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Structure of the Saccharomyces cerevisiae replicative polymerase delta in complex with a primer/template and the PCNA clamp
Structural highlights
FunctionPCNA_YEAST This protein is an auxiliary protein of DNA polymerase delta and is involved in the control of eukaryotic DNA replication by increasing the polymerase's processibility during elongation of the leading strand. Involved in DNA repair.[1] [2] Publication Abstract from PubMedThe DNA polymerase (Pol) delta of Saccharomyces cerevisiae (S.c.) is composed of the catalytic subunit Pol3 along with two regulatory subunits, Pol31 and Pol32. Pol delta binds to proliferating cell nuclear antigen (PCNA) and functions in genome replication, repair, and recombination. Unique among DNA polymerases, the Pol3 catalytic subunit contains a 4Fe-4S cluster that may sense the cellular redox state. Here we report the 3.2-A cryo-EM structure of S.c. Pol delta in complex with primed DNA, an incoming ddTTP, and the PCNA clamp. Unexpectedly, Pol delta binds only one subunit of the PCNA trimer. This singular yet extensive interaction holds DNA such that the 2-nm-wide DNA threads through the center of the 3-nm interior channel of the clamp without directly contacting the protein. Thus, a water-mediated clamp and DNA interface enables the PCNA clamp to "waterskate" along the duplex with minimum drag. Pol31 and Pol32 are positioned off to the side of the catalytic Pol3-PCNA-DNA axis. We show here that Pol31-Pol32 binds single-stranded DNA that we propose underlies polymerase recycling during lagging strand synthesis, in analogy to Escherichia coli replicase. Interestingly, the 4Fe-4S cluster in the C-terminal CysB domain of Pol3 forms the central interface to Pol31-Pol32, and this strategic location may explain the regulation of the oxidation state on Pol delta activity, possibly useful during cellular oxidative stress. Importantly, human cancer and other disease mutations map to nearly every domain of Pol3, suggesting that all aspects of Pol delta replication are important to human health and disease. Structure of eukaryotic DNA polymerase delta bound to the PCNA clamp while encircling DNA.,Zheng F, Georgescu RE, Li H, O'Donnell ME Proc Natl Acad Sci U S A. 2020 Dec 1;117(48):30344-30353. doi: , 10.1073/pnas.2017637117. Epub 2020 Nov 17. PMID:33203675[3] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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