Editing of α-Amino-3-hydroxy-5-methylisoxazole-4-propionic Acid Receptor GluR-B Pre-mRNA in Vitro Reveals Site-selective Adenosine to Inosine Conversion

In neurons of the mammalian brain primary transcripts of genes encoding subunits of glutamate receptor channels can undergo RNA editing, leading to altered properties of the transmitter-activated channel. Editing of these transcripts is a nuclear process that targets specific adenosines and requires a double-stranded RNA structure configured from complementary exonic and intronic sequences. We show here that the two independent editing sites in alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid receptor GluR-B pre-mRNA are edited with positional accuracy by nuclear extract from HeLa cells. Nucleotide analysis by thin layer chromatography of the edited RNA sequences revealed selective adenosine to inosine conversion, most likely reflecting the participation of double-stranded RNA adenosine deaminase. Our results predict the presence of inosine-containing codons in other mammalian mRNAs.