Recent advances in structural studies of the CRISPR-Cas-mediated genome editing tools

Clustered regularly interspaced short palindromic repeats (CRISPR) and accompanying CRISPR-associated (Cas) proteins provide RNA-guided adaptive immunity for prokaryotes to defend themselves against viruses. The CRISPR-Cas systems have attracted much attention in recent years for their power in aiding the development of genome editing tools. Based on the composition of the CRISPR RNA-effector complex, the CRISPR-Cas systems can be divided into two classes and six types. In this review, we summarize recent advances in the structural biology of the CRISPR-Cas-mediated genome editing tools, which helps us to understand the mechanism of how the guide RNAs assemble with diverse Cas proteins to cleave target nucleic acids.