DNA sequence alterations responsible for the synthesis of thermosensitive VP1 in temperature-sensitive BC mutants of simian virus 40.

The segment of simian virus 40 (SV40) genome which is recognized as the BC domain encodes for the COOH-terminal end of the SV40 major capsid protein VP1. Mutations in this domain lead to the synthesis of a thermosensitive VP1 which fails to assemble mature SV40 at the nonpermissive temperature. We determined the DNA sequences of eight BC mutants and compared them with the DNA sequences of wild-type SV40, polyomavirus, and BK virus. We found that BC11 and BC223 mutations result from changes in nucleotide residues 2367 (A to C) and 2084 (C to T), respectively. The others (i.e., BC208, BC214, BC216, BC217, BC248, and BC274) share the same point mutation at nucleotide 2354 (C to T). These mutations resulted in the following changes: Lys to Thr, His to Tyr, and Pro to Ser at VP1 amino acid residues 290, 196, and 286, respectively.