Partial characterization of temperature-sensitive mutants of pseudorabies virus

Abstract

Forty-seven temperature-sensitive mutants of pseudorabies virus, isolated after mutagenesis with BUdR, uv, or nitrosoguanosine, were partially characterized with respect to phenotypic expression at the nonpermissive temperature and were placed into complementation groups. Thirty-two of these mutants had nonoverlapping complementation patterns; they were placed into 19 complementation groups. Cells infected with mutants belonging to 10 of these complementation groups do not synthesize viral DNA at the nonpermissive temperature, i.e., the mutants are DNA-. Mutants in the other nine complementation groups are DNA +. Two of the DNA − mutants do not induce detectable levels of DNA polymerase activity at the nonpermissive temperature. One of the polymerase mutants is arrested at the immediate-early phase of infection and does not induce any early enzyme (or protein); the other mutant appears to be mutated in the polymerase gene itself. With the exception of one DNA - mutant and four DNA + mutants (belonging to three complementation groups), cells infected with all the mutants assemble empty capsids; none of the mutant-infected cells assemble full capsids at the nonpermissive temperature. Thus, one-half of the mutants are defective in functions involving DNA synthesis; the others in late function. All of the mutants are mutated in functions preceding the process of nucleocapsid envelopment.