title: A bacterial Argonaute with noncanonical guide RNA specificity.
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.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720; Physical Biosciences Division, Lawrence Berkeley National Laboratory, Berkeley, CA 94720;
authors.forename: Emine
authors.initials: E
authors.lastname: Kaya
authors.affiliation: Biophysics Graduate Group, University of California, Berkeley, CA 94720;
authors.forename: Kevin W
authors.initials: KW
authors.lastname: Doxzen
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720;
authors.forename: Kilian R
authors.initials: KR
authors.lastname: Knoll
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720;
authors.forename: Ross C
authors.initials: RC
authors.lastname: Wilson
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720;
authors.forename: Steven C
authors.initials: SC
authors.lastname: Strutt
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, CA 94720; Howard Hughes Medical Institute, University of California, Berkeley, CA 94720;
authors.forename: Philip J
authors.initials: PJ
authors.lastname: Kranzusch
authors.affiliation: 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.
authors.forename: Jennifer A
authors.initials: JA
authors.lastname: Doudna
mesh_terms: D060565:Argonaute Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001426:Bacterial Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D064112:Clustered Regularly Interspaced Short Palindromic Repeats; D005798:Genes, Bacterial; D008958:Models, Molecular; D000094704:RNA, Guide, CRISPR-Cas Systems / Q000378:metabolism*
chemical_list: D060565:Argonaute Proteins; D001426:Bacterial Proteins; D000094704:RNA, Guide, CRISPR-Cas Systems
keywords: Argonaute; RNA interference; small noncoding RNA