Regulation and Function of Telomerase in Human Cells

描述（由申请人提供）：越来越多的证据表明，端粒的维持调节染色体稳定性和细胞复制寿命。此外，端粒生物学在人类癌症的发病机制中起着关键作用，并可能导致衰老。在人类和动物模型中的研究表明，端粒和端粒酶（维持端粒结构的逆转录酶）在肿瘤发生中起双重作用，既抑制又促进肿瘤转化。在人类中，组成型端粒酶表达促进细胞永生化，是人类肿瘤长期生长所需的，并与癌基因表达合作将原代人类细胞转化为致瘤性。这些观察结果支持端粒酶过度表达对癌症发展至关重要的假设，并且抑制端粒酶表达是抑制肿瘤形成的机制。 尽管有这个概念框架，我们缺乏基本的见解调节端粒酶的表达和功能的分子机制。在正常的人类细胞中，端粒随着细胞分裂的连续轮次而缩短，并且永生化与端粒长度的稳定性相关。这些观察结果表明，人类癌细胞实现永生化，在很大程度上，通过端粒酶的非法激活。然而，我们最近发现，限速端粒酶催化亚基，hTERT，表达在循环的原代人成纤维细胞，以前被认为是缺乏端粒酶活性，这种低水平的端粒酶表达控制细胞增殖。由于这些细胞在培养中传代时表现出端粒缩短，这一意想不到的观察结果表明，端粒酶在调节细胞寿命方面发挥着关键作用，而不仅仅是维持端粒长度。 在这个应用程序中，我们建议调查端粒酶稳定性的调节，并使用分子生物学，遗传学和生物化学的方法来了解端粒酶在正常和恶性细胞中的功能作用。研究端粒酶在人类细胞中的这些新功能不仅将增强我们对端粒生物学的理解，而且还将改变我们对端粒酶在癌症和衰老中作用的看法。由于靶向端粒酶的诊断和治疗策略正在开发中，因此确定端粒酶在正常人类细胞生理学中的作用有望为这些方法的潜在特异性和有效性提供重要见解。

DESCRIPTION (provided by applicant): Accumulating evidence indicates that the maintenance of telomeres regulates both chromosomal stability and cell replicative lifespan. In addition, telomere biology plays critical roles in the pathogenesis of human cancer and may contribute to aging. Studies in both human and animal models indicate that telomeres and telomerase, the reverse transcriptase that sustains telomere structure, serve dual roles in oncogenesis, serving both to suppress and facilitate neoplastic transformation. In humans, constitutive telomerase expression facilitates cell immortalization, is required for the long-term growth of human tumors, and cooperates with oncogene expression to transform primary human cells to tumorigenicity. These observations support the hypotheses that telomerase overexpression is critical to cancer development and that repression of telomerase expression serves as a mechanism to suppress tumor formation. Despite this conceptual framework, we lack fundamental insights into the molecular mechanisms that regulate telomerase expression and function. In normal human cells, telomeres shorten with successive rounds of cell division, and immortalization correlates with stabilization of telomere length. These observations suggest that human cancer cells achieve immortalization, in large part, through the illegitimate activation of telomerase. However, we have recently found that the rate-limiting telomerase catalytic subunit, hTERT, is expressed in cycling primary human fibroblasts, previously believed to be devoid of telomerase activity, and that this low-level expression of telomerase controls cell proliferation. Since such cells exhibit telomere shortening with passage in culture, this unexpected observation suggests that telomerase plays critical roles in regulating cell lifespan beyond simply maintaining telomere lengths. In this application, we propose to investigate the regulation of telomerase stability and to use molecular biological, genetic, and biochemical approaches to understand the functional roles of telomerase in both normal and malignant cells. Investigating these new functions of telomerase in human cells will not only enhance our understanding of telomere biology but will also alter our perceptions of the roles of telomerase in cancer and aging. Since diagnostic and therapeutic strategies that target telomerase are under development, determining the role of telomerase in the physiology of normal human cells promises to provide critical insights into the potential specificity and effectiveness of these approaches.