Identification of the cyclin D1 gene as a target of activating transcription factor 2 in chondrocytes
Identification of the cyclin D1 gene as a target of activating transcription factor 2 in chondrocytes
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DOI：
10.1073/pnas.96.4.1433
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发表时间：
1999-02-16
影响因子：
11.1
通讯作者：
LuValle, P
中科院分区：
文献类型：
--
作者：
Beier, F;Lee, RJ;LuValle, P
软骨内骨的生长受软骨细胞增殖和分化速率的调节。然而，调节这些过程的细胞内机制知之甚少。最近，显示编码转录因子激活转录因子2（ATF-2）的基因的中断抑制小鼠中软骨细胞的增殖[Reimold，A. M等，（1996）Nature（伦敦）379，262-265]，负责该表型的ATF-2的靶基因仍然未知，在此我们报道细胞周期蛋白D1基因是软骨细胞中ATF-2的直接靶，ATF-2存在于来自软骨形成细胞系的核提取物中，并作为与CRE结合蛋白（CREB）/CRE调节蛋白的复合物结合，与细胞周期蛋白D1启动子中的cAMP反应元件（CRE）连接。细胞周期蛋白D1 CRE的突变导致软骨细胞中启动子活性降低78%。软骨细胞中ATF-2的过表达增强了细胞周期蛋白D1启动子的活性3.5倍。相反，通过CREB和ATF-2的显性负性抑制剂的表达来抑制内源性ATF-2或CREB，通过CRE显著降低了软骨细胞中启动子的活性。此外，ATF-2缺陷小鼠的软骨细胞中细胞周期蛋白D1蛋白的水平大大降低。这些数据确定了细胞周期蛋白D1基因作为软骨细胞中ATF-2的直接靶点，并表明细胞周期蛋白D1的表达减少有助于这些小鼠的软骨发育缺陷。
Endochondral bone growth is regulated by the rates of chondrocyte proliferation and differentiation. However, the intracellular mechanisms regulating these processes are poorly understood. Recently, interruption of the gene encoding the transcription factor activating transcription factor 2 (ATF-2) was shown to inhibit proliferation of chondrocytes in mice [Reimold, A. M,, et al, (1996) Nature (London) 379, 262-265], The target genes of ATF-2 that are responsible for this phenotype remain unknown, Here we report that the cyclin D1 gene is a direct target of ATF-2 in chondrocytes, ATF-2 is present in nuclear extracts from chondrogenic cell lines and binds, as a complex with a CRE-binding protein (CREB)/CRE modulator protein, to the cAMP response element (CRE) in the cyclin D1 promoter. Mutation of the cyclin D1 CRE caused a 78% reduction in the activity of the promoter in chondrocytes. Overexpression of ATF-2 in chondrocytes enhanced activity of the cyclin D1 promoter 3.5-fold. In contrast, inhibition of endogenous ATF-2 or CREB by expression of dominant-negative inhibitors of CREB and ATF-2 significantly reduced the activity of the promoter in chondrocytes through the CRE, In addition, levels of cyclin D1 protein are greatly reduced in the chondrocytes of ATF-2-deficient mice. These data identify the cyclin D1 gene as a direct target of ATF-2 in chondrocytes and suggest that reduced expression of cyclin D1 contributes to the defective cartilage development of these mice.