Nakatani Teruyo, Partridge Nicola C
Department of Basic Science and Craniofacial Biology, New York University College of Dentistry, New York, New York 10010.
Endocrinology. 2017 Nov 1;158(11):3778-3791. doi: 10.1210/en.2017-00159.
Parathyroid hormone (PTH) regulates the transcription of many genes in the osteoblast. One of these genes is Mmp13, which is involved in bone remodeling and early stages of endochondral bone formation. Previously, we reported that PTH induces Mmp13 transcription by regulating the dissociation of histone deacetylase 4 (HDAC4) from runt-related transcription factor 2 (Runx2), and the association of the HATs, p300, and p300/CREB binding protein (CBP)-associated factor. It is known that, in addition to Runx2, HDAC4 binds to the transcription factor, myocyte-specific enhancer factor 2c (MEF2C), and represses its activity. In this work, we investigated whether MEF2C participates in PTH-stimulated Mmp13 gene expression in osteoblastic cells and how it does so. Knockdown of Mef2c in UMR 106-01 cells repressed Mmp13 messenger RNA expression and promoter activity with or without PTH treatment. Chromatin immunoprecipitation (ChIP) assays showed that MEF2C associated with the Mmp13 promoter; this increased after 4 hours of PTH treatment. ChIP-reChIP results indicate that endogenous MEF2C associates with HDAC4 on the Mmp13 promoter; after PTH treatment, this association decreased. From gel shift, ChIP, and promoter-reporter assays, MEF2C was found to associate with the activator protein-1 (AP-1) site without directly binding to DNA and had its stimulatory effect through interaction with c-FOS. In conclusion, MEF2C is necessary for Mmp13 gene expression at the transcriptional level and participates in PTH-stimulated Mmp13 gene expression by increased binding to c-FOS at the AP-1 site in the Mmp13 promoter. The observation of MEF2C interacting with a member of the AP-1 transcription factor family provides knowledge of the functions of HDAC4, c-FOS, and MEF2C.
甲状旁腺激素（PTH）调节成骨细胞中许多基因的转录。其中一个基因是Mmp13，它参与骨重塑和软骨内骨形成的早期阶段。此前，我们报道PTH通过调节组蛋白去乙酰化酶4（HDAC4）与 runt相关转录因子2（Runx2）的解离以及组蛋白乙酰转移酶（HATs）、p300和p300/CREB结合蛋白（CBP）相关因子的结合来诱导Mmp13转录。已知除了Runx2外，HDAC4还与转录因子肌细胞特异性增强因子2c（MEF2C）结合并抑制其活性。在这项研究中，我们调查了MEF2C是否参与成骨细胞中PTH刺激的Mmp13基因表达以及它是如何参与的。在UMR 106-01细胞中敲低Mef2c可抑制Mmp13信使核糖核酸表达和启动子活性，无论是否进行PTH处理。染色质免疫沉淀（ChIP）分析表明，MEF2C与Mmp13启动子相关；PTH处理4小时后这种相关性增加。ChIP再免疫沉淀结果表明，内源性MEF2C在Mmp13启动子上与HDAC4相关；PTH处理后，这种相关性降低。通过凝胶迁移、ChIP和启动子报告基因分析发现，MEF2C与激活蛋白-1（AP-1）位点相关，但不直接结合DNA，并且通过与c-FOS相互作用发挥其刺激作用。总之，MEF2C在转录水平上对Mmp13基因表达是必需的，并且通过增加在Mmp13启动子的AP-1位点与c-FOS的结合来参与PTH刺激的Mmp13基因表达。MEF2C与AP-1转录因子家族成员相互作用的观察为HDAC4、c-FOS和MEF2C的功能提供了认识。
