Biological activities of deletion mutants of simian virus 40.

Mutants of Simian virus 40 (SV40) with large deletions in the early or late regions of the genome were tested for biological activity. Deletion mutants lacking portions of both late genes (B/C and D), but with an intact early genomic segment, were able to induce T antigen in infected cells, replicate their DNA in the absence of helper virus, stimulate thymidine incorporation into cellular DNA, and transform mouse and hamster cells. Cells transformed by late deletion mutants were shown to contain the mutant genome by a fusion-complementation rescue procedure. Deletion mutants lacking substantial portions of the early genomic region, including those segments where tsA mutants map, lacked all of the above activities. However, both early and late deletion mutants interfered with SV40 DNA replication.