Sloppier copier DNA polymerases involved in genome repair.

When chromosomal replication is impeded in the presence of DNA damage, members of a newly discovered UmuC/DinB/Rev1/Rad30 superfamily of procaryotic and eucaryotic DNA polymerases catalyze translesion synthesis at blocked replication forks. Although these polymerases share sequence elements essentially unrelated to the standard replication and repair enzymes, some of them (such as the SOS-induced Escherichia coli pol V) catalyze 'error-prone' translesion synthesis leading to large increases in mutation, whereas others (an example being the Xeroderma pigmentosum variant gene product XPV pol eta) carry out aberrant, yet nonmutagenic translesion synthesis. Ongoing studies of these low fidelity polymerases could provide new insights into the mechanism of somatic hypermutation, a key element in the immune response.