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). The CMR complex degrades RNA complementary to the crRNA (target RNA) within UA dinucleotides, generating 3'-OH and 5'-phosphate ends. Activity is dependent on the 8 nt long 5' tag in the crRNA, an unpaired 3' flag on the target RNA, and is stimulated by ATP. Some cleavage of the guide crRNA can also be observed. Part of the CMR ribonucleoprotein complex, consisting of crRNA plus Cmr1/Cmr2/Cmr3/Cmr4/Cmr5/Cmr6 at 1:1 and possibly 3 Cmr7 dimers. A Cmr2/Cmr3/Cmr7 subcomplex without crRNA can also be isolated. It does not cleave target RNA. Belongs to the CRISPR system Cmr6 family.