Mechanisms of Telomere Function

描述(申请人提供)：人类端粒由TTAGGG重复序列和多亚单位蛋白质复合体组成，该复合体是复制和保护染色体末端所必需的。Tankyrase 1是一种多聚腺苷二磷酸核糖聚合酶(PARP)，调节端粒上的保护素结构和功能。Tankyrase 1聚(ADP-核糖基)作用于DNA结合亚基TRF1，导致TRF1泛素化和降解，并通过端粒酶延长端粒。在细胞周期的G2期DNA复制后，除了在端粒长度调节中发挥作用外，Tankyrase 1还需要解决姐妹端粒之间的粘连。此外，Tankyrase 1的缺失会导致细胞周期停滞(处于有丝分裂或G1期)，这取决于细胞类型。因此，Tankyrase 1在端粒复制、复制的姊妹端粒的处理和细胞周期进程中起关键作用。Tankyrase 1增加了复杂性，它有一个密切相关的同系物，tankyrase 2(它可能是多余的)，以及多个结合伙伴和随细胞周期变化的亚细胞定位。在这个提案中，我们将首先阐明端粒上的tankyrase 1在正常人类细胞和肿瘤细胞中的功能以及在细胞周期进程中的功能。其次，我们将阐明tankyrase 2的功能，包括与tankyrase 1的冗余和tankyrase在人和小鼠细胞中的非端粒功能。第三，我们将通过表征其结合伙伴和细胞周期中的磷酸化来阐明tankyrase 1的调节和功能。了解tankyrase 1(和2)的功能将有助于深入了解端粒功能的分子基础，此外还可能揭示协调端粒功能和细胞周期进程的潜在联系。由于端粒完整性在衰老和癌症中起着关键作用，从这项工作中获得的见解将与衰老和癌症的临床策略相关。

DESCRIPTION (provided by applicant): Human telomeres are comprised of TTAGGG repeats and a multisubunit protein complex termed shelterin that is required for the replication and protection of chromosome ends. Tankyrase 1 is a poly(ADP-ribose) polymerase (PARP) that regulates shelterin structure and function at telomeres. Tankyrase 1 poly(ADP- ribosyl)ates (PARsylates) the shelterin DNA-binding subunit TRF1, which leads to TRF1 ubiquitination and degradation, and to telomere elongation by telomerase. In addition to its role in telomere length regulation, tankyrase 1 is required after DNA replication in the G2 phase of the cell cycle to resolve cohesion between sister telomeres. Moreover, tankyrase 1 depletion leads to cell cycle arrest (in mitosis or in G1) dependent on the cell type. Thus, tankyrase 1 plays a key role in the replication of telomeres, the processing of replicated sister telomeres and cell cycle progression. Tankyrase 1 has the added complexity that it has a closely related homolog, tankyrase 2 (with which it may be redundant), as well as multiple binding partners and subcellular localizations that vary with the cell cycle. In this proposal we will first, elucidate the function of tankyrase 1 at telomeres and in cell cycle progression in normal human cells and tumor cells. Second, we will elucidate the function of tankyrase 2, including redundancy with tankyrase 1 and non telomere functions of tankyrases in human and mouse cells. And third, we will elucidate the regulation and function of tankyrase 1 by characterizing its binding partners and phosphorylation across the cell cycle. Understanding tankyrase 1 (and 2) function will provide insights into the molecular basis of telomere function and in addition may also reveal underlying connections that coordinate telomere function and cell cycle progression. Since telomere integrity plays a key role in aging and cancer, insights gained from this work will be relevant to clinical strategies in aging and cancer.