Summary information and primary citation
- PDB-id
- 7qnz; SNAP-derived features in text and JSON formats;
DNAproDB
- Class
- replication
- Method
- cryo-EM (4.58 Å)
- Summary
- Human lig1-DNA-pcna complex reconstituted in absence of atp
- Reference
- Blair K, Tehseen M, Raducanu VS, Shahid T, Lancey C, Rashid F, Creuhet R, Hamdan SM, De Biasio A (2022): "Mechanism of human Lig1 regulation by PCNA in Okazaki fragment sealing." Nat Commun, 13, 7833. doi: 10.1038/s41467-022-35475-z.
- 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 (PIPN-term) and DNA binding domain (PIPDBD). Once Lig1 and PCNA assemble as two-stack rings encircling DNA, PIPN-term is released from PCNA and only PIPDBD 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.
