Mutational analysis of simian virus 40 T antigen: stimulation of cellular DNA synthesis and activation of rRNA genes by mutants with deletions in the T-antigen gene.

The biological activity of several deletion mutants of simian virus 40, cloned in pBR322, was determined. Three functions of the simian virus 40 A gene were studied: (i) the ability to express T antigen; (ii) the ability to induce cell DNA replication; and (iii) the ability to reactivate silent rRNA genes in hybrid cells. Recombinant plasmid DNA was introduced into cells by manual microinjection or by transfection. The results (together with previous reports) indicate that the critical sequences for these three functions are located separately on the simian virus 40 A gene, as follows: (i) the sequences necessary for the detection of the common antigenic determinant of T antigen extend from nucleotide 4147 to nucleotide 4001 (map units 0.45 to 0.42); (ii) the sequences critical for the stimulation of cell DNA synthesis extend from nucleotide 4327 to nucleotide 4001 (map units 0.49 to 0.42); and (iii) those critical for the reactivation of rRNA genes extend approximately from nucleotide 3827 to nucleotide 3526 (map units 0.39 to 0.33).