CRISPR (clustered regularly interspaced short palindromic repeat) is an adaptive immune system that provides protection against mobile genetic elements (viruses, transposable elements and conjugative plasmids). CRISPR clusters contain spacers, sequences complementary to antecedent mobile elements, and target invading nucleic acids. CRISPR clusters are transcribed and processed into CRISPR RNA (crRNA) (By similarity). Can form a Cascade complex with Cas7, Cas5a, Cas3, Cas3' and Cas8a2. Repressed by 5 J/m2 ultraviolet light and 50 mM NaCl, slightly induced by 20 J/m2 ultraviolet light, 100 and 150 mM Nacl. Member of the csa5-cas7-cas5a-cas3-cas3'-cas8a2 operon.