Cas9
核糖核酸
清脆的
反式激活crRNA
引导RNA
DNA
异源双工
计算生物学
核糖核蛋白
生物
遗传学
分子生物学
基因
作者
Gabriel Schuler,Chun-Yi Hu,Ailong Ke
出处
期刊:Science
[American Association for the Advancement of Science (AAAS)]
日期:2022-05-26
卷期号:376 (6600): 1476-1481
被引量:15
标识
DOI:10.1126/science.abq7220
摘要
Class 2 CRISPR effectors Cas9 and Cas12 may have evolved from nucleases in IS200/IS605 transposons. IscB is about two-fifths the size of Cas9 but shares a similar domain organization. The associated ωRNA plays the combined role of CRISPR RNA (crRNA) and trans-activating CRISPR RNA ( tracrRNA) to guide double-stranded DNA (dsDNA) cleavage. Here we report a 2.78-angstrom cryo–electron microscopy structure of IscB-ωRNA bound to a dsDNA target, revealing the architectural and mechanistic similarities between IscB and Cas9 ribonucleoproteins. Target-adjacent motif recognition, R-loop formation, and DNA cleavage mechanisms are explained at high resolution. ωRNA plays the equivalent function of REC domains in Cas9 and contacts the RNA-DNA heteroduplex. The IscB-specific PLMP domain is dispensable for RNA-guided DNA cleavage. The transition from ancestral IscB to Cas9 involved dwarfing the ωRNA and introducing protein domain replacements.
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