Monkey cells transformed by SV40 DNA fragments: flat revertants synthesize large and small T antigens.

Abstract

SV40 causes tumor formation in animals and transforms tissue-culture cells. Experiments with early temperature-sensitive mutants (tsA) indicated that synthesis of wild-type (wt) SV40 large T antigen is required for the induction and maintenance of the transformed state (Martin and Chou 1975; Tegtmeyer 1975; Brugge and Butel 1975; Osborn and Weber 1975). Also, SV40 small T antigen seems to be involved in the process of cell transformation. Early SV40 mutants with deletions between 0.54 and 0.59 map units (e.g. dl884) code for wild-type large T antigen, but for small T antigens of reduced sizes (Bouck et al. 1978; Crawford et al. 1978; Sleigh et al. 1978). These mutants have reduced transformation capacities. However, it is still uncertain which of the early SV40-specific functions attributed to the viral T antigens determine the oncogenicity of SV40.