Binding of simian virus 40 a protein to DNA with deletions at the origin of replication.

Previous studies with wild-type simian virus 40 DNA have shown that the sequence 5'-GAGGC-3' directs the binding of A protein (T antigen). The functional origin of replication contains four recognition pentanucleotides each of which is separated by a single base pair and arranged a two pairs of direct repetitions that are inverted relative to each other. Analysis of A protein binding to a series of nonviable mutants progressively deleting these contact sites leads to the following conclusions: (i) stable binding of subunits of A protein to three origin pentanucleotides is not sufficient for the initiation of DNA replication, (ii) the stability of DNA binding depends on interactions between bound protein subunits, and (iii) a single pentanucleotide is sufficient to bind and orient a subunit of A protein.