNA transcription and replication at the nonpermissive temperature.