Mechanism of human Lig1 regulation by PCNA in Okazaki fragment sealing.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 36539424.
- Also identified by DOI 10.1038/s41467-022-35475-z and PMC identifier 9767926.
- Licence recorded as CC BY.
- The licence permits redistribution, so the abstract is shown in full and the full text is available from the publisher.
Abstract
During lagging strand synthesis, DNA Ligase 1 (Lig1) cooperates with the sliding clamp PCNA to seal the nicks between Okazaki fragments generated by Pol δ and Flap endonuclease 1 (FEN1). We present several cryo-EM structures combined with functional assays, showing that human Lig1 recruits PCNA to nicked DNA using two PCNA-interacting motifs (PIPs) located at its disordered N-terminus (PIP<sub>N-term</sub>) and DNA binding domain (PIP<sub>DBD</sub>). Once Lig1 and PCNA assemble as two-stack rings encircling DNA, PIP<sub>N-term</sub> is released from PCNA and only PIP<sub>DBD</sub> is required for ligation to facilitate the substrate handoff from FEN1. Consistently, we observed that PCNA forms a defined complex with FEN1 and nicked DNA, and it recruits Lig1 to an unoccupied monomer creating a toolbelt that drives the transfer of DNA to Lig1. Collectively, our results provide a structural model on how PCNA regulates FEN1 and Lig1 during Okazaki fragments maturation.
Medical subject headings
- DNA Replication
- DNA Polymerase III