| Structural highlights
Function
[RED1_HUMAN] Catalyzes the hydrolytic deamination of adenosine to inosine in double-stranded RNA (dsRNA) referred to as A-to-I RNA editing. This may affect gene expression and function in a number of ways that include mRNA translation by changing codons and hence the amino acid sequence of proteins; pre-mRNA splicing by altering splice site recognition sequences; RNA stability by changing sequences involved in nuclease recognition; genetic stability in the case of RNA virus genomes by changing sequences during viral RNA replication; and RNA structure-dependent activities such as microRNA production or targeting or protein-RNA interactions. Can edit both viral and cellular RNAs and can edit RNAs at multiple sites (hyper-editing) or at specific sites (site-specific editing). Its cellular RNA substrates include: bladder cancer-associated protein (BLCAP), neurotransmitter receptors for glutamate (GRIA2 and GRIK2) and serotonin (HTR2C), GABA receptor (GABRA3) and potassium voltage-gated channel (KCNA1). Site-specific RNA editing of transcripts encoding these proteins results in amino acid substitutions which consequently alter their functional activities. Edits GRIA2 at both the Q/R and R/G sites efficiently but converts the adenosine in hotspot1 much less efficiently. Can exert a proviral effect towards human immunodeficiency virus type 1 (HIV-1) and enhances its replication via both an editing-dependent and editing-independent mechanism. The former involves editing of adenosines in the 5'UTR while the latter occurs via suppression of EIF2AK2/PKR activation and function. Can inhibit cell proliferation and migration and can stimulate exocytosis.[1] [2] [3]
Publication Abstract from PubMed
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.
Structures of human ADAR2 bound to dsRNA reveal base-flipping mechanism and basis for site selectivity.,Matthews MM, Thomas JM, Zheng Y, Tran K, Phelps KJ, Scott AI, Havel J, Fisher AJ, Beal PA Nat Struct Mol Biol. 2016 May;23(5):426-33. doi: 10.1038/nsmb.3203. Epub 2016 Apr, 11. PMID:27065196[4]
From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine.
References
- ↑ Cenci C, Barzotti R, Galeano F, Corbelli S, Rota R, Massimi L, Di Rocco C, O'Connell MA, Gallo A. Down-regulation of RNA editing in pediatric astrocytomas: ADAR2 editing activity inhibits cell migration and proliferation. J Biol Chem. 2008 Mar 14;283(11):7251-60. doi: 10.1074/jbc.M708316200. Epub 2008 , Jan 4. PMID:18178553 doi:http://dx.doi.org/10.1074/jbc.M708316200
- ↑ Galeano F, Leroy A, Rossetti C, Gromova I, Gautier P, Keegan LP, Massimi L, Di Rocco C, O'Connell MA, Gallo A. Human BLCAP transcript: new editing events in normal and cancerous tissues. Int J Cancer. 2010 Jul 1;127(1):127-37. doi: 10.1002/ijc.25022. PMID:19908260 doi:10.1002/ijc.25022
- ↑ Doria M, Tomaselli S, Neri F, Ciafre SA, Farace MG, Michienzi A, Gallo A. ADAR2 editing enzyme is a novel human immunodeficiency virus-1 proviral factor. J Gen Virol. 2011 May;92(Pt 5):1228-32. doi: 10.1099/vir.0.028043-0. Epub 2011, Feb 2. PMID:21289159 doi:10.1099/vir.0.028043-0
- ↑ Matthews MM, Thomas JM, Zheng Y, Tran K, Phelps KJ, Scott AI, Havel J, Fisher AJ, Beal PA. Structures of human ADAR2 bound to dsRNA reveal base-flipping mechanism and basis for site selectivity. Nat Struct Mol Biol. 2016 May;23(5):426-33. doi: 10.1038/nsmb.3203. Epub 2016 Apr, 11. PMID:27065196 doi:http://dx.doi.org/10.1038/nsmb.3203
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