TitleCas6 is an endoribonuclease that generates guide RNAs for invader defense in prokaryotes.
Publication TypeJournal Article
Year of Publication2008
AuthorsCarte J, Wang R, Li H, Terns RM, Terns MP
JournalGenes Dev
Date Published2008 Dec 15
KeywordsEscherichia coli, Genes, Bacterial, Models, Molecular, Prokaryotic Cells, Protein Structure, Tertiary, Pyrococcus furiosus, Repetitive Sequences, Nucleic Acid, RNA, Bacterial, RNA, Guide
AbstractAn RNA-based gene silencing pathway that protects bacteria and archaea from viruses and other genome invaders is hypothesized to arise from guide RNAs encoded by CRISPR loci and proteins encoded by the cas genes. CRISPR loci contain multiple short invader-derived sequences separated by short repeats. The presence of virus-specific sequences within CRISPR loci of prokaryotic genomes confers resistance against corresponding viruses. The CRISPR loci are transcribed as long RNAs that must be processed to smaller guide RNAs. Here we identified Pyrococcus furiosus Cas6 as a novel endoribonuclease that cleaves CRISPR RNAs within the repeat sequences to release individual invader targeting RNAs. Cas6 interacts with a specific sequence motif in the 5' region of the CRISPR repeat element and cleaves at a defined site within the 3' region of the repeat. The 1.8 angstrom crystal structure of the enzyme reveals two ferredoxin-like folds that are also found in other RNA-binding proteins. The predicted active site of the enzyme is similar to that of tRNA splicing endonucleases, and concordantly, Cas6 activity is metal-independent. cas6 is one of the most widely distributed CRISPR-associated genes. Our findings indicate that Cas6 functions in the generation of CRISPR-derived guide RNAs in numerous bacteria and archaea.
Alternate JournalGenes Dev.
PubMed ID19141480