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的稳定性和细胞的复制寿命。此外，端粒生物学在人类癌症的发病机制中起着至关重要的作用，并可能导致衰老。人类和动物模型的研究表明，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，组成端粒酶的表达促进了细胞的永生化，是人类肿瘤长期生长所必需的，并与癌基因的表达合作，将人类原代细胞转化为致瘤性。这些观察结果支持了端粒酶过表达对癌症发展至关重要的假设，并且端粒酶表达的抑制是抑制肿瘤形成的机制。尽管有这个概念框架，我们对调节端粒酶表达和功能的分子机制缺乏基本的认识。在正常的人类细胞中，端粒随着连续的细胞分裂而缩短，而永生化与端粒长度的稳定有关。这些观察结果表明，人类癌细胞实现永生，在很大程度上是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，在循环的原代人成纤维细胞中表达，以前认为是缺乏端粒酶活性的，并且端粒酶的低水平表达控制细胞增殖。由于这些细胞在培养中表现出端粒缩短，这一意想不到的观察表明，端粒酶在调节细胞寿命方面起着关键作用，而不仅仅是维持端粒长度。在这个应用中，我们建议研究端粒酶稳定性的调控，并利用分子生物学，遗传学和生化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，而且将改变我们对端粒酶在癌症和衰老中的作用的认识。由于针对端粒酶的诊断和治疗策略正在开发中，确定端粒酶在正常人类细胞生理中的作用有望为这些方法的潜在特异性和有效性提供关键的见解。

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.