Regulation of the p53 gene during osteoblast differentiation.

描述（由申请人提供）：该项目的长期目标是研究p53在成骨细胞分化中的作用，成骨细胞分化是骨形成的核心过程。在我们对骨肉瘤的研究中，我们已经表明p53的功能丧失占主导地位，将野生型p53基因替换到这些细胞中不仅会抑制生长，而且会诱导成骨细胞分化。我们认为，p53提供了正确的内部环境的分化因素，从几个来源的输入，由于其参与细胞途径，如凋亡和细胞周期停滞。因此，所提出的实验旨在了解：a）在成骨细胞分化过程中p53是如何调节的。B）允许维持p53表达的调节类型。c）允许表达骨特异性靶标的p53介导的调节的类型。研究的重点将是：a）。探讨p53在成骨细胞分化过程中的调控作用。我们推测，p53在分化过程中的调节是转录的，不像DNA损伤和应激，蛋白质是稳定的。我们将确认其在体外骨分化过程中的激活机制，定义在分化过程中p53发生的翻译后变化，并证明其通过骨特异性试剂的调节。B）.我们假设p53在成骨细胞分化中的作用是由其与其他对骨分化有影响的调节蛋白结合的能力介导的。我们假设这是默认的途径，当受到干扰时，激活细胞周期停滞或凋亡。我们将通过研究p300在成骨细胞分化中的作用来证明这一点。我们还将确定在分化过程中p53与其他调节蛋白的相关性，以及p53和其他蛋白对p300的竞争是否决定了生长和分化之间的平衡。c）p53诱导基因的靶点。虽然许多被鉴定为p53靶点的基因在骨中具有重要作用，但尚不清楚它们在分化过程中是否以p53调节的方式起作用。我们将研究已被确定为具有p53反应元件的靶点，以确定它们在体外骨分化过程中是否经历p53依赖性调节。我们预计，拟议的研究将产生有价值的新数据，揭示更多的p53蛋白的生理作用，并推进我们的知识负责成骨细胞分化的机制。更好地理解细胞生物学的这一基本方面也可能导致涉及骨骼和癌症的疾病的额外益处。所产生的信息将使我们能够更好地了解p53在原发性骨肉瘤中的丢失，以及它在具有在骨中形成成骨细胞病变倾向的晚期前列腺癌中的存在，以及它在骨破坏（类风湿性关节炎）条件下的突变。研究p53在成骨细胞分化中的作用将更好地理解基础细胞生物学的这一方面，也可能在治疗骨和癌症疾病方面带来额外的好处。

DESCRIPTION (provided by applicant): The long-term goal of the project is to investigate the role of p53 in osteoblast differentiation, a process central to bone formation. In our studies with osteosarcomas, we have shown that functional loss of p53 predominates, and replacing the wild type p53 gene into these cells not only results in suppression of growth, but in the induction of osteoblast differentiation. We propose that p53 provides the right internal environment for differentiation by factoring the input from several sources, due to its involvement in cellular pathways like apoptosis and cell cycle arrest. The proposed experiments are therefore designed to understand: a) how p53 is regulated during osteoblast differentiation. b) The type of regulation that allows the maintenance of p53 expression. c) The type of p53 mediated regulation that allows for expression of bone specific targets. The focus of the research will be: a). To identify p53 regulation during osteoblast differentiation. We hypothesize that p53 regulation during differentiation is transcriptional unlike DNA damage and stress where the protein is stabilized. We will confirm its mechanism of activation during in vitro bone differentiation, define post-translational changes that occur to p53 during differentiation and also demonstrate its regulation by bone specific agents. b).We hypothesize that p53's role in osteoblast differentiation is mediated by its ability to associate with other regulatory proteins that have an effect on bone differentiation. We hypothesize that this is the default pathway which when perturbed activates either cell cycle arrest or apoptosis. We will demonstrate this by studying the role of p300 in osteoblast differentiation. We will also determine association of p53 with other regulatory proteins during differentiation and if competition for p300 by p53 and other proteins determine the balance between growth and differentiation. c).Validate targets of p53 inducible genes. While a number of genes identified as p53 targets have important roles in bone, it is not known if they function in a p53 regulated manner during differentiation. We will study targets that have been identified to have p53 response elements to determine if they undergo p53 dependent regulation during in vitro bone differentiation. We anticipate that the proposed studies will generate valuable new data, shed more light on the physiological role of the p53 protein, and advance our knowledge of the mechanisms responsible for osteoblast cell differentiation. A better understanding of this basic aspect of cell biology could also potentially lead to additional benefits in diseases involving bone and cancer. The information generated would allow us to better understand p53's loss in primary osteosarcomas and its presence in advanced prostate cancers with propensity to form osteoblastic lesions in bone, and its mutations in conditions of bone destruction (rheumatoid arthritis). Investigation into the role of p53 in osteoblast differentiation will provide a better understanding of this aspect of basic cell biology and could also potentially lead to additional benefits in treating diseases involving bone and cancer.