Identification of fidelity-governing factors in human recombinases DMC1 and RAD51 from cryo-EM structures
Shih‐Chi Luo, Hsin‐Yi Yeh, Wei-Hsuan Lan, Yimin Wu, Cheng‐Han Yang, Hao-Yen Chang, Guan-Chin Su, Chia‐Yi Lee, Wen‐Jin Wu, Hung‐Wen Li, Meng‐Chiao Ho, Peter Chi, Ming‐Daw Tsai
Abstract
Both high-fidelity and mismatch-tolerant recombination, catalyzed by RAD51 and DMC1 recombinases, respectively, are indispensable for genomic integrity. Here, we use cryo-EM, MD simulation and functional analysis to elucidate the structural basis for the mismatch tolerance of DMC1. Structural analysis of DMC1 presynaptic and postsynaptic complexes suggested that the lineage-specific Loop 1 Gln244 (Met243 in RAD51) may help stabilize DNA backbone, whereas Loop 2 Pro274 and Gly275 (Val273/Asp274 in RAD51) may provide an open "triplet gate" for mismatch tolerance. In support, DMC1-Q244M displayed marked increase in DNA dynamics, leading to unobservable DNA map. MD simulation showed highly dispersive mismatched DNA ensemble in RAD51 but well-converged DNA in DMC1 and RAD51-V273P/D274G. Replacing Loop 1 or Loop 2 residues in DMC1 with RAD51 counterparts enhanced DMC1 fidelity, while reciprocal mutations in RAD51 attenuated its fidelity. Our results show that three Loop 1/Loop 2 residues jointly enact contrasting fidelities of DNA recombinases.