Mutational analysis of the simian virus 40 replicon: pseudorevertants of mutants with a defective replication origin.

AUTOR(ES)

Shortle, D R

RESUMO

The circular genome of simian virus 40 is a model mammalian replicon, containing a unique origin of replication (ori) and coding for a protein (SV40 T antigen) known to be involved in initiation of viral DNA replication and to bind in vitro to the origin region. Mutations within the ori sequence lead to defective viral DNA replication and the formation of small viral plaques after infection of a cell monolayer. Second-site revertants (pseudorevertants) of ori mutants were isolated by random local mutagenesis of mutant DNA followed by transfection of cultured cells and the selection of large plaques. In each case, reversion of the plaque phenotype was associated with an increased rate of viral DNA replication. The second-site mutations that suppressed the replication defects were localized by in vitro recombination or marker rescue experiments to the gene for T antigen. Their map positions differ from those of previously described T antigen mutants, possibly reflecting a specific ori-binding domain of T antigen. From these results we infer that T antigen interacts with the ori signal during virus development as it does in vitro and that this interaction regulates the rate of viral DNA replication.

Documentos Relacionados

• Territorial limits and functional anatomy of the simian virus 40 replication origin.
• Expression of early genes of origin-defective mutants of simian virus 40.
• Cooperative assembly of simian virus 40 T-antigen hexamers on functional halves of the replication origin.
• Transcription factor Oct1 binds to the AT-rich segment of the simian virus 40 replication origin.
• The replication activation potential of selected RNA polymerase II promoter elements at the simian virus 40 origin.