Mechanisms of Estrogen Repression of TNF-a Transcription

雌激素抑制 TNF-a 转录的机制

基本信息

批准号：
6505469
负责人：
DALE C LEITMAN
金额：
$ 15.05万
依托单位：
UNIVERSITY OF CALIFORNIA, SAN FRANCISCO
依托单位国家：
美国
项目类别：
财政年份：
2002
资助国家：
美国
起止时间：
2002-09-01 至 2004-08-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Osteoporosis is one of the leading causes of mortality and disability in older women. Osteoporosis causes 68,000 deaths per year, which is equivalent to the number of deaths from breast cancer and all gynecological cancers combined. One of the most effective strategies to prevent osteoporosis is to replace estrogen at the onset of menopause. Unfortunately, prolonged treatment with estrogen leads to adverse effects, including an increased incidence of breast and endometrial cancer. Clearly, estrogens that retain their beneficial effects on bone, but do not elicit a proliferative effect on breast or endometrial cells, have the potential to become first-line drugs to prevent osteoporosis. One approach to discover safer and more selective estrogens is to dissect the molecular mechanisms whereby estrogens activate and repress gene transcription. In contrast to transcriptional activation, very little is known about the mechanisms of repression. We studied how estrogens and phytoestrogens repress the tumor necrosis factor (TNF-alpha) promoter, because TNF-a causes osteoporosis by stimulating osteoclasts to resorb bone. Based on these studies, we hypothesized that estrogen receptor (ERbeta) is more effective than ERalpha at repressing gene transcription, and that the activation function-2 surface of ERs and coactivator proteins are required for estradiol-mediated repression. Whereas these findings are novel and important, their interpretation is limited, because they were done with the TNF-alpha promoter linked to reporter genes in transient transfected cells. The goals of this proposal are to extend these observations to the native TNF-alpha gene, and to further probe the basic molecular mechanisms whereby ERs repress gene transcription. In this proposal we will use chromatin immunoprecipitation assays to characterize the protein-protein interactions that occur at the native TNF-alpha promoter between estrogen receptors, transcription factors, such as c-jun and NFKB, and p160 and p300 coregulatory proteins in bone cells that are stably transfected with ERalpha or ERbeta controlled by a tetracycline-inducible promoter. We hypothesize that identifying the proteins involved in repression, and determining how these factors interact with each other is key to developing repression-selective estrogens. We believe that repression-selective estrogens have the potential to become first-line drugs for preventing osteoporosis, because we hypothesize that these estrogens will prevent osteoporosis, but will not promote breast or endometrial cancer.

描述（由申请人提供）：骨质疏松症是老年妇女死亡率和残疾的主要原因之一。骨质疏松症每年导致68,000人死亡，这相当于乳腺癌和所有妇科癌症的死亡人数。预防骨质疏松症的最有效策略之一是在更年期开始时取代雌激素。不幸的是，雌激素长期治疗会导致不良反应，包括乳腺癌和子宫内膜癌的发生率增加。显然，保留其对骨骼的有益作用但不会引起对乳腺或子宫内膜细胞的增殖作用的雌激素有可能成为一线药物以防止骨质疏松症。一种发现更安全，更具选择性雌激素的方法是剖析分子机制，从而激活和抑制基因转录。与转录激活相反，关于抑制机制知之甚少。我们研究了雌激素和植物雌激素如何抑制肿瘤坏死因子（TNF-Alpha）启动子，因为TNF-A通过刺激整骨细胞骨吸收骨骼会引起骨质疏松症。基于这些研究，我们假设雌激素受体（ERBETA）在抑制基因转录时比Eralpha更有效，并且雌二醇介导的抑制作用需要ERS和共激活蛋白的激活功能-2表面。尽管这些发现是新颖而重要的，但它们的解释是有限的，因为它们是用与瞬时转染细胞中的报告基因相关的TNF-Alpha启动子完成的。该提案的目标是将这些观察结果扩展到天然TNF-Alpha基因，并进一步探测基本的分子机制，从而使ERS抑制基因转录。在这项提案中，我们将使用染色质免疫沉淀测定法来表征雌激素受体之间在天然TNF-Alpha启动子之间发生的蛋白质 - 蛋白质相互作用，转录因子（例如C-JUN和NFKB），以及p160和p160和p300核心细胞中通过Eralliber-Eralpha或ERBETA的骨细胞中的p300核心蛋白。我们假设识别涉及抑制作用的蛋白质，并确定这些因素如何相互作用是发展抑制选择性雌激素的关键。我们认为，抑制选择性雌激素有可能成为预防骨质疏松症的一线药物，因为我们假设这些雌激素会预防骨质疏松症，但不会促进乳腺癌或子宫内膜癌。