Chuang Hsiao-Ching, Chang Ching-Wen, Chang Geen-Dong, Yao Tso-Pang, Chen Hungwen
Graduate Institute of Biochemical Sciences, National Taiwan University, Taipei 106, Taiwan.
Nucleic Acids Res. 2006 Mar 9;34(5):1459-69. doi: 10.1093/nar/gkl048. Print 2006.
Human GCMa transcription factor regulates expression of syncytin, a placental fusogenic protein mediating trophoblastic fusion. Recently, we have demonstrated that CBP-mediated GCMa acetylation underlies the activated cAMP/PKA signaling pathway that stimulates trophoblastic fusion. Because protein acetylation is a reversible modification governed by histone acetyltransferases (HATs) and histone deacetylase (HDACs), in this study we investigated the key HDACs responsible for deacetylation of GCMa and thus the reduction in GCMa activity to avoid unwanted fusion events that may have adverse effects on placental morphogenesis. We herein demonstrate that the HDAC inhibitor, trichostatin A (TSA), increases the level of acetylated GCMa and that HDAC1, 3, 4 and 5 interact with and deacetylate GCMa. Glutathione S-transferase (GST) pull-down assays further verified direct interaction between GCMa and HDAC3 or CBP and HDAC3. HDAC3 counteracts the transcriptional coactivator activity of CBP and the enhancement effect of CBP on GCMa-mediated transcriptional activation. Correlatively, we found in placental cells that HDAC3 associates with the proximal GCMa-binding site (pGBS) in the syncytin promoter and dissociates from pGBS in the presence of forskolin, which stimulates the association of CBP and GCMa with pGBS. Our studies support that trophoblastic fusion in placental morphogenesis depends on the regulation of GCMa activity by HAT and HDAC.
人类GCMa转录因子调控合胞素的表达，合胞素是一种介导滋养层融合的胎盘融合蛋白。最近，我们已经证明，CBP介导的GCMa乙酰化是激活的cAMP/PKA信号通路的基础，该信号通路刺激滋养层融合。由于蛋白质乙酰化是一种由组蛋白乙酰转移酶（HATs）和组蛋白脱乙酰酶（HDACs）控制的可逆修饰，在本研究中，我们研究了负责GCMa去乙酰化从而导致GCMa活性降低的关键HDACs，以避免可能对胎盘形态发生产生不利影响的不必要的融合事件。我们在此证明，HDAC抑制剂曲古抑菌素A（TSA）可增加乙酰化GCMa的水平，并且HDAC1、3、4和5与GCMa相互作用并使其去乙酰化。谷胱甘肽S-转移酶（GST）下拉实验进一步验证了GCMa与HDAC3或CBP与HDAC3之间的直接相互作用。HDAC3抵消了CBP的转录共激活活性以及CBP对GCMa介导的转录激活的增强作用。相应地，我们在胎盘细胞中发现，HDAC3与合胞素启动子中的近端GCMa结合位点（pGBS）相关联，并且在福斯可林存在的情况下从pGBS解离，福斯可林刺激CBP和GCMa与pGBS的结合。我们的研究支持胎盘形态发生中的滋养层融合取决于HAT和HDAC对GCMa活性的调节。
