PURIFICATION AND CHARACTERIZATION OF A HUMAN RNA ADENOSINE-DEAMINASE FOR GLUTAMATE-RECEPTOR-B PRE-MESSENGER-RNA EDITING

The glutamate receptor subunit R (GluR-B) pre-mRNA is edited at two ad enosine residues, resulting in amino acid changes that alter the elect rophysiologic properties of a-he glutamate receptor, Previous studies showed that these amino acid changes are due to adenosine to inosine c onversions in two codons resulting from adenosine deamination, Here, w e describe the purification and characterization of an activity from h uman HeLa cells that efficiently and accurately edits GluR-B pre-mRNA at both of these sites, The purified activity contains a human homolog of the recently reported rat RED1 (rRED1) protein, a member of the fa mily of double-stranded RNA-dependent deaminase proteins, Recombinant human RED1 (hRED1), but not recombinant dsRAD, another member of the f amily, efficiently edits both the Q/R and R/G sites of GluR-B RNA. We conclude that the GluR-B editing activity present in Beta cell extract s and the recombinant hRED1 protein are indistinguishable.