Fig. 5: Cryo-EM structures of FEN1–DNA–PCNA and Lig1–DNA–PCNA–FEN1 complexes.

a Cryo-EM density map of the FEN1–DNA–PCNA complex colored by domains. b Three views of the cryo-EM density map of the FEN1–DNA–PCNA complex with fitted model. c Two views of the cryo-EM density map of the Lig1–DNA–PCNA–FEN1 complex colored by domains. d Model of the complex in ribbon representation fitted into the cryo-EM map, and colored by component. The structure represents a step of the Okazaki fragment maturation reaction following handover of the nicked DNA substrate from FEN1 to Lig1 to complete nick sealing. e Details of the model at the FEN1–OBD interface. The cryo-EM map around FEN1 is shown, indicating that only the FEN1 central core is well ordered. f Possible steps for the mechanism of handoff of nicked DNA from FEN1 to Lig1. The model in the central panel shows Lig1 in the “open conformation”, where the OBD is flexible and extending away from the AdD (Supplementary Fig. 7).