title: Structural basis for cytosolic double-stranded RNA surveillance by human oligoadenylate synthetase 1.
abstract: 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.
authors: Department of Molecular Biology, Princeton University, Princeton, NJ 08540, USA.
authors: Jesse
authors: J
authors: Donovan
authors: Matthew
authors: M
authors: Dufner
authors: Alexei
authors: A
authors: Korennykh
mesh_terms: D015088:2',5'-Oligoadenylate Synthetase / Q000737:chemistry* / Q000378:metabolism; D000227:Adenine Nucleotides / Q000737:chemistry / Q000378:metabolism; D000595:Amino Acid Sequence; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D055162:Biocatalysis; D018360:Crystallography, X-Ray; D003600:Cytosol / Q000378:metabolism; D003838:Deoxyadenine Nucleotides / Q000737:chemistry / Q000378:metabolism; D004789:Enzyme Activation; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D009843:Oligoribonucleotides / Q000737:chemistry / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012330:RNA, Double-Stranded / Q000737:chemistry* / Q000378:metabolism; D017386:Sequence Homology, Amino Acid; D013379:Substrate Specificity
chemical_list: D000227:Adenine Nucleotides; D003838:Deoxyadenine Nucleotides; D009843:Oligoribonucleotides; D012330:RNA, Double-Stranded; C023505:2',5'-oligoadenylate; C475085:OAS1 protein, human; D015088:2',5'-Oligoadenylate Synthetase; C026600:2'-deoxyadenosine triphosphate