CRISPR–Cas systems provide resistance against foreign mobile genetic elements and have
a wide range of genome editing and biotechnological applications. In this Review, we …

The number and diversity of known CRISPR–Cas systems have substantially increased in
recent years. Here, we provide an updated evolutionary classification of CRISPR–Cas …

IscB proteins are putative nucleases encoded in a distinct family of IS200/IS605 transposons
and are likely ancestors of the RNA-guided endonuclease Cas9, but the functions of IscB …

INTRODUCTION Bacteria and archaea are frequently attacked by viruses (phages) and as a
result have developed multiple, sophisticated lines of active defense that can collectively be …

Highlights•Two classes of CRISPR-Cas systems differ by the architectures of effector
modules.•Effectors of Class 2 CRISPR-Cas systems are large, multidomain proteins.•Effector …

CRISPR-Cas, the bacterial and archaeal adaptive immunity systems, encompass a complex
machinery that integrates fragments of foreign nucleic acids, mostly from mobile genetic …

Clustered regularly interspaced short palindromic repeat (CRISPR)-Cas systems are well-
known acquired immunity systems that are widespread in archaea and bacteria. The RNA …

The evolution of CRISPR–cas loci, which encode adaptive immune systems in archaea and
bacteria, involves rapid changes, in particular numerous rearrangements of the locus …

Insertion sequences are compact and pervasive transposable elements found in bacteria,
which encode only the genes necessary for their mobilization and maintenance. IS200-and …

Microbial CRISPR-Cas systems are divided into Class 1, with multisubunit effector
complexes, and Class 2, with single protein effectors. Currently, only two Class 2 effectors …