Differential affinities of simian virus 40 large tumor antigen for DNA.

Abstract

The binding of SV40 large tumor (T) antigen to DNA was analyzed using the salt-sensitive affinities of the protein for various DNA immobilized on cellulose. At least 2 types of interactions could be distinguished that differed in their stability. Higher salt concentrations were required to elute T antigen from SV40 DNA than from calf thymus DNA; even greater salt concentrations were required for the elution of T antigen from multiorigin SV40 DNA compared to wild-type SV40 DNA. This would indicate that T antigen can bind weakly or strongly to DNA, depending on the DNA sequence. A greater proportion of rapidly labeled or newly synthesized T antigen binds more efficiently and tightly to multiorigin SV40 DNA than to long-labeled or older forms of T antigen. This approach can be utilized not only to distinguish between different forms of T antigens which vary in their affinities for DNA but also for rapidly obtaining highly enriched T antigen preparations.