7tib
Structure of the yeast clamp loader (Replication Factor C RFC) bound to the open sliding clamp (Proliferating Cell Nuclear Antigen PCNA) and primer-template DNA
Structural highlights
FunctionRFC4_YEAST Component of ATP-dependent clamp loader (RFC and RFC-like) complexes for DNA clamps, such as the POL30/PCNA homotrimer and the checkpoint clamp DDC1:MEC3:RAD17 complex. During a clamp loading circle, the RFC:clamp complex binds to DNA and the recognition of the double-stranded/single-stranded junction stimulates ATP hydrolysis by RFC. The complex presumably provides bipartite ATP sites in which one subunit supplies a catalytic site for hydrolysis of ATP bound to the neighboring subunit. Dissociation of RFC from the clamp leaves the clamp encircling DNA. Component of the replication factor C (RFC or activator 1) complex which loads POL30/PCNA and acts during elongation of primed DNA templates by DNA polymerase delta and epsilon. RFC has an essential but redundant activity in sister chromatid cohesion establishment. Component of the RFC-like complex CTF18-RFC which is required for efficient establishment of chromosome cohesion during S-phase and may load or unload POL30/PCNA. Component of the RFC-like RAD24-RFC complex which loads the checkpoint clamp DDC1:MEC3:RAD17 complex and is involved in DNA repair pathways. Component of the RFC-like ELG1-RFC complex which appears to have a role in DNA replication, replication fork re-start, recombination and repair.[1] [2] [3] Publication Abstract from PubMedSliding clamps are ring-shaped protein complexes that are integral to the DNA replication machinery of all life. Sliding clamps are opened and installed onto DNA by clamp loader AAA+ ATPase complexes. However, how a clamp loader opens and closes the sliding clamp around DNA is still unknown. Here, we describe structures of the Saccharomyces cerevisiae clamp loader Replication Factor C (RFC) bound to its cognate sliding clamp Proliferating Cell Nuclear Antigen (PCNA) en route to successful loading. RFC first binds to PCNA in a dynamic, closed conformation that blocks both ATPase activity and DNA binding. RFC then opens the PCNA ring through a large-scale 'crab-claw' expansion of both RFC and PCNA that explains how RFC prefers initial binding of PCNA over DNA. Next, the open RFC:PCNA complex binds DNA and interrogates the primer-template junction using a surprising base-flipping mechanism. Our structures indicate that initial PCNA opening and subsequent closure around DNA do not require ATP hydrolysis, but are driven by binding energy. ATP hydrolysis, which is necessary for RFC release, is triggered by interactions with both PCNA and DNA, explaining RFC's switch-like ATPase activity. Our work reveals how a AAA+ machine undergoes dramatic conformational changes for achieving binding preference and substrate remodeling. Cryo-EM structures reveal high-resolution mechanism of a DNA polymerase sliding clamp loader.,Gaubitz C, Liu X, Pajak J, Stone NP, Hayes JA, Demo G, Kelch BA Elife. 2022 Feb 18;11:e74175. doi: 10.7554/eLife.74175. PMID:35179493[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. See AlsoReferences
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