VIT D AND ESTROGEN RECEPTOR COACTIVATORS IN OSTEOBLASTS

骨质疏松症是一种以低骨量为特征的代谢性骨疾病 以及骨组织的微观结构恶化， 骨脆性增加，骨折风险增加。 两个主要 类固醇激素与阿尔茨海默病有密切联系， 过程是雌激素（E2）和1 α，25-二羟维生素D3 （1，25（OH）2D3）。 E2和1，25（OH）_2D_3的生物学效应是 通过核受体（分别为ER和VDR）介导 其作为配体激活的转录因子发挥作用， 骨细胞中特定基因或基因网络的表达。 然而，这些受体影响的确切机制 转录过程在很大程度上是未知的。 初步 研究中，我们已经分离出一种新的人类cDNA克隆， 62，000 Da核蛋白，选择性地与几种 核受体，包括VDR和ER。 重要的是， 该cDNA克隆在VDR应答基因表达中的共表达 系统显著增强1，25（OH）2D3-/VDR介导的转录。 该克隆已被命名为NCoA-62，即核受体 分子量为62，000 Da的辅活化剂。 长期目标是 建议是了解VDR-和ER-的分子机制， 在骨细胞中介导的基因表达，在短期内， 研究计划的重点是确定NCoA-62的功能作用 维生素D和雌激素调节转录。 我们的假设 NCoA-62是一种桥接蛋白， 启动子结合受体与 转录前起始复合体 为了验证这个假设，我们 提出四个具体目标：1.确定是否涉及NCoA 62 在哺乳动物细胞中ER介导的转录2.鉴定蛋白质 结构域对于NCoA 62共激活因子活性是重要的3.审查 NCoA-62在1，25（OH）2D3和E2介导的 成骨细胞系中的转录4.识别和表征 与NCoA 62相互作用的成骨细胞核蛋白。 这些研究的目的是为了提高我们的理解的基本 维生素D和雌激素依赖性转录的机制 并确定其重要的功能成分 复杂的过程 通过对这种复杂的理解， 在此过程中，将实现合理的治疗策略， 治疗和预防使人衰弱的骨病， 骨质疏松

Osteoporosis is a metabolic bone disorder characterized by low bone mass and microstructural deterioration of bone tissue, culminating in increased bone fragility and increased risk of fracture. Two principle steroid hormones which have strong links to the osteoporotic disease process are estrogen (E2) and 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3). The biological effects of E2 and 1,25(OH)2D3 are mediated through nuclear receptors (the ER and the VDR, respectively) which function as ligand activated transcription factors that control the expression of specific genes or gene networks in bone cells. However, the precise mechanisms through which these receptors influence the transcriptional process are largely unknown. In preliminary studies, we have isolated a novel, human cDNA clone that encodes a 62,000 Da nuclear protein that interacts selectively with several nuclear receptors, including the VDR and the ER. Importantly, coexpression of this cDNA clone in a VDR-responsive gene expression system dramatically augments l,25(OH)2D3-/VDR-mediated transcription. The clone has been designated as NCoA-62, for Nuclear Receptor CoActivator of 62,000 Da molecular mass. The long-term goal of this proposal is to understand the molecular mechanism of VDR- and ER- mediated gene expression in bone cells and in the short-term, this research proposal focuses on determining the functional role of NCoA-62 in vitamin D and estrogen regulated transcription. Our hypothesis states that NCoA-62 is a bridging protein that serves as an important communication link between the promoter-bound receptor and the transcription preinitiation complex. To test this hypothesis, we propose four specific aims that: 1. establish whether NCoA62 is involved in ER-mediated transcription in mammalian cells 2. identify the protein domains that are important for NCoA62 coactivator activity 3. examine the essentiality of NCoA-62 in 1,25(OH)2D3- and E2-mediated transcription in osteoblast cell lines 4. identify and characterize osteoblast nuclear proteins that interact with NCoA62. These studies are designed to improve our understanding of the basic mechanisms involved in vitamin D and estrogen dependent transcription in bone and to identify the important functional components of this complex process. Through an acquired understanding of this complex process, rational therapeutic strategies will be realized in the treatment and prevention of debilitating bone disorders such as osteoporosis.