Principal Investigator Graham Walker
Humans have four Y Family translesion DNA polymerases including the Xeroderma pigmentosum variant gene product (pol eta), which can copy accurately over cyclobutane thymine-thymine dimers. S. cerevisiae has two, pol eta and Rev1, while S. pombe additionally encodes a dinB ortholog (pol kappa). Various observations suggest that, like UmuC and DinB, the action of these DNA polymerases is controlled by a complex set of protein-protein interactions and we have initiated an effort to understand the molecular basis of the control of these proteins in yeast and humans. We recently discovered that S. cerevisiae Rev1 (required for UV and chemical mutagenesis in all eukaryotes) is dramatically cell-cycle regulated (50 fold higher in G2/M than in G1 and S). This observation suggests that mutagenic TLS occurs at gaps left behind after DNA replication rather than at the replication fork itself.
Although Rev1’s capacity as a DNA polymerase is limited to inserting dC’s, it plays a critical role by recruiting other translesion DNA polymerases including pol zeta (Rev3/Rev7). We have identified novel and hitherto unrecognized conserved motifs that play an essential role in REV1-dependent mutagenesis in S. cerevisiae and have shown that a minimal C-terminal fragment of Rev1 containing these highly conserved motifs is sufficient to interact with Rev7.
On-going projects include investigating the molecular basis of Rev1 cell-cycle control; extending our studies of Rev1 function to mammals in collaboration with Michael Hemann; exploring the UBZ ubiquitin-binding domain of S. cerevisiae pol eta; and analyzing the function and control of the S. pombe dinB ortholog.