A bacterial Argonaute with noncanonical guide RNA specificity

作者：Kaya Emine; Doxzen Kevin W; Knoll Kilian R; Wilson Ross C; Strutt Steven C; Kranzusch Philip J; Doudna Jennifer A

来源：Proceedings of the National Academy of Sciences of the United States of America, 2016, 113(15): 4057-4062.

DOI：10.1073/pnas.1524385113

• Argonaute
• small noncoding RNA
• RNA interference

Eukaryotic Argonaute proteins induce gene silencing by small RNA-guided recognition and cleavage of mRNA targets. Although structural similarities between human and prokaryotic Argonautes are consistent with shared mechanistic properties, sequence and structure-based alignments suggested that Argonautes encoded within CRISPR-cas [clustered regularly interspaced short palindromic repeats (CRISPR)-associated] bacterial immunity operons have divergent activities. We show here that the CRISPR-associated Marinitoga piezophila Argonaute (MpAgo) protein cleaves single-stranded target sequences using 5'-hydroxylated guide RNAs rather than the 5'-phosphorylated guides used by all known Argonautes. The 2.0-angstrom resolution crystal structure of an MpAgo-RNA complex reveals a guide strand binding site comprising residues that block 5' phosphate interactions. Using structure-based sequence alignment, we were able to identify other putative MpAgo-like proteins, all of which are encoded within CRISPR-cas loci. Taken together, our data suggest the evolution of an Argonaute subclass with noncanonical specificity for a 5'-hydroxylated guide.

• 出版日期2016-4-12