Mechanism of PCNA loading by Ctf18-RFC for leading-strand DNA synthesis

• 成果类型: Article
• 署名作者: Yuan, Zuanning; Georgescu, Roxana; Yao, Nina Y.; Yurieva, Olga; O'Donnell, Michael E.; Li, Huilin
• 署名单位: Van Andel Institute; Rockefeller University; Howard Hughes Medical Institute
• 刊物名称: SCIENCE
• ISSN/ISSBN: 0036-9581
• DOI: 10.1126/science.adk5901
• 发表日期: 2024-08-02
• 关键词: cell nuclear antigen; sister-chromatid cohesion; replication factor-c; polymerase-delta; auxiliary protein; structural basis; mismatch repair; epsilon form; clamp; complex

摘要

The proliferating cell nuclear antigen (PCNA) clamp encircles DNA to hold DNA polymerases (Pols) to DNA for processivity. The Ctf18-RFC PCNA loader, a replication factor C (RFC) variant, is specific to the leading-strand Pol (Pol epsilon). We reveal here the underlying mechanism of Ctf18-RFC specificity to Pol epsilon using cryo-electron microscopy and biochemical studies. We found that both Ctf18-RFC and Pol epsilon contain specific structural features that direct PCNA loading onto DNA. Unlike other clamp loaders, Ctf18-RFC has a disordered ATPase associated with a diverse cellular activities (AAA+) motor that requires Pol epsilon to bind and stabilize it for efficient PCNA loading. In addition, Ctf18-RFC can pry prebound Pol epsilon off of DNA, then load PCNA onto DNA and transfer the PCNA-DNA back to Pol epsilon. These elements in both Ctf18-RFC and Pol epsilon provide specificity in loading PCNA onto DNA for Pol epsilon.