Regulation and Function of hTERT in Human Cells

描述（由申请人提供）：端粒稳态调节哺乳动物细胞中的染色体稳定性和细胞复制寿命。因此，端粒生物学的改变在人类癌症的发病机制中起着关键作用，并可能导致衰老。事实上，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。此外，在以干细胞衰竭为特征的疾病中发现了催化活性所需的端粒酶组分的突变，所述疾病包括先天性角化不良、再生障碍性贫血和特发性肺纤维化的子集。总之，这些端粒酶在维持端粒中起着关键作用，越来越多的证据表明，催化观察暗示端粒酶是癌症和衰老之间的关键联系。 尽管很明显，除了维持端粒的作用外，TERT亚基还参与正常和恶性细胞的生理学。具体而言，在端粒长度不受限制的情况下，TERT的表达驱动肿瘤形成，并以独立于TERC表达的方式改变干细胞功能。在先前的工作中，我们发现，端粒酶在周期性的初级早衰的人成纤维细胞中表达，并且这种低水平的端粒酶表达控制增殖寿命。 在过去的资助期间，我们研究了TERT在正常和恶性哺乳动物细胞中的作用，发现除了在端粒维持中的作用外，TERT还调节整体染色质结构。此外，我们和其他人已经确定了几种新的蛋白质复合物与TERT。在最近的工作中，我们发现TERT与线粒体RNA加工核糖核酸内切酶（RMRP）的RNA组分相互作用，RMRP是一种在遗传性多效性综合征软骨-毛发发育不全中突变的基因。TERT和RMRP形成RNA依赖性RNA聚合酶（RdRP）。这些新的观察结果表明，TERT形成几个不同的酶复合物，并提供了一个基础，了解额外的端粒功能的TERT。 该提案的重点是研究这些新发现的TERT复合物在衰老和癌症中的作用。具体而言，生物化学，遗传学和分子生物学方法将被应用于调查的作用TERT-RMRP RdRP在染色质稳态，衰老和转化，了解TERT-RMRP复合物在正常细胞和组织中的作用，并阐明TERT蛋白复合物在衰老的调节中的功能。这些研究不仅将为各种TERT复合物在衰老和癌症中的作用提供新的见解，而且还将增强我们对异染色质调控的理解。此外，这些研究将为治疗性地操纵这些复合物的策略提供基础。 公共卫生相关性：虽然端粒和端粒酶在衰老和癌症中起着重要作用，但我们对端粒酶组分在衰老和转化中的作用缺乏全面的了解。该提案的重点是破译新发现的TERT复合物在正常和恶性细胞和组织中的作用。这些基于生物化学、细胞和动物的研究不仅将提供对TERT复合物生物学的深入了解，而且将作为开发新型治疗剂的转化研究的基础。

DESCRIPTION (provided by applicant): Telomere homeostasis regulates both chromosomal stability and cell replicative lifespan in mammalian cells. As a consequence, alterations in telomere biology play critical roles in the pathogenesis of human cancer and may contribute to aging. Indeed, studies in both human and animal models indicate that telomeres and telomerase, the reverse transcriptase that maintains telomere structure, serve dual roles in oncogenesis, acting both to suppress and facilitate neoplastic transformation. Moreover, mutations of telomerase components required for catalytic activity, TERT and TERC, are found in diseases characterized by stem cell failure including dyskeratosis congenita, subsets of aplastic anemia and idiopathic pulmonary fibrosis. Taken together, these telomerase plays a key role in maintaining telomeres, accumulating evidence suggests that the catalytic observations implicate telomerase as a critical link between cancer and aging. Although it is clear that subunit of TERT contributes to both normal and malignant cell physiology beyond its role in telomere maintenance. Specifically, expression of TERT drives tumor formation under situations when telomere length is not limiting and alters stem cell function in a manner that is independent of the expression of TERC. In prior work, we found that TERT is expressed in cycling primary pre-senescent human fibroblasts and that this low-level expression of telomerase controls proliferative lifespan. During the past funding period, we have investigated the role of TERT in both normal and malignant mammalian cells and found that in addition to its role in telomere maintenance, TERT regulates overall chromatin structure. Moreover, we and others have identified several novel protein complexes that associate with TERT. In recent work, we have found that TERT interacts with the RNA component of mitochondrial RNA processing endoribonuclease (RMRP), a gene that is mutated in the inherited pleiotropic syndrome Cartilage-Hair Hypoplasia. TERT and RMRP form an RNA dependent RNA polymerase (RdRP). These new observations suggest that TERT forms several distinct enzymatic complexes and provide a foundation to understand extra-telomeric functions of TERT. This proposal focuses on investigating the role of these newly identified TERT complexes in senescence and cancer. Specifically, biochemical, genetic and molecular biological approaches will be applied to investigate the role of the TERT-RMRP RdRP in chromatin homeostasis, senescence and transformation, to understand the roles of TERT-RMRP complexes in normal cells and tissues and to elucidate the function of TERT protein complexes in the regulation of senescence. These studies will not only provide new insights into the roles of various TERT complexes in aging and cancer but will also enhance our understanding of heterochromatin regulation. In addition, these studies will provide a foundation for strategies to manipulate these complexes therapeutically. PUBLIC HEALTH RELEVANCE: Although it is clear that telomeres and telomerase play important roles in aging and cancer, we lack a complete understanding of the roles of telomerase components in senescence and transformation. This proposal focuses on deciphering the role of newly identified TERT complexes in both normal and malignant cells and tissues. These biochemical, cell and animal- based studies will not only provide insight into the biology of TERT complexes but will serve as a foundation for translational studies for the development of novel therapeutic agents.