D. Fornasari et al., STRUCTURAL AND FUNCTIONAL-CHARACTERIZATION OF THE HUMAN ALPHA-3 NICOTINIC SUBUNIT GENE PROMOTER, Molecular pharmacology, 51(2), 1997, pp. 250-261
We describe the structural and functional features of the human alpha
3 nicotinic receptor subunit promoter. A 0.35-kb region immediately up
stream of the start codon was identified that when transfected in huma
n neuroblastoma cells was able to drive the expression of the lucifera
se reporter gene with a strength comparable to that of the well-charac
terized simian virus 40 promoter/enhancer. This region displayed the f
eatures of a multistart-site, GC-rich, TATA-less, and CAAT-less promot
er, containing many overlapping Sp1 and AP-2 putative binding sites. F
urther dissections of the 0.35-kb fragment revealed that its 3' region
, specifying the 5' UT of the mRNA, plays a relevant positive effect i
n determining the strength of the promoter. This region contains putat
ive cis-acting elements for AP-2, nuclear factor-kappa B, and the rece
ntly described multiple-start site element downstream-1. By mutation a
nalysis, we showed that these sites are functional and when combined i
ncrease the promoter activity by 4-fold. The 0.35-kb promoter was foun
d to be under the negative control of upstream sequences that include
a modern Alu repeat. The alpha 3 Alu repeat works as a composite regio
n, containing both positive and negative elements that control the act
ivity of the downstream promoter. Finally, we investigated the tissue-
specific activity of the human alpha 3 gene 5' regulatory sequences, s
howing that they are able to drive the expression of the reporter gene
preferentially in neuronal cells.