Download MendeleyStructures of LIG1 that engage with mutagenic mismatches inserted by pol beta in base excision repair.
Tang, Q., Gulkis, M., McKenna, R., Caglayan, M.(2022) Nat Commun 13: 3860-3860
- PubMed: 35790757
- DOI: https://doi.org/10.1038/s41467-022-31585-w
- Primary Citation of Related Structures:
7SUM, 7SX5, 7SXE - PubMed Abstract:
DNA ligase I (LIG1) catalyzes the ligation of the nick repair intermediate after gap filling by DNA polymerase (pol) β during downstream steps of the base excision repair (BER) pathway. However, how LIG1 discriminates against the mutagenic 3'-mismatches incorporated by polβ at atomic resolution remains undefined. Here, we determine the X-ray structures of LIG1/nick DNA complexes with G:T and A:C mismatches and uncover the ligase strategies that favor or deter the ligation of base substitution errors. Our structures reveal that the LIG1 active site can accommodate a G:T mismatch in the wobble conformation, where an adenylate (AMP) is transferred to the 5'-phosphate of a nick (DNA-AMP), while it stays in the LIG1-AMP intermediate during the initial step of the ligation reaction in the presence of an A:C mismatch at the 3'-strand. Moreover, we show mutagenic ligation and aberrant nick sealing of dG:T and dA:C mismatches, respectively. Finally, we demonstrate that AP-endonuclease 1 (APE1), as a compensatory proofreading enzyme, removes the mismatched bases and interacts with LIG1 at the final BER steps. Our overall findings provide the features of accurate versus mutagenic outcomes coordinated by a multiprotein complex including polβ, LIG1, and APE1 to maintain efficient repair.
Organizational Affiliation:
Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, 32610, USA.
