Fass Daniel M, Butler Jennifer E F, Goodman Richard H
Vollum Institute L474, Oregon Health and Science University, Portland, Oregon 97239, USA.
J Biol Chem. 2003 Oct 31;278(44):43014-9. doi: 10.1074/jbc.M305905200. Epub 2003 Aug 25.
Many hormones activate transcription by raising the level of cAMP within cells. In one well studied pathway, cAMP induces protein kinase A to phosphorylate the transcription factor CREB, which binds to a consensus sequence, the cAMP-regulated enhancer, found in many target genes. A generally accepted model suggests that phosphorylated CREB recruits the histone acetyltransferase CBP to activate transcription. In contrast, histone deacetylases have been linked to the cessation of CREB-dependent transcription. Here we tested this model in the regulation of endogenous CREB target genes. We used a constitutively active CREB mutant and microarray analysis to identify target genes in PC12 cells. We then tested the role of histone deacetylase activity in cAMP activation of four of these genes (c-FOS, ICER, NOR-1, and NUR77) by treating cells with the histone deacetylase inhibitor trichostatin A. Consistent with the generally accepted model, trichostatin A enhanced activation of c-FOS and NUR77 by cAMP. Surprisingly, trichostatin A blocked activation of ICER and NOR-1. The block of ICER and NOR-1 activation persisted in the presence of cycloheximide, indicating that the trichostatin A effect did not depend on new protein synthesis. This unexpected role of histone deacetylases in transcriptional activation of certain endogenous CREB target genes was not apparent in transfected reporter genes. Chromatin immunoprecipitation analysis indicated that the differential roles of histone deacetylases in activating or repressing CREB target genes was manifested at the level of preinitiation complex recruitment. These data indicate that histone deacetylases differentially regulate CREB target genes by contributing to either activation or cessation of transcription.
许多激素通过提高细胞内cAMP水平来激活转录。在一条经过充分研究的信号通路中，cAMP诱导蛋白激酶A磷酸化转录因子CREB，CREB会结合到许多靶基因中都存在的共有序列——cAMP调节增强子上。一个被广泛接受的模型表明，磷酸化的CREB招募组蛋白乙酰转移酶CBP来激活转录。相反，组蛋白去乙酰化酶与CREB依赖性转录的终止有关。在这里，我们在内源性CREB靶基因的调控中对该模型进行了测试。我们使用组成型活性CREB突变体和微阵列分析来鉴定PC12细胞中的靶基因。然后，我们通过用组蛋白去乙酰化酶抑制剂曲古抑菌素A处理细胞，测试了组蛋白去乙酰化酶活性在cAMP对其中四个基因（c-FOS、ICER、NOR-1和NUR77）激活过程中的作用。与普遍接受的模型一致，曲古抑菌素A增强了cAMP对c-FOS和NUR77的激活作用。令人惊讶的是，曲古抑菌素A阻断了ICER和NOR-1的激活。在存在放线菌酮的情况下，ICER和NOR-1激活的阻断仍然存在，这表明曲古抑菌素A的作用不依赖于新的蛋白质合成。组蛋白去乙酰化酶在某些内源性CREB靶基因转录激活中的这种意外作用在转染的报告基因中并不明显。染色质免疫沉淀分析表明，组蛋白去乙酰化酶在激活或抑制CREB靶基因中的不同作用在起始前复合物募集水平上表现出来。这些数据表明，组蛋白去乙酰化酶通过促进转录的激活或终止来差异调节CREB靶基因。
