THE ORIGIN DNA-BINDING AND SINGLE-STRANDED DNA-BINDING DOMAINS OF SIMIAN-VIRUS-40 LARGE T-ANTIGEN ARE DISTINCT

Little is known about the ability of simian virus 40 (SV40) T antigen to bind single-stranded DNA. We demonstrate here that a mutant (259-70 8) missing the first 258 amino acids of T antigen and its origin-bindi ng domain bound single-stranded DNA at close to normal levels, whereas a mutant containing only the first 259 amino acids failed to bind any single-stranded DNA. The 259-708 mutant also assembled into high-mole cular-weight oligomers in the presence of single-stranded DNA. Its ATP ase activity was stimulated by single-stranded DNA similarly to the wi ld type (WT). Furthermore, WT T antigen's ability to bind to single-st randed DNA was inhibited by the binding of two monoclonal antibodies t hat recognize a region after residue 362. These results show that the domain responsible for binding to single-stranded DNA is completely se parate from the origin-binding domain.