Transcription factor PHOX2A regulates the human α3 nicotinic receptor subunit gene promoter

PHOX2A is a paired-like homeodomain transcription factor that participates in specifying the autonomic nervous system. It is also involved in the transcriptional control of the noradrenergic neurotransmitter phenotype as it regulates the gene expression of tyrosine hydroxylase and dopamine-beta-hydroxylase. The results of this study show that the human orthologue of PHOX2A is also capable of regulating the transcription of the human alpha 3 nicotinic acetylcholine receptor gene, which encodes the ligand-binding subunit of the ganglionic type nicotinic receptor. In particular, we demonstrated by chromatin immunoprecipitation and DNA pulldown assays that PHOX2A assembles on the SacI-NcoI region of alpha 3 promoter and, by co-transfection experiments, that it exerts its transcriptional effects by acting through the 60-bp minimal promoter. PHOX2A does not seem to bind to DNA directly, and its DNA binding domain seems to be partially dispensable for the regulation of alpha 3 gene transcription. However, as suggested by the findings of our co-immunoprecipitation assays, it may establish direct or indirect protein-protein interactions with Sp1, thus regulating the expression of alpha 3 through a DNA-independent mechanism. As the alpha 3 subunit is expressed in every terminally differentiated ganglionic cell, this is the first example of a pan-autonomic gene whose expression is regulated by PHOX2 proteins.