May 12, 2015

Co-transcriptional DNA and RNA Cleavage during Type III CRISPR-Cas Immunity

Cell
Poulami SamaiLuciano A Marraffini

Abstract

Immune systems must recognize and destroy different pathogens that threaten the host. CRISPR-Cas immune systems protect prokaryotes from viral and plasmid infection utilizing small CRISPR RNAs that are complementary to the invader's genome and specify the targets of RNA-guided Cas nucleases. Type III CRISPR-Cas immunity requires target transcription, and whereas genetic studies demonstrated DNA targeting, in vitro data have shown crRNA-guided RNA cleavage. The molecular mechanism behind these disparate activities is not known. Here, we show that transcription across the targets of the Staphylococcus epidermidis type III-A CRISPR-Cas system results in the cleavage of the target DNA and its transcripts, mediated by independent active sites within the Cas10-Csm ribonucleoprotein effector complex. Immunity against plasmids and DNA viruses requires DNA, but not RNA, cleavage activity. Our studies reveal a highly versatile mechanism of CRISPR immunity that can defend microorganisms against diverse DNA and RNA invaders.

Mentioned in this Paper

Symphurus thermophilus
Tetracycline Antibiotics
Study
Biochemical Pathway
Immune System
Ethanol
CBR 703
Polymerase
Erythromycin
Derivatives

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