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.
RESEARCH DESIGN AND 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.
- Aryl Hydrocarbon Receptor Nuclear Translocator/antagonists & inhibitors
- Cell Culture Techniques
- Chromatin/isolation & purification
- DNA Primers
- Gene Expression Regulation/physiology
- Insulin-Secreting Cells/cytology
- Mice, Inbred Strains
- Nuclear Proteins/metabolism
- Oligonucleotide Array Sequence Analysis
- Polymerase Chain Reaction
- Promoter Regions, Genetic
- Transcription Factors/metabolism