Coping with replication 'train wrecks' in Escherichia coli using Pol V, Pol II and RecA proteins.

DNA replication machineries tend to stall when confronted with damaged DNA template sites, causing the biochemical equivalent of a major 'train wreck'. A newly discovered bacterial DNA polymerase, Escherichia coli Pol V, acting in conjunction with the RecA protein, can exchange places with the stalled replicative Pol III core and catalyse 'error-prone' translesion synthesis. In contrast to Pol V-catalysed 'brute-force, sloppier copying', another SOS-induced DNA polymerase, Pol II, plays a pivotal role in an 'error-free', replication-restart DNA repair pathway and probably involves RecA-mediated homologous recombination.