Structure of the SSB-DNA polymerase III interface and its role in DNA replication.

ABSTRACT: Interactions between single-stranded DNA-binding proteins (SSBs) and the DNA replication machinery are found in all organisms, but the roles of these contacts remain poorly defined. In Escherichia coli, SSB's association with the ? subunit of the DNA polymerase III holoenzyme has been proposed to confer stability to the replisome and to aid delivery of primers to the lagging-strand DNA polymerase. Here, the SSB-binding site on ? is identified crystallographically and biochemical and cellular studies delineate the consequences of destabilizing the ?/SSB interface. An essential role for the ?/SSB interaction in lagging-strand primer utilization is not supported. However, sequence changes in ? that block complex formation with SSB lead to salt-dependent uncoupling of leading- and lagging-strand DNA synthesis and to a surprising obstruction of the leading-strand DNA polymerase in vitro, pointing to roles for the ?/SSB complex in replisome establishment and maintenance. Destabilization of the ?/SSB complex in vivo produces cells with temperature-dependent cell cycle defects that appear to arise from replisome instability.

SUBMITTER: Marceau AH 

PROVIDER: S-EPMC3199393 | biostudies-literature | 2011 Aug

REPOSITORIES: biostudies-literature