title: ADAR1 RNA deaminase limits short interfering RNA efficacy in mammalian cells.
abstract: Double-stranded RNA induces the homology-dependent degradation of cognate mRNA in the cytoplasm via RNA interference (RNAi) but also is a target for adenosine-to-inosine (A-to-I) RNA editing by adenosine deaminases acting on RNA (ADARs). An interaction between the RNAi and the RNA editing pathways in Caenorhabditis elegans has been suggested recently, but the precise mode of interaction remains to be established. In addition, it is unclear whether this interaction is possible in mammalian cells with their somewhat different RNAi pathways. Here we show that ADAR1 and ADAR2, but not ADAR3, avidly bind short interfering RNA (siRNA) without RNA editing. In particular, the cytoplasmic full-length isoform of ADAR1 has the highest affinity among known ADARs, with a subnanomolar dissociation constant. Gene silencing by siRNA is significantly more effective in mouse fibroblasts homozygous for an ADAR1 null mutation than in wild-type cells. In addition, suppression of RNAi effects are detected in fibroblast cells overexpressing functional ADAR1 but not when overexpressing mutant ADAR1 lacking double-stranded RNA-binding domains. These results identify ADAR1 as a cellular factor that limits the efficacy of siRNA in mammalian cells.
authors.affiliation: The Wistar Institute, Philadelphia, Pennsylvania 19104, USA.
authors.forename: Weidong
authors.initials: W
authors.lastname: Yang
authors.forename: Qingde
authors.initials: Q
authors.lastname: Wang
authors.forename: Kelly L
authors.initials: KL
authors.lastname: Howell
authors.forename: Joshua T
authors.initials: JT
authors.lastname: Lee
authors.forename: Dan-Sung C
authors.initials: DS
authors.lastname: Cho
authors.forename: John M
authors.initials: JM
authors.lastname: Murray
authors.forename: Kazuko
authors.initials: K
authors.lastname: Nishikura
mesh_terms: D000243:Adenosine Deaminase / Q000235:genetics* / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured; D005347:Fibroblasts / Q000166:cytology; D015870:Gene Expression; D020868:Gene Silencing / Q000502:physiology; D008322:Mammals; D051379:Mice; D011485:Protein Binding / Q000235:genetics; D017393:RNA Editing / Q000502:physiology; D034741:RNA, Small Interfering / Q000378:metabolism*; D016601:RNA-Binding Proteins
chemical_list: D034741:RNA, Small Interfering; D016601:RNA-Binding Proteins; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase