Department of Pathology, Immunology, and Laboratory Medicine, University of Florida College of Medicine, Gainesville, Florida 32610, USA.
J Biol Chem. 2010 Apr 16;285(16):12181-9. doi: 10.1074/jbc.M109.064238. Epub 2010 Jan 27.
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.
肝核因子 1α（HNF1α）是胰腺β细胞发育和功能的关键调节因子，特别参与糖酵解和葡萄糖刺激的胰岛素分泌的调节。HNF1α 的异常表达导致 MODY3（年轻型成年发病型糖尿病 3 型）的发生。我们报告 NK6 同源框 1（NKX6.1）结合 HNF1α 启动子中的顺式调节元件，是β细胞中该基因的主要调节因子。我们在 HNF1α 启动子的远端区域鉴定出一个 NKX6.1 识别序列，并通过电泳迁移率变动和染色质免疫沉淀测定证实了 NKX6.1 在β细胞中的特异性结合。NKX6.1 核心结合序列的定点突变消除了 NKX6.1 介导的激活作用，并显著降低了β细胞中 HNF1α 启动子的活性。Nkx6.1 基因的过表达或小干扰 RNA 介导的敲低分别导致β细胞中 HNF1α 基因表达的增加或减少。我们的结论是，NKX6.1 是胰腺β细胞中 HNF1α 的新型调节因子。这种β细胞中 HNF1α 的新型调节机制可能为 MODY3 的诊断提供新的分子靶点。
