Regulation of phosphoenolpyruvate carboxykinase and insulin-like growth factor-binding protein-1 gene expression by insulin - The role of winged helix/forkhead proteins
Regulation of phosphoenolpyruvate carboxykinase and insulin-like growth factor-binding protein-1 gene expression by insulin - The role of winged helix/forkhead proteins
复制标题
DOI：
10.1074/jbc.m004898200
复制
发表时间：
2000-09-29
影响因子：
4.8
通讯作者：
Granner, DK
中科院分区：
文献类型：
--
作者：
Hall, RK;Yamasaki, T;Granner, DK
有翼螺旋/叉头（Fox）转录因子参与了许多胰岛素应答基因的调节。磷酸烯醇丙酮酸羧激酶（PEPCK）和胰岛素样生长因子结合蛋白-1（IGFBP-1）基因的胰岛素应答元件（IRE）结合Fox蛋白的FKHR和HNF 3亚类成员。先前对PEPCK和IGFBP-1 IRE的突变分析揭示了不影响HNF 3蛋白与这些元件的结合但确实消除了IRE介导胰岛素应答的能力的突变。这种结合和功能的分离提供了令人信服的证据，表明HNF 3蛋白本身不是胰岛素应答蛋白。在此使用相同的方法来确定FKHRL 1（Fox蛋白的FKHR亚类的成员）是否以与这些元件介导胰岛素应答的能力相关的方式结合PEPCK和IGFBP-1 IRE。FKHRL 1的过表达刺激从含有多聚化PEPCK IRE或IGFBP-1 IRE的转染报告基因构建体的转录，并且这种刺激被胰岛素抑制。突变型PEPCK和IGFBP-1 IRE结合FKHRL 1的能力与FKHRL 1过表达时介导FKHRL 1诱导转录的能力之间存在直接相关性。然而，在FKHRL 1不过度表达的条件下，FKHRL 1与突变型PEPCK和IGFBP-1 IRE的结合与这些元件介导胰岛素应答的能力之间缺乏相关性。因此，PEPCK和IGFBP-1 IRE介导FKHRL 1诱导的转录，并在该蛋白过度表达时通过胰岛素对其进行抑制，但在FKHRL 1的正常细胞浓度下，这些元件介导的胰岛素应答必须涉及另一种蛋白。
Winged helix/forkhead (Fox) transcription factors have been implicated in the regulation of a number of insulin-responsive genes. The insulin response elements (IREs) of the phosphoenolpyruvate carboxykinase (PEPCK) and insulin-like growth factor-binding protein-1 (IGFBP-1) genes bind members of the FKHR and HNF3 subclasses of Fox proteins. Previous mutational analyses of the PEPCK and IGFBP-1 IREs revealed mutations which do not affect the binding of HNF3 proteins to these elements but do eliminate the ability of the IREs to mediate an insulin response. This dissociation of binding and function provided compelling evidence that HNF3 proteins, per se, are not insulin response proteins. The same approach was used here to determine if FKHRL1, a member of the FKHR subclass of Fox proteins, binds to the PEPCK and IGFBP-1 IREs in a manner that correlates with the ability of these elements to mediate an insulin response. Overexpression of FKHRL1 stimulates transcription from transfected reporter constructs that contain a multimerized PEPCK IRE or an IGFBP-1 IRE and this stimulation is repressed by insulin. There is a direct correlation between the ability of mutant versions of the PEPCK and IGFBP-1 IREs to bind FKHRL1 and their ability to mediate FRHRL1-induced transcription when FKHRL1 is overexpressed. However, under conditions where FKHRL1 is not overexpressed, there is a lack of correlation between FKHRL1 binding to mutant versions of the PEPCK and IGFBP-1 IREs and the ability of these elements to mediate an insulin response. Therefore, the PEPCK and IGFBP-1 IREs mediate FKHRL1-induced transcription and its inhibition by insulin when this protein is overexpressed, but at the normal cellular concentration of FKHRL1 the insulin response mediated by these elements must involve another protein.