Epigenetic mechanisms in the dopamine D2 receptor-dependent inhibition of the prolactin gene
Epigenetic mechanisms in the dopamine D2 receptor-dependent inhibition of the prolactin gene
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DOI：
10.1210/me.2004-0111
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发表时间：
2005-07-01
影响因子：
--
通讯作者：
Elsholtz, HP
中科院分区：
文献类型：
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作者：
Liu, JC;Baker, RE;Elsholtz, HP
催乳素基因的转录受到靶向调控启动子区域的正、负激素信号的动态控制。基于组蛋白去乙酰化酶（hdac）抑制剂对催乳素基因表达的诱导作用，我们研究了基因组催乳素启动子上组蛋白乙酰化作为转录调控的后期步骤的作用。GH4细胞的染色质免疫沉淀分析显示，与下游内含子序列相比，该基因的启动子和增强子区域的乙酰化组蛋白水平升高。17 β -雌二醇在30分钟内刺激启动子区域组蛋白H4乙酰化2- 3倍。多巴胺在30分钟内抑制组蛋白H4乙酰化2倍，这种作用被MAPK激酶（MEK1）抑制剂U0126模仿。相比之下，合成糖皮质激素地塞米松，抑制催乳素转录，未能改变组蛋白乙酰化在相同的时间框架。转录激活子Pit-1与催乳素启动子的关联在激素治疗下没有改变。然而，在多巴胺的作用下，组蛋白去乙酰化酶HDAC2和协同抑制因子mSin3A被迅速募集到催乳素启动子上，并在1小时内维持高于基础水平的关联。与这种协同抑制因子的功能一致，小干扰RNA消耗内源性mSin3A足以使催乳素基因表达增加70%，与HDAC抑制剂trichostatin a的诱导作用相当。这些研究表明，多巴胺D2受体的激活和MAPK （ERK1/2）信号的抑制导致催乳素基因组启动子组蛋白的快速去乙酰化。特异性HDAC/辅抑制复合物的募集可能是Gi/o偶联受体抑制靶基因转录的重要机制。
Transcription of the prolactin gene is dynamically controlled by positive and negative hormone signals that target the regulatory promoter region. Based on the inducibility of prolactin gene expression by inhibitors of histone deacetylases (HDACs), we examined the role of histone acetylation at the genomic prolactin promoter as a late step in transcriptional regulation. Chromatin immunoprecipitation analysis of GH4 cells revealed elevated levels of acetylated histones in the promoter and enhancer regions of the gene, compared with downstream intron sequences. 17 beta-Estradiol stimulated histone H4 acetylation in the promoter region by 2- to 3-fold within 30 min. Dopamine inhibited histone H4 acetylation by 2- fold in 30 min, an effect mimicked by the MAPK kinase (MEK1) inhibitor U0126. In contrast, the synthetic glucocorticoid dexamethasone, which inhibits prolactin transcription, failed to alter histone acetylation over the same time frame. Association of transcription activator Pit-1 with the prolactin promoter was unchanged by hormone treatment. However, in response to dopamine, histone deacetylase HDAC2 and corepressor mSin3A were rapidly recruited to the prolactin promoter, and association was sustained above basal levels over a 1-h period. Consistent with this corepressor function, depletion of endogenous mSin3A by small interfering RNA was sufficient to enhance prolactin gene expression by 70%, comparable to the induction by the HDAC inhibitor, trichostatin A. These studies demonstrate that dopamine D2 receptor activation and inhibition of MAPK (ERK1/2) signaling lead to rapid deacetylation of histones at the genomic prolactin promoter. Recruitment of specific HDAC/ corepressor complexes may be an important mechanism for repression of target gene transcription by Gi/o-coupled receptors.