NFATc1 mediates HDAC-dependent transcriptional repression of osteocalcin expression during osteoblast differentiation.
NFATc1 mediates HDAC-dependent transcriptional repression of osteocalcin expression during osteoblast differentiation.
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DOI：
10.1016/j.bone.2009.05.009
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发表时间：
2009-09
期刊：
影响因子：
4.1
通讯作者：
Zayzafoon, Majd
中科院分区：
文献类型：
--
作者：
Choo, Min-Kyung;Yeo, Hyeonju;Zayzafoon, Majd
我们以前报道过，在体内和体外抑制活化T细胞核因子（NFAT）信号增加成骨细胞分化和骨形成。为了研究NFATc 1调节成骨细胞分化的机制，我们建立了一个成骨细胞系，过表达组成型活性NFATc 1（ca-NFATc 1）。NFATc 1的激活显著抑制成骨细胞的分化和功能，表现为碱性磷酸酶活性和矿化的抑制以及成骨细胞分化的早期和晚期标志物（如osterix和骨钙素）的基因表达的降低。通过关注NFATc 1在晚期分化过程中的特定作用，我们发现NFATc 1对骨钙素基因表达的抑制与骨钙素启动子活性的抑制以及TCF/LEF反式激活的减少有关。此外，NFATc 1的过度表达完全阻断了成骨细胞分化过程中总组蛋白去乙酰化酶（HDAC）活性的降低，并阻止了组蛋白H3和H4的过度乙酰化。从机制上讲，我们通过染色质免疫沉淀（ChIP）试验表明，NFATc 1的过表达维持了骨钙素启动子近端区域上HDAC 3的结合，导致组蛋白H3和H4与表达GFP的成骨细胞相比完全低乙酰化。相比之下，抑制NFATc 1核转位无论是环孢菌素或通过使用原代小鼠成骨细胞与删除钙调磷酸酶b1阻止HDAC 3与骨钙素启动子的近端调控位点。这些初步结果表明，NFATc 1作为骨钙素启动子的转录辅阻遏物可能在HDAC依赖的方式。
We previously reported that the in vivo and in vitro suppression of Nuclear Factor of Activated T Cells (NFAT) signaling increases osteoblast differentiation and bone formation. To investigate the mechanism by which NFATc1 regulates osteoblast differentiation, we established an osteoblast cell line that overexpresses a constitutively active NFATc1 (ca-NFATc1). The activation of NFATc1 significantly inhibits osteoblast differentiation and function, demonstrated by inhibition of alkaline phosphatase activity and mineralization as well as a decrease in gene expression of early and late markers of osteoblast differentiation such as osterix and osteocalcin, respectively. By focusing on the specific role of NFATc1 during late differentiation, we discovered that the inhibition of osteocalcin gene expression by NFATc1 was associated with a repression of the osteocalcin promoter activity, and a decrease in TCF/LEF transactivation. Also, overexpression of NFATc1 completely blocked the decrease in total histone deacetylase (HDAC) activity during osteoblast differentiation and prevented the hyperacetylation of histones H3 and H4. Mechanistically, we show by Chromatin Immunoprecipitation (ChIP) assay that the overexpression of NFATc1 sustains the binding of HDAC3 on the proximal region of the osteocalcin promoter, resulting in complete hypoacetylation of histones H3 and H4 when compared to GFP-expressing osteoblasts. In contrast, the inhibition of NFATc1 nuclear translocation either by cyclosporin or by using primary mouse osteoblasts with deleted calcineurin b1 prevents HDAC3 from associating with the proximal regulatory site of the osteocalcin promoter. These preliminary results suggest that NFATc1 acts as a transcriptional co-repressor of osteocalcin promoter possibly in an HDAC-dependent manner.
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影响因子：
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通讯作者：
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