Interaction of AD2+D2 protein and simian virus 40 large T antigen with the large tumor antigen binding site I

Abstract

In a lytic infection of a permissive host by SV40, the large tumor antigen (T antigen), which is a product of early transcription of the SV40 A gene, autoregulates its own transcription by binding to SV40 DNA. The DNA region to which T antigen bonds most tightly was synthesized and subsequently introduced into the bacterial plasmid pUC8. The interaction of SV40 T antigen with the DNA duplexes, derived from both chemical synthesis and the recombinant plasmid, were examined by using nitrocellulose filter binding assays. An SV40-adenovirus hybrid protein, AD2+D2 protein, was also tested. The SV40 T antigen bound more tightly than the hybrid protein. Kinetic assays demonstrated that the association rates for the 2 proteins with the DNA binding site were equivalent; however, once formed, the T antigen-DNA complex dissociated more slowly than the AD2+D2 protein-DNA complex.