ATF-2 stimulates the human insulin promoter through the conserved CRE2 sequence.
The insulin promoter contains a number of dissimilar cis-acting regulatory elements that bind a range of tissue specific and ubiquitous transcription factors. Of the regulatory elements within the insulin promoter, the cyclic AMP responsive element (CRE) binds by far the most diverse array of transcription factors. Rodent insulin promoters have a single CRE site, whereas there are four CREs within the human insulin gene, of which CRE2 is the only one conserved between species. The aim of this study was to characterise the human CRE2 site and to investigate the effects of the two principal CRE-associated transcription factors; CREB-1 and ATF-2. Co-transfection of INS-1 pancreatic beta-cells with promoter constructs containing the human insulin gene promoter placed upstream of the firefly luciferase reporter gene and expression plasmids for ATF-2 or CREB-1 showed that ATF-2 stimulated transcriptional activity while CREB-1 elicited an inhibitory effect. Mutagenesis of CRE2 diminished the effect of ATF-2 but not that of CREB-1. ATF-2 was shown to bind to the CRE2 site by electrophoretic mobility shift assay and by chromatin immunoprecipitation, while siRNA mediated knockdown of ATF-2 diminished the stimulatory effects of cAMP related signalling on promoter activity. These results suggest that ATF-2 may be a key regulator of the human insulin promoter possibly stimulating activity in response to extracellular signals.
Hay
Colin W
CW
School of Medical Sciences, University of Aberdeen, Institute of Medical Sciences, Foresterhill, Aberdeen, AB25 2ZD, UK.
Ferguson
Laura A
LA
Docherty
Kevin
K
D051698:Activating Transcription Factor 2 / Q000378:metabolism*; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002460:Cell Line; D005576:Colforsin / Q000378:metabolism; D017124:Conserved Sequence; D017362:Cyclic AMP Response Element-Binding Protein / Q000235:genetics / Q000378:metabolism; D006801:Humans; D007328:Insulin / Q000235:genetics*; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000378:metabolism; D051381:Rats; D020218:Response Elements; D015398:Signal Transduction / Q000235:genetics; D013004:Somatostatin / Q000235:genetics / Q000378:metabolism; D014162:Transfection
C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; C115163:CREB1 protein, human; D017362:Cyclic AMP Response Element-Binding Protein; D007328:Insulin; D034741:RNA, Small Interfering; D005576:Colforsin; D013004:Somatostatin