Mechanism & Function of Subnuclear Targeting of Transcription Factors in Bone

亚核组织的参数对骨骼发育和成骨细胞至关重要 分化我们的项目最初将Runx 2确定为成骨细胞特异性核基质， 蛋白质NMP 2。我们提出了Runx 2的分子功能是作为一种 支架蛋白，其整合来自多种成骨信号传导途径的调节信号， 修饰染色质结构并支持调控蛋白的组织和组装， 在靶基因启动子上的策略位点和在病灶中的骨架基因表达的机制 核微环境我们鉴定并在结构和功能上表征了一个C- 末端核内运输信号，将Runx因子引导到基因 激活或抑制。最近，我们已经确定Runx 2与有丝分裂相结合， 染色体调节成骨细胞特异性基因表达和核糖体RNA合成 在成骨细胞有丝分裂后即刻。在与项目2和项目3的合作研究中， 项目1现在将采用一套高度综合的实验方法， Runx 2作为一种表观遗传基因调节因子，可以控制细胞命运、谱系定型 和有丝分裂间期的蛋白质合成。我们将确定 废除Runx 2整合Runx 2处成骨信号的能力的后果 亚核结构域，以控制体内骨骼发生，以及成骨细胞成熟和骨- 离体特异性基因表达（特异性目标1）。另外，我们会检查成骨细胞- 相关基因调控程序依赖于（i）Runx 2的亚核靶向， 间期和（ii）Runx 2的表观遗传功能，其维持表型调节记忆 在有丝分裂期间控制骨表型基因以及细胞周期和生长控制基因 在子代细胞中（具体目标2）。此外，我们将评估骨特异性分子 Runx 2通过调节成骨细胞的合成代谢活性， 成骨细胞特异性基因（由RNA聚合酶II转录）和核糖体RNA基因 （由RNA聚合酶I转录）（特异性目标3）。 相关性：介导骨骼基因调控的核内组织的机制 机械为靶向治疗提供了必要的和新的选择。

Parameters of subnuclear organization are critical for skeletal development and osteoblast differentiation. Our program initially identified Runx2 as the osteoblast-specific nuclear matrix protein NMP2. We developed the concept that the molecular function of Runx2 is to operate as a scaffolding protein that integrates regulatory signals from multiple osteogenic signaling pathways by modifying chromatin structure and supporting the organization and assembly of regulatory machinery for skeletal gene expression at strategic sites on target gene promoters and in focal nuclear microenvironments. We identified and structurally as well as functionally characterized a C- terminal intranuclear trafficking signal that directs Runx factors to nuclear domains where genes are activated or suppressed. Recently, we have established that Runx2 is bound to mitotic chromosomes to modulate both osteoblast specific gene expression and ribosomal RNA synthesis in osteoblasts immediately following mitosis. In collaborative studies with Projects 2 and 3, Project 1 will now pursue a highly integrated set of experimental approaches to examine the function of Runx2 as an epigenetic gene regulator that can control cell fate, lineage commitment and protein synthesis during both interphase and mitosis. We will determine the physiological consequences of abrogating the ability of Runx2 to integrate osteogenic signals at Runx2 subnuclear domains to control skeletogenesis in vivo, as well as osteoblast maturation and bone- specific gene expression ex vivo (Specific Aim 1). In addition, we will examine the osteoblast- related gene regulatory programs that depend on (i) subnuclear targeting of Runx2 during interphase and (ii)the epigenetic function of Runx2 that maintains a phenotypic regulatory memory during mitosis to control bone phenotypic genes as well as genes for cell cycle and growth control in progeny cells (Specific Aim 2). Furthermore, we will assess the bone specific molecular mechanisms by which Runx2 controls the anabolic activity of osteoblasts through regulation of osteoblast-specific genes (transcribed by RNA polymerase II) and ribosomal RNA genes (transcribed by RNA polymerase I) (Specific Aim 3). Relevance: Mechanisms that mediate the intranuclear organization of skeletal gene regulatory machinery provide necessary and novel options for targeted therapy.