A Haloarchaeal Transcriptional Regulator That Represses the Expression of CRISPR-Associated Genes.

Clustered regularly interspaced short palindromic repeats (CRISPR)-Cas (CRISPR-associated proteins) systems provide acquired heritable protection to bacteria and archaea against selfish DNA elements, such as viruses. These systems must be tightly regulated because they can capture DNA fragments from foreign selfish elements, and also occasionally from self-chromosomes, resulting in autoimmunity. Most known species from the halophilic archaeal genus contain type I-B CRISPR-Cas systems, and the strongest hotspot for self-spacer acquisition by was a locus that contained a putative transposable element, as well as the gene , which was a very frequent target for self-targeting spacers.