Modulation of Mouse RANKL Gene Expression by Runx2 and Vitamin D3
Modulation of Mouse RANKL Gene Expression by Runx2 and Vitamin D3
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DOI：
10.1002/jcb.21929
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发表时间：
2008-12-01
影响因子：
4
通讯作者：
Kitazawa, Sohei
中科院分区：
文献类型：
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作者：
Kitazawa, Riko;Mori, Kiyoshi;Kitazawa, Sohei
核因子-kappa B受体激活剂配体(RANKL)的表达受促骨激素如甲状旁腺素和1α，25-二羟基维生素D-3(1，25(OH)(2)D-3)的调节。Runx2是成骨细胞分化的主要基因，也通过调节RANKL基因来调节破骨细胞的形成。为了阐明Runx2和1，25(OH)(2)D-3调节RANKL表达的机制，我们利用正常(ST2)和Runx2缺陷小鼠(RD-C6)成骨细胞系，研究了Runx2对染色质结构和近端结合部位的作用。Rd-C6细胞在稳态时RANKL的表达高于ST2细胞，但1，25(OH)(2)D-3处理细胞使其在ST2细胞中增加20倍，而在RD-C6细胞中仅增加1.8倍。RANKL 2kb启动子的瞬时转染、Runx2在ST2中的敲除以及Runx2在RD-C6中的强制表达都证实了Runx2使RANKL基因的稳定表达处于较低水平，但对1，25(OH)(2)D-3的转录活性增强有积极作用。此外，用芯片技术对ST2和RD-C6中碱性启动子上游40kb区域的乙酰化状态进行了评估，结果表明，即使在稳定状态下，RD-C6中也检测到H3和H4的历史乙酰化，而在ST2中只检测到1，25(OH)(2)D-3。在稳定状态下，Runx2可能通过浓缩染色质结构抑制RANKL基因的转录，但当Runx2近端可达时，Runx2对1，25(OH)(2)D-3诱导的RANKL转录有正向作用。因此，RANKL在基质/成骨细胞中的表达受到1，25(OH)(2)D-3的强烈调控，后者在两个不同的水平上反式激活该基因。J.细胞。生物化学。105：1289-1297,2008。(C)2008年Wiley-Liss，Inc.
The expression of receptor activator of nuclear factor-kappa B ligand (RANKL) is regulated by bone-seeking hormones such as PTH and 1 alpha,25-dihydroxyvitamin D-3 (1,25(OH)(2)D-3). Runx2, a master gene for osteoblastic differentiation, also modulates osteoclastogenesis by regulating the RANKL gene. To elucidate the mechanism whereby runx2 and 1,25(OH)(2)D-3 regulate RANKL expression, we studied the function of runx2 on the chromatin structure and on the proximal binding sites using osteoblastic cell lines derived from normal (ST2) and runx2-deficient mice (RD-C6). Although the expression of RANKL in the steady-state was higher in RD-C6 than in ST2, 1,25(OH)(2)D-3-treatment of the cells increased it 20-fold in ST2 but only 1.8-fold in RD-C6. Transient transfection studies with proximal RANKL 2kb promoter, runx2 knock-down in ST2, and forced expression of runx2 in RD-C6 all confirmed that runx2 set the steady-state expression of the RANKL gene at a low level, but exerted a positive effect on enhanced transcriptional activity in response to 1,25(OH)(2)D-3. Also, assessment of the acetylation status of the area spanning 40 kb upstream of the basic promoter in ST2 and RD-C6 by ChIP assay revealed that whereas H3 and H4 historic acetylation was detected even in the steady-state in RD-C6, it was detected only with 1,25(OH)(2)D-3 in ST2. In the steady-state, runx2 may suppress RANKL gene by condensing the chromatin structure; however, it exerts a positive effect on 1,25(OH)(2)D-3-induced RANKL transcription when the proximal runx2 sites are accessible. Thus, RANKL expression in stromal/osteoblastic cells is keenly regulated by 1,25(OH)(2)D-3 which transactivates the gene at two different levels. J. Cell. Biochem. 105: 1289-1297, 2008. (c) 2008 Wiley-Liss, Inc.