title: Structures of human ADAR2 bound to dsRNA reveal base-flipping mechanism and basis for site selectivity.
abstract: Adenosine deaminases acting on RNA (ADARs) are editing enzymes that convert adenosine to inosine in duplex RNA, a modification reaction with wide-ranging consequences in RNA function. Understanding of the ADAR reaction mechanism, the origin of editing-site selectivity, and the effect of mutations is limited by the lack of high-resolution structural data for complexes of ADARs bound to substrate RNAs. Here we describe four crystal structures of the human ADAR2 deaminase domain bound to RNA duplexes bearing a mimic of the deamination reaction intermediate. These structures, together with structure-guided mutagenesis and RNA-modification experiments, explain the basis of the ADAR deaminase domain's dsRNA specificity, its base-flipping mechanism, and its nearest-neighbor preferences. In addition, we identified an ADAR2-specific RNA-binding loop near the enzyme active site, thus rationalizing differences in selectivity observed between different ADARs. Finally, our results provide a structural framework for understanding the effects of ADAR mutations associated with human disease.
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Melissa M
authors.initials: MM
authors.lastname: Matthews
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Justin M
authors.initials: JM
authors.lastname: Thomas
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Yuxuan
authors.initials: Y
authors.lastname: Zheng
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Kiet
authors.initials: K
authors.lastname: Tran
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Kelly J
authors.initials: KJ
authors.lastname: Phelps
authors.affiliation: Department of Molecular and Cellular Biology, University of California, Davis, Davis, California, USA.
authors.forename: Anna I
authors.initials: AI
authors.lastname: Scott
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Jocelyn
authors.initials: J
authors.lastname: Havel
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.|Department of Molecular and Cellular Biology, University of California, Davis, Davis, California, USA.
authors.forename: Andrew J
authors.initials: AJ
authors.lastname: Fisher
authors.affiliation: Department of Chemistry, University of California, Davis, Davis, California, USA.
authors.forename: Peter A
authors.initials: PA
authors.lastname: Beal
mesh_terms: D000243:Adenosine Deaminase / Q000737:chemistry*; D001483:Base Sequence; D055162:Biocatalysis; D020134:Catalytic Domain; D018360:Crystallography, X-Ray; D006801:Humans; D006860:Hydrogen Bonding; D007700:Kinetics; D008958:Models, Molecular; D011485:Protein Binding; D012330:RNA, Double-Stranded / Q000737:chemistry*; D016601:RNA-Binding Proteins / Q000737:chemistry*; D013379:Substrate Specificity
chemical_list: D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase