Neuronal expression of the rat M-1 muscarinic acetylcholine receptor gene is regulated by elements in the first exon

Muscarinic acetylcholine receptor genes are members of the G-protein couple d receptor superfamily. Each member of this family studied to dale appears to have a distinct expression profile, however the mechanisms determining t hese expression patterns remain largely unknown. We have previously isolate d a genomic clone containing the M-1 muscarinic receptor gene and determine d its gene structure [Pepitoni, Wood and Buckley (1997) J. Biol. Chem, 272, 17112-17117], We have now identified DNA elements responsible for driving cell specific expression in transient transfection assays of immortalized c ell lines. A region of the gene spanning 974 nucleotides and containing 602 nucleotides of the first exon is sufficient to drive specific expression i n cell lines. Like the M-4 and M-2 gene promoters, the M-1 promoter contain s an Spl motif which can recruit transcription factor Spl and at least one other protein, although this site does not appear to be functionally import ant for M-1 expression in our assay. We have identified a region within the first exon of the M-1 gene that regulates expression in cell lines, contai ns several positive and negative acting elements and is able to drive expre ssion of a heterologous promoter. A polypyrimidine/polypurine tract and a s equence conserved between M-1 genes of various species act in concert to en hance M-1 transcription and are able to activate a heterologous promoter. W e show that DNA binding proteins interact in vitro with single-stranded DNA derived from these regions and suggest that topology of the DNA is importa nt for regulation of M-1 expression.