EDITING OF GLUTAMATE-RECEPTOR SUBUNIT-B PRE-MESSENGER-RNA IN-VITRO BYSITE-SPECIFIC DEAMINATION OF ADENOSINE

EDITING Of the glutamate receptor subunit B (GluR-B) pre-mRNA at a sin gle adenosine residue results in an amino-acid change that profoundly alters the electrophysiological properties of the (1-7). Here we show that the GluR-B pre-mRNA is efficiently and accurately edited in vitro , and that base-pair interactions between the editing site and a seque nce in the downstream introns are required for substrate recognition. In addition, we directly demonstrate that editing results from the con version of adenosine to inosine by enzymatic deamination. The biochemi cal properties of this GluR-B editing activity are similar to those of a double-stranded-RNA-dependent adenosine deaminase(9-15), but RNA co mpetition and column fractionation experiments indicate that the GluR- B editing and deaminase activities are distinct. Thus, the GluR-B edit ing enzyme may contain the adenosine deaminase, or a similar activity, and an RNA recognition subunit that specifically targets the enzyme t o the editing site.