REGULATION OF BONE CELL GENES BY 1,25-(OH)2 VITAMIN D

对成骨细胞活性的分析是理解 在正常生理和疾病中的骨骼动态平衡，因为 成骨细胞负责合成新骨和刺激 成骨细胞向骨吸收转化。成骨细胞的中心作用与 有各种各样的激素和旁分泌因素影响 成骨细胞活性。1.25-二羟基维生素D3[1，25(OH)2D3]，主要 钙调节激素，直接作用于成骨细胞改变 遗传程序的表达。1，25(OH)2D3如何 调节成骨细胞基因表达将有助于阐明成骨细胞如何 不同的角色受到调节，将成为类固醇如何发挥作用的有用模型 激素受体与其他调节蛋白相互作用，以确定 细胞的表型。2-1，25(OH)2D3对大鼠骨钙素基因的影响 将进行详细的分析。这种基因实际上只在 1，25(OH)2D3对成骨细胞骨钙素基因转录的影响 培养成骨样细胞。将使用克隆基因的转基因 定义必要和充分的DNA序列以授予响应性 到1，25(OH)2D3到骨钙素基因。DNA结合研究，使用细胞 提取物，纯化的受体和基因产生的受体，将是 以确定与1，25(OH)2D3受体结合的DNA序列，这些 结合骨钙素基因表达所需的其他因子，并 定义相关结合蛋白之间的相互作用。这个 其他激素和细胞信使(甲状腺素， 维甲酸、雌激素、糖皮质激素、蛋白质激活因子 激酶C)影响骨钙素基因转录将是系统性的 已评估。可能的相加、协同和拮抗效应将 在特定DNA结合和激活的水平上进行分析 抄写。激素反应转录因子的相互作用 骨骼特异的转录因子也将同样被分析。这个 完整染色质中骨钙素基因的结构将被评估为 定义对DNA酶I高度敏感的调节区。 研究将在对克隆基因的研究和对中国基因的研究之间提供联系 SITE。 因此，该项目的目标是为全面的 了解1，25(OH)2D3等激素对成骨细胞的调控 遗传程序。

An analysis of the activity of osteoblasts is central to an understanding of skeletal homeostasis in normal physiology and in disease, since osteoblasts are responsible for synthesizing new bone and for stimulating osteoblasts to resorb bone. The central role of osteoblasts correlates with the wide variety of hormonal and paracrine factors that influence osteoblast activity. 1.25-dihydroxyvitamin D3 [1,25(OH)2D3], a major calcium-regulating hormone, acts directly on osteoblasts to alter expression of the genetic program. An analysis of how 1,25(OH)2D3 modulates osteoblast gene expression will help clarify how the osteoblast's varying roles are regulated and will serve as a useful model of how steroid hormone receptors interact with other regulatory proteins to determine a cell's phenotype. The effects of 2\1,25(OH)2D3 on the rat osteocalcin gene will be analyzed in detail. This gene is expressed virtually only In osteoblasts; osteocalcin gene transcription is stimulated by 1,25(OH)2D3 in cultured osteoblast-like cells. Transfection of cloned genes will be used to define DNA sequences necessary and sufficient to confer responsiveness to 1,25(OH)2D3 to the osteocalcin gene. DNA binding studies, using cell extracts, purified receptors, and genetically produced receptors, will be performed to define DNA sequences that bind the 1,25(OH)2D3 receptor, those that bind other factors required for osteocalcin gene expression, and to define the interactions between the relevant binding proteins. The possibility that other hormones and cellular messengers (thyroxine, retinoic acid, estrogen, gluccorticoids, factors activated by protein kinase C) affect osteocalcin gene transcription will be systematically evaluated. Possible additive, synergistic, and antagonistic effects will be analyzed at the levels of specific DNA binding and activation of transcription. The interaction of hormone-responsive transcription factors and bone-specific transcription factors will similarly be analyzed. The structure for the osteocalcin gene in intact chromatin will be evaluated to define regulatory regions that are hypersensitive to DNAse I. These studies will provide a link between studied of cloned genes and of genes in situ. This project's goal is thus to build a base for a comprehensive understanding of how 1,25(OH)2D3 and other hormones modulate the osteoblast genetic program.