DAF-16 recruits the CREB-binding protein coactivator complex to the insulin-like growth factor binding protein 1 promoter in HepG2 cells
DAF-16 recruits the CREB-binding protein coactivator complex to the insulin-like growth factor binding protein 1 promoter in HepG2 cells
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DOI：
10.1073/pnas.190326997
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发表时间：
2000-09-12
影响因子：
11.1
通讯作者：
Alexander-Bridges, MC
中科院分区：
文献类型：
--
作者：
Nasrin, N;Ogg, S;Alexander-Bridges, MC
胰岛素通过胰岛素反应元件（IRE）负性调节胰岛素样生长因子结合蛋白1 （IGFBP-1）基因的表达，IRE也有助于糖皮质激素刺激该基因。我们发现秀丽隐杆线虫蛋白DAF-16与IGFBP-1 IRE结合，其特异性与叉头（FKH）因子相似，叉头（FKH）因子既能增强糖皮质激素的反应性，又能介导胰岛素在该位点的负作用。在HepG2细胞中，DAF-16及其哺乳动物同源物FKHR， FKHRL1。和AFX，通过IGFBP-1.IRE激活转录；这种作用被病毒癌蛋白E1A所抑制，但不被不能与p300/ creb结合蛋白（CBP）相互作用的E1A突变体所抑制。我们发现DAF-16和FKHR可以与p300/CBP的KIX和E1A/SRC相互作用域以及类固醇受体共激活因子（SRC）相互作用。在线虫中，DAF-16的c端缺失突变体不能结合CBP的KIX结构域，不能通过IGFBP-1- ire激活转录，并且抑制糖皮质激素对IGFBP-1启动子的激活。因此，DAF-16同源物与CBP的KIX结构域的相互作用对于基础和糖皮质激素刺激的转激活是必不可少的。尽管AFX与CBP的KIX结构域相互作用，但它不与SRC相互作用，也不响应糖皮质激素或胰岛素。因此，我们得出结论，DAF-16和FKHR作为糖皮质激素反应的辅助因子，通过将p300/CBP/SRC共激活因子复合物募集到IGFBP-1启动子中的FKH因子位点，从而允许细胞整合糖皮质激素和胰岛素对携带该位点的基因的影响。
Insulin negatively regulates expression of the insulin-like growth factor binding protein 1 (IGFBP-1) gene by means of an insulin-responsive element (IRE) that also contributes to glucocorticoid stimulation of this gene. We find that the Caenorhabditis elegans protein DAF-16 binds the IGFBP-1 IRE with specificity similar to that of the forkhead (FKH) factor(s) that act both to enhance glucocorticoid responsiveness and to mediate the negative effect of insulin at this site. In HepG2 cells, DAF-16 and its mammalian homologs, FKHR, FKHRL1. and AFX, activate transcription through the IGFBP-1.IRE; this effect is inhibited by the viral oncoprotein E1A, but not by mutants of E1A that fail to interact with the coactivator p300/CREB-binding protein (CBP), We show that DAF-16 and FKHR can interact with both the KIX and E1A/SRC interaction domains of p300/CBP, as well as the steroid receptor coactivator (SRC). A C-terminal deletion mutant of DAF-16 that is nonfunctional in C. elegans fails to bind the KIX domain of CBP, fails to activate transcription through the IGFBP-1-IRE, and inhibits activation of the IGFBP-1 promoter by glucocorticoids. Thus, the interaction of DAF-16 homologs with the KIX domain of CBP is essential to basal and glucocorticoid-stimulated transactivation, Although AFX interacts with the KIX domain of CBP, it does not interact with SRC and does not respond to glucocorticoids or insulin. Thus, we conclude that DAF-16 and FKHR act as accessory factors to the glucocorticoid response, by recruiting the p300/CBP/SRC coactivator complex to an FKH factor site in the IGFBP-1 promoter, which allows the cell to integrate the effects of glucocorticoids and insulin on genes that carry this site.