Carbohydrate-responsive element-binding protein (ChREBP) is a negative regulator of ARNT/HIF-1beta gene expression in pancreatic islet beta-cells.
OBJECTIVE
Carbohydrate-responsive element-binding protein (ChREBP) is a transcription factor that has been shown to regulate carbohydrate metabolism in the liver and pancreatic beta-cells in response to elevated glucose concentrations. Because few genes have been identified so far as bona fide ChREBP-target genes, we have performed a genome-wide analysis of the ChREBP transcriptome in pancreatic beta-cells.


METHODS
Chromatin immunoprecipitation and high-density oligonucleotide tiling arrays (ChIP-chip; Agilent Technologies) using MIN6 pancreatic beta-cell extracts were performed together with transcriptional and other analysis using standard techniques.


RESULTS
One of the genes identified by ChIP-chip and linked to glucose sensing and insulin secretion was aryl hydrocarbon receptor nuclear translocator (ARNT)/hypoxia-inducible factor-1beta (HIF-1beta), a transcription factor implicated in altered gene expression and pancreatic-islet dysfunction in type 2 diabetes. We first confirmed that elevated glucose concentrations decreased ARNT/HIF-1beta levels in INS-1 (832/13) cells and primary mouse islets. Demonstrating a role for ChREBP in ARNT gene regulation, ChREBP silencing increased ARNT mRNA levels in INS-1 (832/13) cells, and ChREBP overexpression decreased ARNT mRNA in INS-1 (832/13) cells and primary mouse islets. We demonstrated that ChREBP and Max-like protein X (MLX) bind on the ARNT/HIF-1beta promoter on the proximal region that also confers the negative glucose responsiveness.


CONCLUSIONS
These results demonstrate that ChREBP acts as a novel repressor of the ARNT/HIF-1beta gene and might contribute to beta-cell dysfunction induced by glucotoxicity.
Noordeen
Nafeesa A
NA
Department of Endocrinology and Metabolic Medicine, Division of Medicine, Imperial College, London, U.K.
Khera
Tarnjit K
TK
Sun
Gao
G
Longbottom
E Rebecca
ER
Pullen
Timothy J
TJ
da Silva Xavier
Gabriela
G
Rutter
Guy A
GA
Leclerc
Isabelle
I
D000818:Animals; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator / Q000037:antagonists & inhibitors / Q000235:genetics*; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D018929:Cell Culture Techniques; D002843:Chromatin / Q000302:isolation & purification; D017931:DNA Primers; D005786:Gene Expression Regulation / Q000502:physiology*; D005947:Glucose / Q000633:toxicity; D050417:Insulin-Secreting Cells / Q000166:cytology / Q000502:physiology*; D008297:Male; D051379:Mice; D008815:Mice, Inbred Strains; D009687:Nuclear Proteins / Q000378:metabolism / Q000502:physiology*; D020411:Oligonucleotide Array Sequence Analysis; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics / Q000302:isolation & purification; D051381:Rats; D014157:Transcription Factors / Q000378:metabolism / Q000502:physiology*; D014162:Transfection
C497397:Arnt protein, mouse; D051778:Basic Helix-Loop-Helix Leucine Zipper Transcription Factors; D002843:Chromatin; D017931:DNA Primers; C506001:Mlxipl protein, mouse; D009687:Nuclear Proteins; D014157:Transcription Factors; D051784:Aryl Hydrocarbon Receptor Nuclear Translocator; D012313:RNA; D005947:Glucose