Summary information and primary citation

PDB-id
7sgz; SNAP-derived features in text and JSON formats; DNAproDB
Class
DNA binding protein-DNA
Method
cryo-EM (3.17 Å)
Summary
Structure of the yeast rad24-rfc loader bound to DNA and the closed 9-1-1 clamp
Reference
Zheng F, Georgescu RE, Yao NY, O'Donnell ME, Li H (2022): "DNA is loaded through the 9-1-1 DNA checkpoint clamp in the opposite direction of the PCNA clamp." Nat.Struct.Mol.Biol., 29, 376-385. doi: 10.1038/s41594-022-00742-6.
Abstract
The 9-1-1 DNA checkpoint clamp is loaded onto 5'-recessed DNA to activate the DNA damage checkpoint that arrests the cell cycle. The 9-1-1 clamp is a heterotrimeric ring that is loaded in Saccharomyces cerevisiae by Rad24-RFC (hRAD17-RFC), an alternate clamp loader in which Rad24 replaces Rfc1 in the RFC1-5 clamp loader of proliferating cell nuclear antigen (PCNA). The 9-1-1 clamp loading mechanism has been a mystery, because, unlike RFC, which loads PCNA onto a 3'-recessed junction, Rad24-RFC loads the 9-1-1 ring onto a 5'-recessed DNA junction. Here we report two cryo-EM structures of Rad24-RFC-DNA with a closed or 27-Å open 9-1-1 clamp. The structures reveal a completely unexpected mechanism by which a clamp can be loaded onto DNA. Unlike RFC, which encircles DNA, Rad24 binds 5'-DNA on its surface, not inside the loader, and threads the 3' ssDNA overhang into the 9-1-1 clamp from above the ring.

Cartoon-block schematics in six views (download the tarball)

PyMOL session file Download PDB file View in 3Dmol.js