De. Handy et al., A NEGATIVE REGULATORY ELEMENT IN THE PROMOTER REGION OF THE RAT ALPHA(2)A-ADRENERGIC RECEPTOR GENE OVERLAPS AN SP1 CONSENSUS BINDING-SITE, Biochemical journal, 311, 1995, pp. 541-547
Three subtypes of alpha(2)-adrenergic receptors (alpha(2)A, alpha(2)B
and alpha(2)C) have been described that differ in their primary sequen
ce and tissue-specific expression and are encoded by three distinct ge
nes. Previous work has shown that the human alpha(2)A-adrenergic recep
tor gene promoter consists of a TATA-box (TATAAA), palindromic sequenc
e (CCCACGTGGG) and GC-box (GGGGCGG) motif. Sequence analysis of the pu
tative promoter region of the rat alpha(2)A-adrenergic receptor gene s
howed that these promoter regions are conserved in their sequence and
relative location. We analysed the transcriptional activity of these r
egions using RINm5F, a rat insulinoma cell line that expresses the end
ogenous alpha(2)A-adrenergic receptor gene. These results showed that
the region from -484 to -92 has a negative effect on transcription, as
deletion of this region in alpha(2)A-adrenergic receptor gene-chloram
phenicol acetyltransferase reporter constructs increased reporter gene
activity. This region included the GC-box sequence which is a consens
us binding site for the nuclear factor SP1, which is a positive activa
tor of transcription. Gel-mobility-shift assays and supershift assays
with an antibody that recognizes SP1 showed binding of the SP1 nuclear
factor as well as other nuclear factors to this GC-box region. Additi
onal nuclear factors bind to the downstream palindromic region. We sug
gest that positive- and negative-acting nuclear factors contribute to
the activity of the alpha(2)-adrenergic receptor promoter.