Interaction with PCNA is essential for yeast DNA polymerase η function

In both yeast and humans, DNA polymerase (Pol) η functions in error-free replication of ultraviolet-damaged DNA, and Polη promotes replication through many other DNA lesions as well. Here, we present evidence for the physical and functional interaction of yeast Polη with proliferating cell nuclear antigen (PCNA) and show that the interaction with PCNA is essential for the in vivo function of Polη. Polη is highly inefficient at inserting a nucleotide opposite an abasic site, but interaction with PCNA greatly stimulates its ability for nucleotide incorporation opposite this lesion. Thus, in addition to having a pivotal role in the targeting of Polη to the replication machinery stalled at DNA lesions, interaction with PCNA would promote the bypass of certain DNA lesions.