Effects of the cellular p53 protein on Simian‐virus‐40‐T‐antigen‐catalyzed DNA unwinding in vitro

Abstract

It is known that large T antigen, the regulatory protein encoded by Simian virus 40 (SV40), forms tight complexes with the cellular p53 protiens in SV40-transformed rodent cells. Using immunoaffinity procedures we have purified large T antigen and, in separate experiments, and cellular p53 protein. The two proteins formed complexes in vitro which bound well to double-stranded DNA fragments although in a sequence-unspecific manner. Free, uncompleted T antigen readily converted double-stranded DNA into a single-stranded form whereas in vitro-formed p53-T-antigen complexes were inactive in this reaction. We conclude that one function of p53 in SV40-transformed mouse cells could be the inhibition of the replication initiating activity of T antigen.