MOLECULAR-CLONING OF CDNA FOR DOUBLE-STRANDED-RNA ADENOSINE-DEAMINASE, A CANDIDATE ENZYME FOR NUCLEAR-RNA EDITING

We have cloned human cDNA encoding double-stranded RNA adenosine deami nase (DRADA). DRADA is a ubiquitous nuclear enzyme that converts multi ple adenosines to inosines in double helical RNA substrates without ap parent sequence specificity. The A --> I conversion activity of the pr otein encoded by the cloned cDNA was confirmed by recombinant expressi on in insect cells. Use of the cloned DNA as a molecular probe documen ted sequence conservation across mammals and detected a single transcr ipt of 7 kb in RNA of all human tissues analyzed. The deduced primary structure of human DRADA revealed a bipartite nuclear localization sig nal, three repeats of a double-stranded RNA binding moth, and the pres ence of sequences conserved in the catalytic center of other deaminase s, including a cytidine deaminase involved in the RNA editing of apoli poprotein B. These structural properties are consistent with the enzym atic signature of DRADA, and strengthen the hypothesis that DRADA carr ies out the RNA editing of transcripts encoding glutamate gated ion ch annels in brain.