High-throughput determination of in vivo DNA sequence preferences for Cas protein binding using Library-ChIP.

The specificity of CRISPR-Cas systems for nucleic acid targets is determined by a combination of binding and cleavage. Understanding the mechanisms by which Cas proteins specifically select their targets is critical for the development of CRISPR-Cas systems for biotechnology applications. Moreover, the specificity of CRISPR-Cas systems plays an important role in prokaryote evolution due to its role in distinguishing self from nonself. Here, I describe Library-ChIP, a high-throughput method for measuring Cas protein occupancy at many DNA sequence variants in a native prokaryotic host. Library-ChIP can be used to identify the determinants of specificity for Cas protein binding to nucleic acid targets.