Distinct regulation of hepatic nuclear factor 1alpha by NKX6.1 in pancreatic beta cells.
Hepatic nuclear factor 1alpha (HNF1alpha) is a key regulator of development and function in pancreatic beta cells and is specifically involved in regulation of glycolysis and glucose-stimulated insulin secretion. Abnormal expression of HNF1alpha leads to development of MODY3 (maturity-onset diabetes of the young 3). We report that NK6 homeodomain 1 (NKX6.1) binds to a cis-regulatory element in the HNF1alpha promoter and is a major regulator of this gene in beta cells. We identified an NKX6.1 recognition sequence in the distal region of the HNF1alpha promoter and demonstrated specific binding of NKX6.1 in beta cells by electrophoretic mobility shift and chromatin immunoprecipitation assays. Site-directed mutagenesis of the NKX6.1 core-binding sequence eliminated NKX6.1-mediated activation and substantially decreased activity of the HNF1alpha promoter in beta cells. Overexpression or small interfering RNA-mediated knockdown of the Nkx6.1 gene resulted in increased or diminished HNF1alpha gene expression, respectively, in beta cells. We conclude that NKX6.1 is a novel regulator of HNF1alpha in pancreatic beta cells. This novel regulatory mechanism for HNF1alpha in beta cells may provide new molecular targets for the diagnosis of MODY3.
Donelan
William
W
Department of Pathology, Immunology, and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida 32610, USA.
Koya
Vijay
V
Li
Shi-Wu
SW
Yang
Li-Jun
LJ
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D003924:Diabetes Mellitus, Type 2 / Q000175:diagnosis / Q000235:genetics / Q000378:metabolism; D051538:Hepatocyte Nuclear Factor 1-alpha / Q000235:genetics*; D051557:Hepatocyte Nuclear Factor 4 / Q000235:genetics / Q000378:metabolism; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D050417:Insulin-Secreting Cells / Q000378:metabolism*; D051379:Mice; D016297:Mutagenesis, Site-Directed; D041681:NIH 3T3 Cells; D010957:Plasmids / Q000235:genetics; D011401:Promoter Regions, Genetic; D034741:RNA, Small Interfering / Q000235:genetics; D051381:Rats; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014162:Transfection
D017931:DNA Primers; C496487:HNF1A protein, human; D051538:Hepatocyte Nuclear Factor 1-alpha; D051557:Hepatocyte Nuclear Factor 4; C496593:Hnf4a protein, mouse; D018398:Homeodomain Proteins; C105201:NKX6-1 protein, human; D034741:RNA, Small Interfering; D011994:Recombinant Proteins