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Proc Natl Acad Sci U S A. 2016 Apr 12;113(15):4057-62. doi: 10.1073/pnas.1524385113. Epub 2016 Mar 30.

A bacterial Argonaute with noncanonical guide RNA specificity.

Author information

1
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
2
Biophysics Graduate Group, University of California, Berkeley, CA 94720;
3
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720;
4
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720; Howard Hughes Medical Institute, University of California, Berkeley, CA 94720;
5
Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720; Biophysics Graduate Group, University of California, Berkeley, CA 94720; Howard Hughes Medical Institute, University of California, Berkeley, CA 94720; Center for RNA Systems Biology, University of California, Berkeley, CA 94720; Innovative Genomics Initiative, University of California, Berkeley, CA 94720; Department of Chemistry, University of California, Berkeley, CA 94720 doudna@berkeley.edu.

Abstract

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-Å 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.

KEYWORDS:

Argonaute; RNA interference; small noncoding RNA

PMID:
27035975
PMCID:
PMC4839417
DOI:
10.1073/pnas.1524385113
[Indexed for MEDLINE]
Free PMC Article

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