Characterization of the human SLC30A8 promoter and intronic enhancer

Department of Molecular Physiology and Biophysics, Vanderbilt University School of Medicine, 8415 MRB IV, 2213 Garland Avenue, Nashville, Tennessee 37232-0615, USA.
Journal of Molecular Endocrinology (Impact Factor: 3.08). 07/2011; 47(3):251-9. DOI: 10.1530/JME-11-0055
Source: PubMed


Genome-wide association studies have shown that a polymorphic variant in SLC30A8, which encodes zinc transporter-8, is associated with altered susceptibility to type 2 diabetes (T2D). This association is consistent with the observation that glucose-stimulated insulin secretion is decreased in islets isolated from Slc30a8 knockout mice. In this study, immunohistochemical staining was first used to show that SLC30A8 is expressed specifically in pancreatic islets. Fusion gene studies were then used to examine the molecular basis for the islet-specific expression of SLC30A8. The analysis of SLC30A8-luciferase expression in βTC-3 cells revealed that the proximal promoter region, located between -6154 and -1, relative to the translation start site, was only active in stable but not transient transfections. VISTA analyses identified three regions in the SLC30A8 promoter and a region in SLC30A8 intron 2 that are conserved in the mouse Slc30a8 gene. Additional fusion gene experiments demonstrated that none of these Slc30a8 promoter regions exhibited enhancer activity when ligated to a heterologous promoter whereas the conserved region in SLC30A8 intron 2 conferred elevated reporter gene expression selectively in βTC-3 but not in αTC-6 cells. Finally, the functional effects of a single nucleotide polymorphism (SNP), rs62510556, in this conserved intron 2 enhancer were investigated. Gel retardation studies showed that rs62510556 affects the binding of an unknown transcription factor and fusion gene analyses showed that it modulates enhancer activity. However, genetic analyses suggest that this SNP is not a causal variant that contributes to the association between SLC30A8 and T2D, at least in Europeans.

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    • "Moreover, gene repression is sometimes dependent on chromosome-embedment and additional sequences located either far away from the promoter in 5′ as described for the PEPCK gene promoter under insulin treatment [31], or even within the 3′ region in the intronic sequence might account for the insulin-dependent downregulation of HSD11B2. A sequence alignment using the VISTA program shows some sequences well conserved in intron I that could potentially act as intronic enhancers (Fig. S2) [32]. "
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