Characterization of three complementation groups of vesicular stomatitis virus

Abstract

The complementation properties of 25 temperature-sensitive mutants of VSV have been tested by measuring the yield of virus in mixedly infected cells at the nonpermissive temperature, 38°C. Two of the mutants, ts10W and ts16BW, complement all the mutants except each other and therefore form one distinct complementation group, A. Two other mutants, ts12W and ts29W do not complement each other but complement nearly all the other mutants and have been assigned to a second complementatation group, B. A group of six mutants, all of which show an increased heat lability of the virion, show no complementation within the group and have been assigned to a third group, C. Most of the remaining mutants complement at least one member of each of groups A, B, and C but have not yet been assigned to other groups since many of the crosses of these mutants with group C mutants fail to show complementation. Virus-specific RNA synthesis in L cells infected with the various mutants was investigated by measuring the incorporation of 14C-labeled uridine. All the group C mutants show little or no virus-specific RNA synthesis at 38°C, even at high multiplicities, suggesting that in these mutants the defect is in the structural RNA polymerase. The two mutants of group A show little or no virus-specific RNA synthesis at 38°C at low input multiplicities but considerable RNA synthesis at high multiplicities. Since this synthesis is not reduced by the presence of puromycin it would appear that these mutants have a structural polymerase which is functional at 38°C but are defective in some other type of RNA synthesis. Mutants of group B show RNA synthesis at 38°C comparable to that of the wild type at all multiplicities but fail to produce infectious virus after a shift from 30 to 38°C at any time during the growth cycle. The defect in these mutants therefore appears to be in some function such as the synthesis or assembly of structural proteins.