RGD Reference Report - Elevated glucose attenuates human insulin gene promoter activity in INS-1 pancreatic beta-cells via reduced nuclear factor binding to the A5/core and Z element. - Rat Genome Database

RGD Reference Report - Elevated glucose attenuates human insulin gene promoter activity in INS-1 pancreatic beta-cells via reduced nuclear factor binding to the A5/core and Z element. - Rat Genome Database

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Elevated glucose attenuates human insulin gene promoter activity in INS-1 pancreatic beta-cells via reduced nuclear factor binding to the A5/core and Z element.
Authors:	Pino, MF Ye, DZ Linning, KD Green, CD Wicksteed, B Poitout, V Olson, LK
Citation:	Pino MF, etal., Mol Endocrinol. 2005 May;19(5):1343-60. Epub 2005 Jan 13.
RGD ID:	2311185
Pubmed:	PMID:15650027 (View Abstract at PubMed)
DOI:	DOI:10.1210/me.2003-0493 (Journal Full-text)
Chronic exposure of pancreatic beta-cells to elevated glucose reduces insulin gene promoter activity, and this is associated with diminished binding of two beta-cell-enriched transcription factors, Pdx-1 and MafA. In this study using INS-1 beta-cells, overexpression of MafA, but not Pdx-1, was able to restore expression of a human insulin reporter gene (-327 to +30 bp) suppressed by elevated glucose. At issue, however, was that MafA also markedly stimulated an insulin reporter gene (-230 to +30 bp) that was only marginally suppressed by glucose, suggesting that glucose-mediated suppression of the insulin promoter involved elements upstream of -230. Using serial truncations and mini-enhancer constructs of the human insulin promoter, the majority of glucose suppression was localized to regulatory elements between -327 and -261. Nuclear extracts from INS-1 cells exposed to elevated glucose had reduced binding activities to the A5/core (-319 to -307), and to a palindrome (-284 to -267) and an E box (-273 to -257, E3) contained within the Z element. The A5/core binding complex was determined to contain MafA, Pdx-1, and an A2-like binding factor. Two mini-enhancer constructs containing the A5/core were suppressed by glucose and strongly activated by MafA. Glucose-mediated suppression of the Z mini-enhancer was not attenuated by overexpression of MafA or Pdx-1. Site-directed mutation of the A5/core, palindrome, and E3 elements attenuated glucose-mediated suppression. These data indicate that glucose suppression of human insulin promoter activity in INS-1 cells involves reduced binding of MafA to the A5/core. Changes in nuclear factor binding to the Z element, which functions as a strong activator element in primary islets and a negative regulatory element in simian virus 40 or T antigen transformed beta-cell lines, also participate in glucose suppression of insulin promoter activity.

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Object Symbol	Species	Term	Qualifier	Evidence	With	Notes	Source	Original Reference(s)
Pdx1	Rat	protein-containing complex binding		IDA		MafA and A2 binding factor	RGD

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Genes (Rattus norvegicus)

Pdx1 (pancreatic and duodenal homeobox 1)

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