학술논문
Structures of human ADAR2 bound to dsRNA reveal base-flipping mechanism and basis for site selectivity
Document Type
Report
Author
Source
Nature Structural and Molecular Biology. May 1, 2016, p426, 10 p.
Subject
Language
English
ISSN
1545-9993
Abstract
RNA-editing reactions alter a transcript's genomically encoded sequence by inserting, deleting, or modifying nucleotides (1). Deamination of A, the most common form of RNA editing in humans, generates inosine (I) [...]
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.
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.