Double-stranded RNA adenosine deaminase binds Z-DNA in vitro.
A Z-DNA binding protein of 140,000 M(r) has been purified from chicken lungs by sedimentation through 40%(w/w) sucrose and Z-DNA affinity chromatography. Specificity of the protein for Z-DNA was confirmed by competition with polyd(CG) that had been stabilized in the Z-DNA conformer by chemical bromination and also with a supercoiled plasmid that contains a Z-DNA-forming insert. In addition to a Z-DNA binding site, the protein also has a separate binding site for double-stranded RNA. Peptide sequence of the protein shows that it has high similarity to the RNA editing enzyme double-stranded RNA adenosine deaminase (dsRAD), which deaminates adenosine in dsRNA to form inosine. The Z-DNA binding protein has this enzymatic activity, confirming its identity to dsRAD. Recombinant human dsRAD also binds to Z-DNA. Z-DNA is stabilized in a sequence-dependent manner by negative supercoiling, which occurs in actively transcribed genes upstream to RNA polymerase. It is proposed that Z-DNA links editing to transcription by localizing dsRAD to a particular region of a gene and thus determines the efficiency with which an RNA is edited. The presence of Z-DNA forming elements in many genes raises the possibility that RNA editing by dsRAD is far more prevalent than is currently thought.
Herbert
A
A
Department of Biology, Massachusetts Institute of Technology, Cambridge 02178, USA.
Lowenhaupt
K
K
Spitzner
J
J
Rich
A
A
D000243:Adenosine Deaminase / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D002645:Chickens; D002846:Chromatography, Affinity; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry / Q000302:isolation & purification / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008970:Molecular Weight; D009690:Nucleic Acid Conformation; D017393:RNA Editing; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins / Q000378:metabolism; D012474:Salmon; D013379:Substrate Specificity; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D016601:RNA-Binding Proteins; D011994:Recombinant Proteins; D004247:DNA; C567955:ADARB1 protein, human; D000243:Adenosine Deaminase