Eggers AR, Chen K, Soczek KM, Tuck OT, Doherty EE, Thornton BW, Xu B, Trinidad MI, Doudna JA. Rapid DNA unwinding accelerates genome editing by engineered CRISPR-Cas9.
BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.12.14.571777. [PMID:
38168238 PMCID:
PMC10760125 DOI:
10.1101/2023.12.14.571777]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/05/2024]
Abstract
Thermostable CRISPR-Cas9 enzymes could improve genome editing efficiency and delivery due to extended protein lifetimes. However, initial experimentation demonstrated Geobacillus stearothermophilus Cas9 (GeoCas9) to be virtually inactive when used in cultured human cells. Laboratory-evolved variants of GeoCas9 overcome this natural limitation by acquiring mutations in the wedge (WED) domain that produce >100-fold higher genome editing levels. Cryo-EM structures of the wildtype and improved GeoCas9 (iGeoCas9) enzymes reveal extended contacts between the WED domain of iGeoCas9 and DNA substrates. Biochemical analysis shows that iGeoCas9 accelerates DNA unwinding to capture substrates under the magnesium-restricted conditions typical of mammalian but not bacterial cells. These findings enabled rational engineering of other Cas9 orthologs to enhance genome editing levels, pointing to a general strategy for editing enzyme improvement. Together, these results uncover a new role for the Cas9 WED domain in DNA unwinding and demonstrate how accelerated target unwinding dramatically improves Cas9-induced genome editing activity.
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