Structural insights into the assembly of human translesion polymerase complexes

In addition to DNA repair pathways, cells utilize translesion DNA synthesis (TLS) to bypass DNA lesions during replication. During TLS, Y-family DNA polymerase (Pol eta, Pol kappa, PolA +/- and Rev1) inserts specific nucleotide opposite preferred DNA lesions, and then Pol zeta consisting of two subunits, Rev3 and Rev7, carries out primer extension. Here, we report the complex structures of Rev3-Rev7-Rev1(CTD) and Rev3-Rev7-Rev1(CTD)-Pol kappa(RIR). These two structures demonstrate that Rev1(CTD) contains separate binding sites for Pol kappa and Rev7. Our BIAcore experiments provide additional support for the notion that the interaction between Rev3 and Rev7 increases the affinity of Rev7 and Rev1. We also verified through FRET experiment that Rev1, Rev3, Rev7 and Pol kappa form a stable quaternary complex in vivo, thereby suggesting an efficient switching mechanism where the inserter polymerase can be immediately replaced by an extender polymerase within the same quaternary complex.