BIOCHEMISTRY AND GENETICS OF VITAMIN D RECEPTOR ACTIONS

描述（改编自申请人的摘要）：维生素D受体 (VDR)与维生素D反应元件（VDRE）结合为异二聚体 与类维生素A X受体（RXR）复合，并介导 1，25-二羟维生素D3 [1，25（OH）2D3]对基因表达的影响。 是 众所周知，额外的核蛋白，称为受体或 核辅助因子，是高亲和力结合所需的， VDRE。 主要研究者使用酵母双杂交系统克隆了 编码VDR相互作用蛋白的cDNA，其中两个在缺乏 在1，25（OH）2D3存在下的9个。 她假设， 从酵母双杂交系统获得的维生素D相互作用蛋白 是1，25（OH）2D3介导的基因调控的转录因子。 在 为了支持这一假设，她发现其中一种，人类类固醇 受体辅激活因子-1（SRC-1），一种已知的用于其它转录因子的转录因子， 类固醇激素以配体依赖性方式与VDR相互作用， 通过β-半乳糖苷酶生产显示。 VDR和SRC-1的相互作用 在1，25（OH）2D3的生理浓度下放置。 缺失突变 VDR的分析确定，配体依赖性激活结构域 （AF-2）是与SRC-1相互作用所必需的， SRC-1的缺失-突变分析表明，27个氨基酸是 需要与VDR交互。 此外，反义研究表明， SRC-1是刺激碱性磷酸酶产生所必需的， 人骨肉瘤细胞对1，25（OH）2D3的反应。 校长 研究人员建议扩展这些研究，以调查是否和 SRC-1和其他假定因子在1，25（OH）2D3中的参与程度 介导的基因调控 预计这些结果将提供重要的 关于1，25（OH）2D3介导效应的分子生物学的新信息 对细胞功能的影响。

DESCRIPTION (Adapted from the Applicant's Abstract): The vitamin D receptor (VDR) binds to the vitamin D response element (VDRE) as a heterodimeric complex with the retinoid X receptor (RXR) and mediates the effects of 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] on gene expression. It is well-established that additional nuclear proteins, termed receptor or nuclear auxiliary factors, are required for high affinity binding to the VDREs. The principal investigator used a yeast two-hybrid system to clone cDNAs which code for VDR-interacting proteins, two of them in the absence of 1,25(OH)2D3 and nine in the presence of 1,25(OH)2D3. She hypothesizes that the vitamin D interacting proteins obtained from the yeast two-hybrid system are transcription factors for 1,25(OH)2D3 mediated gene regulation. In support of this hypothesis, she found that one of them, human steroid receptor coactivator-1 (SRC-1), a known transcription factor for other steroid hormones, interacts with the VDR in a ligand-dependent manner as shown by (-galactosidase production. Interaction of VDR and SRC-1 takes place at physiologic concentrations of 1,25(OH)2D3. Deletion-mutation analysis of the VDR established that the ligand-dependent activation domain (AF-2) of the receptor is required for interaction with SRC-1 and deletion-mutation analysis of SRC-1 demonstrated that 27 amino acids are required for interaction with the VDR. Further, antisense studies indicate that SRC-1 is required for stimulation of alkaline phosphatase production by human osteosarcoma cells in response to 1,25(OH)2D3. The principal investigator proposes to extend these studies to investigate whether and to what extent SRC-1 and other putative factors are involved in 1,25(OH)2D3 mediated gene regulation. The results are predicted to provide important new information about the molecular biology of 1,25(OH)2D3-mediated effects on cellular function.