Mitogen-activated Protein Kinase (MAPK)-regulated Interactions between Osterix and Runx2 Are Critical for the Transcriptional Osteogenic Program
Mitogen-activated Protein Kinase (MAPK)-regulated Interactions between Osterix and Runx2 Are Critical for the Transcriptional Osteogenic Program
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DOI：
10.1074/jbc.m114.576793
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发表时间：
2014-09-26
影响因子：
4.8
通讯作者：
Ventura, Francesc
中科院分区：
文献类型：
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作者：
Artigas, Natalia;Urena, Carlos;Ventura, Francesc
转录因子Runx2和OSx(Osterix)是成骨细胞分化和骨形成所必需的。Runx2的表达发生在骨软骨前体细胞确定的早期阶段，随后在成骨细胞成熟期间诱导OSX的表达。我们证明，OSX和Runx2的共同表达导致成骨基因Col1a1、Fmod和Ibsp的协同诱导表达。OSX和Runx2在调节这些启动子的功能上的相互作用是由邻近的Sp1和Runx2 DNA结合位点的增强子区域所介导的。这些增强子可以通过OSX和Runx2与其特定的DNA启动子序列的结合以及它们之间的蛋白质-蛋白质相互作用来形成协同转录复合体。我们还确定了OSX和Runx2之间相互作用所涉及的结构域。这些区域包含OSX和Runx2中已知的被p38和ERK MAPK磷酸化的氨基酸。抑制p38和ERK的活性或它们在OSX或Runx2中已知的磷酸化位点的突变强烈地扰乱了它们的物理相互作用和协同转录效应。总之，我们的结果提供了OSX和Runx2转录合作机制的分子描述，该机制在成骨过程中受到MAPK激活信号的进一步调控。
The transcription factors Runx2 and Osx (Osterix) are required for osteoblast differentiation and bone formation. Runx2 expression occurs at early stages of osteochondroprogenitor determination, followed by Osx induction during osteoblast maturation. We demonstrate that coexpression of Osx and Runx2 leads to cooperative induction of expression of the osteogenic genes Col1a1, Fmod, and Ibsp. Functional interaction of Osx and Runx2 in the regulation of these promoters is mediated by enhancer regions with adjacent Sp1 and Runx2 DNA-binding sites. These enhancers allow formation of a cooperative transcriptional complex, mediated by the binding of Osx and Runx2 to their specific DNA promoter sequences and by the protein-protein interactions between them. We also identified the domains involved in the interaction between Osx and Runx2. These regions contain the amino acids in Osx and Runx2 known to be phosphorylated by p38 and ERK MAPKs. Inhibition of p38 and ERK kinase activities or mutation of their known phosphorylation sites in Osx or Runx2 strongly disrupts their physical interaction and cooperative transcriptional effects. Altogether, our results provide a molecular description of a mechanism for Osx and Runx2 transcriptional cooperation that is subject to further regulation by MAPK-activating signals during osteogenesis.