The helix-loop-helix transcription factor SEF-2 regulates the activity of a novel initiator element in the promoter of the human somatostatin receptor II gene.
The effects of somatostatin hormones are mediated by a family of five different seven-helix transmembrane spanning receptors (SSTR1-5). The expression of the five different SSTR subtypes displays a complex temporal- and tissue-specific pattern. To investigate the molecular mechanisms controlling the different expression patterns of the SSTRs, we cloned the 5'-flanking region of the human SSTR2 gene. Characterization of the SSTR2 promoter resulted in the identification of a novel initiator element (SSTR2inr). Transcriptional activity of the SSTR2inr is dependent on the presence of a binding site (E-box) for basic helix-loop-helix (bHLH) transcription factors. By screening a mouse brain cDNA expression library we isolated a cDNA coding for the bHLH transcription factor SEF-2. SEF-2 binds to the E-box present in the SSTR2inr, both in vitro and in vivo and activates transcription from the SSTR2inr. A single point mutation within the E-box eliminates binding of SEF-2 and results in a complete loss of transcriptional activity of the SSTR2inr. Furthermore, DNA binding studies demonstrate that the basal transcription factor TFIIB can be tethered to the SSTR2inr through physical interaction with SEF-2. In summary, the SSTR2inr represents a novel type of initiator element that confers gene expression in the absence of a TATA-box or binding sites for other known initiator factors, like YY-1 or USF.
Pscherer
A
A
Institut für Pathologie, Universität Regensburg, Germany.
Dörflinger
U
U
Kirfel
J
J
Gawlas
K
K
Rüschoff
J
J
Buettner
R
R
Schüle
R
R
D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D001665:Binding Sites; D004247:DNA / Q000737:chemistry / Q000378:metabolism; D017931:DNA Primers; D004268:DNA-Binding Proteins; D018257:Helix-Loop-Helix Motifs; D006801:Humans; D008156:Luciferases / Q000096:biosynthesis; D051379:Mice; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D017481:Receptors, Somatostatin / Q000096:biosynthesis* / Q000235:genetics*; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D016385:TATA Box; D051820:TCF Transcription Factors; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors / Q000737:chemistry / Q000378:metabolism*; D014158:Transcription, Genetic
D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D017931:DNA Primers; D004268:DNA-Binding Proteins; D009419:Nerve Tissue Proteins; D017481:Receptors, Somatostatin; D011993:Recombinant Fusion Proteins; D051820:TCF Transcription Factors; C532096:TCF4 protein, human; C544894:TCF7L2 protein, human; C090743:Tcf4 protein, mouse; C544895:Tcf7l2 protein, mouse; D000073940:Transcription Factor 4; D058118:Transcription Factor 7-Like 2 Protein; D014157:Transcription Factors; D004247:DNA; C093733:somatostatin receptor 2; D008156:Luciferases