CREB activates the MafA promoter through proximal E-boxes and a CCAAT motif in pancreatic β-cells

• Published in: Journal of molecular endocrinology Vol. 73; no. 3; p. 1
• Main Authors: Aida, Yuki, Kataoka, Kohsuke
• Format: Journal Article
• Language: English
• Published: England Society for Endocrinology & BioScientifica Ltd 01.10.2024
• Subjects: Animal models; Beta cells; Beta2 protein; Cell culture; Cyclic AMP response element-binding protein; Diabetes mellitus (non-insulin dependent); Genomic analysis; Glucose transporter; Insulin secretion; Islet-1 protein; Pancreas; Preproinsulin; Regulatory sequences; Transcription activation; Transcription factors
• ISSN: 0952-5041; 1479-6813; 1479-6813
• DOI: 10.1530/JME-24-0023

MafA is a key transcriptional regulator of pancreatic islet β-cell function. Its target genes include those encoding preproinsulin and the glucose transporter Glut2 ( Slc2a2 ); thus, MafA function is essential for glucose-stimulated insulin secretion. Expression levels of MafA are reduced in β-cells of diabetic mouse models and human subjects, suggesting that β-cell dysfunction associated with type 2 diabetes is attributable to the loss of MafA. On the other hand, MafA is transcriptionally upregulated by incretin hormones through activation of CREB and its co-activator CRTC2. β-cell-specific expression of MafA relies on a distal enhancer element. However, the precise mechanism by which CREB-CRTC2 regulates the enhancer and proximal promoter regions of MafA remains unclear. In this report, we analyzed previously published ChIP-seq data and found that CREB and NeuroD1, a β-cell-enriched transactivator, bound to both the promoter and enhancer regions of human MAFA . A series of reporter assays revealed that CREB activated the enhancer through a conserved cAMP-responsive element (CRE) but stimulated MAFA promoter activity even when the putative CRE was deleted. Two E-box elements and a CCAAT motif, which bind NeuroD1 and ubiquitous NF-Y transcription factors, respectively, were necessary for transcriptional activation of the MAFA promoter by CREB. Genome-wide analysis of CREB-bound loci in β-cells revealed that they were enriched with CCAAT motifs. Furthermore, promoter analysis of the Isl1 gene encoding a β-cell-enriched transcription factor revealed that a CRE-like element and two CCAAT motifs, but not the E-box, were necessary for activation by CREB. These results provide clues to elucidate the detailed mechanism by which CREB regulates MafA as well as β-cell-specific genes.