Molecular analysis of the multiple Golf alpha subunit mRNAs in the rat brain

The alpha subunit of GTP-binding protein Golf (G alpha olf), identified in the olfactory epithelium, in which it is supposed to mediate odorant-generated adenylyl cyclase activations, is much more expressed in the striatum than G alpha s, the classical stimulatory G protein alpha subunit (Hervé et al., J Neurosci., 13 (1993) 2237-2248). Four species of G alpha olf messenger RNA (mRNA) were observed by Northern blot in the rat striatum. Analysis of striatal G alpha olf cDNA clones demonstrated that despite extensive variations in their 5' and 3' untranslated regions, these four G alpha olf mRNAs encode the same G alpha olf polypeptide. One of the four mRNA species, which was selectively observed in the striatum, is generated by a novel promoter whose activity was barely detectable in the olfactory epithelium. Surprisingly, this promoter generates an unexpectedly high proportion of transcripts in which the first intron is unspliced. The retention of intron was found to abolish the translation of G alpha olf mRNA in the reticulocyte lysate system, suggesting that it could be involved in the down regulation of G alpha olf expression in the striatum. Furthermore, a new polyadenylation site with a non canonical sequence, AATACA, was found to be responsible of the two shortest forms of G alpha olf mRNA. In conclusion, we have shown that the G alpha olf proteins present in the striatum and the olfactory epithelium are identical and that multiple variations in the untranslated parts of the mRNAs could affect G alpha olf expression.