Alpha3 and alpha5 neuronal nicotinic receptor subunit genes : a case of tail-to-tail overlap in humans

Natural antisense transcripts, because of their potential to form double-stranded RNA (dsRNA) molecules, recently emerged as a mechanism acting on eukaryotic gene regulation at multiple levels. CHRNA3 and CHRNA5, coding for alpha3 and alpha5 subunits of the neuronal nicotinic acetylcholine receptor, have been reported to overlap at their 3'ends in human and bovine genomes. The general goal of this PhD project was the structural and functional study of this overlap. A fine characterization of human CHRNA3 and CHRNA5 alternative transcripts allowed a more precise definition of the overlap extent and highlighted a complex web of possible sense-antisense interactions among overlapping mRNAs. An RNase protection-based approach was used to detect in vivo RNA-RNA duplexes of CHRNA3 and CHRNA5 transcripts, which resulted to be present in human but not in bovine cells. Furthermore, levels of overlapping transcripts were determined by real-time RT-PCR both in humans and in cattle. Finally, some possible functional consequences of this overlap were explored.