Cooperative regulation of endogenous cAMP-response element binding protein and CCAAT/enhancer-binding protein β in GH-stimulated c-fos expression
Cooperative regulation of endogenous cAMP-response element binding protein and CCAAT/enhancer-binding protein β in GH-stimulated c-fos expression
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DOI：
10.1677/joe-07-0169
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发表时间：
2008-01-01
影响因子：
4
通讯作者：
Schwartz, Jessica
中科院分区：
文献类型：
--
作者：
Cui, Tracy Xiao;Kwok, Roland;Schwartz, Jessica
GH通过调节多种转录因子激活c-fos启动子。这项研究增加了我们的理解GH调节转录，表明GH调节c-fos cAMP反应元件（CRE）和它的结合蛋白，CREB。GH对c-fos启动子的激活受显性负性A-CREB表达的影响。在3 T3-F442 A前脂肪细胞中，GH刺激CREB在Ser 133（P-CREB）的快速和瞬时磷酸化，这是CREB反式激活的关键位点。该残基的突变会损害GH诱导的c-fos表达，表明CREB在Ser 133处的磷酸化有助于GH诱导的c-fos激活。MEK抑制剂UO 126损害CREB和C/EBP β的磷酸化，表明ERK介导这两种蛋白质的磷酸化。UO 126，而不是蛋白激酶A抑制剂H89，阻断GH诱导的c-fos mRNA的表达。CREB和C/EBP β的组合增强了c-fos启动子的激活，CRE的突变削弱了这种增强，以及GH刺激的c-fos激活。GH处理增加了c-fos启动子上内源性磷酸化CREB和磷酸化C/EBP β的占用率。铀-126削弱了这种增加。GH诱导激活的P-CREB和P-C/EBP β占据相同的c-fos启动子DNA，提示它们可能参与GH调控的c-fos复合体。这些发现表明，协调磷酸化CREB和C/EBP β在响应GH是由ERK 1/2介导的，磷酸化的蛋白质是一个调节复合物的一部分，占据c-fos在体内调节c-fos转录合作响应GH。
GH activates the c-fos promoter by regulating multiple transcription factors. This study adds to our understanding of GH-regulated transcription by demonstrating that GH regulates the c-fos cAMP-response element (CRE) and its binding protein, CREB. Activation of the c-fos promoter by GH is impaired by expression of dominant-negative A-CREB. GH stimulates rapid and transient phosphorylation of CREB at Ser 133 (P-CREB), a critical site for transactivation by CREB, in 3T3-F442A preadipocytes. Mutation of this residue impairs GH-induced c-fos expression, suggesting that phosphorylation of CREB at Ser 133 contributes to GH-induced c-fos activation. The MEK inhibitor UO126 impaired the phosphorylation of CREB and that of C/EBP beta, suggesting that ERKs mediate the phosphorylation of both proteins. UO126, but not the protein kinase A inhibitor H89, blocked GH-induced c-fos mRNA expression. A combination of CREB and C/EBP beta enhanced c-fos promoter activation, and mutation of the CRE impaired the enhancement, as well as GH-stimulated c-fos activation. GH treatment increased the occupancy of both endogenous phospho-CREB and phospho-C/EBP beta on the c-fos promoter. The increases were impaired by UO126. The active P-CREB and P-C/EBP beta are induced by GH to occupy the same c-fos promoter DNA, suggesting that they may participate in a GH-regulated complex on c-fos. These findings suggest that coordinated phosphorylation of CREB and C/EBP beta in response to GH is mediated by ERK1/2, and that the phosphorylated proteins are part of a regulatory complex that occupies c-fos in vivo to regulate c-fos transcription cooperatively in response to GH.