Biology of simian virus 40 (SV40) transplantation antigen (TrAg): II. Isolation and characterization of additional temperature-sensitive mutants of SV40

Abstract

Fourteen independent temperature-sensitive mutants of simian virus (SV40) were isolated following nitrous acid or hydroxylamine mutagenesis. Three mutants were assigned to the A group and seven to the BC group on the basis of standard qualitative and quantitative complementation assays. Three other mutants did not complement mutants of any complementation group well under standard conditions nor was delayed complementation observed in quantitative assays. However, these mutants were shown to complement members of the A and BC complementation groups but not members of the D group when the qualitative complementation test was modified by allowing the parental virions to uncoat at permissive temperature prior to incubation at 41°. The assignment of these mutants to the D group was substantiated by demonstrating the wild-type infectivity of DNA extracted from cells infected at 33° for growth at 41°. Thirteen of the mutants were tested for the production of tumor (T), capsid (C), virion (V), and major coat protein (VP1) antigens at permissive and nonpermissive temperature by immunofluorescence assays along with mutants which have been described previously by others for comparison. The temperature-sensitive ( ts) mutants isolated in this study produced fully immunoreactive T antigen at both temperatures. None of the tsA mutants produced C, VPl, or V antigens at elevated temperature. The BC mutants isolated in this study all produced T antigen at 41°. These late mutants demonstrated two patterns of expression of virion antigens. One group synthesized C, V, and VP1 at 41° and were indistinguishable from wild type on the basis of antigenic phenotype. A second group showed cytoplasmic and nucleolar fluorescence for C and VPl antigens at the nonpermissive temperature similar to that observed for tsBCll previously. Mutants in this group did not produce V antigen at high temperature.