8fs3
From Proteopedia
Structure of S. cerevisiae Rad24-RFC loading the 9-1-1 clamp onto a 10-nt gapped DNA in step 1 (open 9-1-1 and shoulder bound DNA only)
Structural highlights
FunctionRAD24_YEAST Participates in checkpoint pathways arrest of the cell cycle, a mechanism that allows the DNA repair pathways to act to restore the integrity of the DNA prior to DNA synthesis or separation of the replicated chromosomes. Regulates the DNA damage checkpoint pathway throughout the cell cycle, when associated with RCF5. Component of the RFC-like RAD24-RFC complex which loads the checkpoint clamp DDC1:MEC3:RAD17 complex and is involved in DNA repair pathways. 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.[1] [2] [3] Publication Abstract from PubMedRecent structural studies show the Rad24-RFC loads the 9-1-1 checkpoint clamp onto a recessed 5' end by binding the 5' DNA on Rad24 at an external surface site and threading the 3' ssDNA into the well-established internal chamber and into 9-1-1. We find here that Rad24-RFC loads 9-1-1 onto DNA gaps in preference to a recessed 5' DNA end, thus presumably leaving 9-1-1 on a 3' ss/ds DNA after Rad24-RFC ejects from the 5' gap end and may explain reports of 9-1-1 directly functioning in DNA repair with various TLS polymerases, in addition to signaling the ATR kinase. To gain a deeper understanding of 9-1-1 loading at gaps we report high-resolution structures of Rad24-RFC during loading of 9-1-1 onto 10-nt and 5-nt gapped DNAs. At a 10-nt gap we captured five Rad24-RFC-9-1-1 loading intermediates in which the 9-1-1 DNA entry gate varies from fully open to fully closed around DNA using ATPgammaS, supporting the emerging view that ATP hydrolysis is not needed for clamp opening/closing, but instead for dissociation of the loader from the clamp encircling DNA. The structure of Rad24-RFC-9-1-1 at a 5-nt gap shows a 180 degrees axially rotated 3'-dsDNA which orients the template strand to bridge the 3'- and 5'- junctions with a minimum 5-nt ssDNA. The structures reveal a unique loop on Rad24 that limits the length of dsDNA in the inner chamber, and inability to melt DNA ends unlike RFC, thereby explaining Rad24-RFC's preference for a preexisting ssDNA gap and suggesting a direct role in gap repair in addition to its checkpoint role. Structures of 9-1-1 DNA checkpoint clamp loading at gaps from start to finish and ramification to biology.,Zheng F, Georgescu RE, Yao NY, O'Donnell ME, Li H bioRxiv. 2023 May 3:2023.05.03.539266. doi: 10.1101/2023.05.03.539266. Preprint. PMID:37205533[4] From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine. References
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