Structural basis for cytosolic double-stranded RNA surveillance by human oligoadenylate synthetase 1.

TitleStructural basis for cytosolic double-stranded RNA surveillance by human oligoadenylate synthetase 1.
Publication TypeJournal Article
Year of Publication2013
AuthorsDonovan, J, Dufner, M, Korennykh, A
JournalProc Natl Acad Sci U S A
Volume110
Issue5
Pagination1652-7
Date Published2013 Jan 29
ISSN1091-6490
Keywords2',5'-Oligoadenylate Synthetase, Adenine Nucleotides, Amino Acid Sequence, Base Sequence, Binding Sites, Biocatalysis, Crystallography, X-Ray, Cytosol, Deoxyadenine Nucleotides, Enzyme Activation, Humans, Models, Molecular, Molecular Sequence Data, Nucleic Acid Conformation, Oligoribonucleotides, Protein Binding, Protein Structure, Tertiary, RNA, Double-Stranded, Sequence Homology, Amino Acid, Substrate Specificity
Abstract

<p>The human sensor of double-stranded RNA (dsRNA) oligoadenylate synthetase 1 (hOAS1) polymerizes ATP into 2',5'-linked iso-RNA (2-5A) involved in innate immunity, cell cycle, and differentiation. We report the crystal structure of hOAS1 in complex with dsRNA and 2'-deoxy ATP at 2.7 Å resolution, which reveals the mechanism of cytoplasmic dsRNA recognition and activation of oligoadenylate synthetases. Human OAS1 recognizes dsRNA using a previously uncharacterized protein/RNA interface that forms via a conformational change induced by binding of dsRNA. The protein/RNA interface involves two minor grooves and has no sequence-specific contacts, with the exception of a single hydrogen bond between the -NH(2) group of nucleobase G17 and the carbonyl oxygen of serine 56. Using a biochemical readout, we show that hOAS1 undergoes more than 20,000-fold activation upon dsRNA binding and that canonical or GU-wobble substitutions produce dsRNA mutants that retain either full or partial activity, in agreement with the crystal structure. Ultimately, the binding of dsRNA promotes an elaborate conformational rearrangement in the N-terminal lobe of hOAS1, which brings residues D75, D77, and D148 into proximity and creates coordination geometry for binding of two catalytic Mg(2+) ions and ATP. The assembly of this critical active-site structure provides the gate that couples binding of dsRNA to the production and downstream functions of 2-5A.</p>

DOI10.1073/pnas.1218528110
Alternate JournalProc. Natl. Acad. Sci. U.S.A.
PubMed ID23319625
PubMed Central IDPMC3562804