Distinct in vivo roles for double-stranded RNA-binding domains of the Xenopus RNA-editing enzyme ADAR1 in chromosomal targeting.
The RNA-editing enzyme adenosine deaminase that acts on RNA (ADAR1) deaminates adenosines to inosines in double-stranded RNA substrates. Currently, it is not clear how the enzyme targets and discriminates different substrates in vivo. However, it has been shown that the deaminase domain plays an important role in distinguishing various adenosines within a given substrate RNA in vitro. Previously, we could show that Xenopus ADAR1 is associated with nascent transcripts on transcriptionally active lampbrush chromosomes, indicating that initial substrate binding and possibly editing itself occurs cotranscriptionally. Here, we demonstrate that chromosomal association depends solely on the three double-stranded RNA-binding domains (dsRBDs) found in the central part of ADAR1, but not on the Z-DNA-binding domain in the NH2 terminus nor the catalytic deaminase domain in the COOH terminus of the protein. Most importantly, we show that individual dsRBDs are capable of recognizing different chromosomal sites in an apparently specific manner. Thus, our results not only prove the requirement of dsRBDs for chromosomal targeting, but also show that individual dsRBDs have distinct in vivo localization capabilities that may be important for initial substrate recognition and subsequent editing specificity.
Doyle
Michael
M
Dept. of Cell Biology and Genetics, Institute of Botany, University of Vienna, Rennweg 14, A-1030 Vienna, Austria.
Jantsch
Michael F
MF
D000243:Adenosine Deaminase / Q000235:genetics* / Q000378:metabolism; D000818:Animals; D020134:Catalytic Domain / Q000235:genetics; D002467:Cell Nucleus / Q000201:enzymology* / Q000235:genetics; D002875:Chromosomes / Q000235:genetics*; D005057:Eukaryotic Cells / Q000166:cytology / Q000201:enzymology*; D005260:Female; D005809:Genes, Regulator / Q000235:genetics; D009865:Oocytes; D017434:Protein Structure, Tertiary / Q000235:genetics; D017393:RNA Editing / Q000235:genetics*; D012330:RNA, Double-Stranded / Q000235:genetics* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D014982:Xenopus laevis
D012330:RNA, Double-Stranded; D016601:RNA-Binding Proteins; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase