文章基本信息

标题：High-throughput biochemical profiling reveals sequence determinants of dCas9 off-target binding and unbinding
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作者：Evan A. Boyle ; Johan O. L. Andreasson ; Lauren M. Chircus 等
期刊名称：Proceedings of the National Academy of Sciences
印刷版ISSN：0027-8424
电子版ISSN：1091-6490
出版年度：2017
卷号：114
期号：21
页码：5461-5466
DOI：10.1073/pnas.1700557114
语种：English
出版社：The National Academy of Sciences of the United States of America
摘要：The bacterial adaptive immune system CRISPR–Cas9 has been appropriated as a versatile tool for editing genomes, controlling gene expression, and visualizing genetic loci. To analyze Cas9’s ability to bind DNA rapidly and specifically, we generated multiple libraries of potential binding partners for measuring the kinetics of nuclease-dead Cas9 (dCas9) interactions. Using a massively parallel method to quantify protein–DNA interactions on a high-throughput sequencing flow cell, we comprehensively assess the effects of combinatorial mismatches between guide RNA (gRNA) and target nucleotides, both in the seed and in more distal nucleotides, plus disruption of the protospacer adjacent motif (PAM). We report two consequences of PAM-distal mismatches: reversal of dCas9 binding at long time scales, and synergistic changes in association kinetics when other gRNA–target mismatches are present. Together, these observations support a model for Cas9 specificity wherein gRNA–DNA mismatches at PAM-distal bases modulate different biophysical parameters that determine association and dissociation rates. The methods we present decouple aspects of kinetic and thermodynamic properties of the Cas9–DNA interaction and broaden the toolkit for investigating off-target binding behavior.
关键词：DNA ; molecular biophysics ; kinetics ; sequencing ; CRISPR