Casposons: mobile genetic elements that gave rise to the CRISPR-Cas adaptation machinery. (August 2017)

• Record Type: Journal Article
• Authors: Krupovic, Mart; Béguin, Pierre; Koonin, Eugene V
• Is Part Of: Current opinion in microbiology. Volume 38(2017)
• Page Start: 36
• Page End: 43
• Publication Date: 2017-08
• Subjects: Microbiology -- Periodicals; 579.05
• DOI: 10.1016/j.mib.2017.04.004
• Languages: English
• ISSNs: 1369-5274

Abstract

Graphical abstract: Highlights: Casposons are self-replicating mobile genetic elements found in bacteria and archaea. Casposase is an active casposon integrase homologous to CRISPR-Cas1. Casposons gave rise to the adaptation machinery of CRISPR-Cas. CRISPR repeats and the Leader sequence have evolved from the casposon target site. Recruitment of Cas2 was crucial for transforming the casposase into Cas1. Abstract : A casposon, a member of a distinct superfamily of archaeal and bacterial self-synthesizing transposons that employ a recombinase (casposase) homologous to the Cas1 endonuclease, appears to have given rise to the adaptation module of CRISPR-Cas systems as well as the CRISPR repeats themselves. Comparison of the mechanistic features of the reactions catalyzed by the casposase and the Cas1–Cas2 heterohexamer, the CRISPR integrase, reveals close similarity but also important differences that explain the requirement of Cas2 for integration of short DNA fragments, the CRISPR spacers.