PURIFICATION OF HUMAN DOUBLE-STRANDED RNA-SPECIFIC EDITASE-1 (HRED1) INVOLVED IN EDITING OF BRAIN GLUTAMATE-RECEPTOR-B PRE-MESSENGER-RNA

RNAs encoding subunits of glutamate-gated ion channel receptors are po sttranscriptionally modified by RNA editing and alternative splicing. The change in amino acid sequence caused by RNA editing can affect bot h the kinetics and the permeability of the ion channel receptors to ca tions. Here, we report the purification of a 90-kDa double-stranded RN A-specific adenosine deaminase from HeLa cell nuclear extract that spe cifically edits the glutamine codon at position 586 in the pre-mRNA of the glutamate receptor B subunit. Site-specific deamination of an ade nosine to an inosine converts the glutamine codon to that of arginine. Recently, a gene encoding a double-stranded-specific editase (RED1) w as cloned from a rat brain cDNA library. Antibodies generated against the deaminase domain of its human homolog specifically recognized and inhibited the activity of the 90-kDa enzyme, indicating that we have p urified hRED1 the human homolog of rat RED1. This enzyme is distinct f rom double-stranded RNA-specific adenosine deaminase which we and othe rs have previously purified and cloned.