Makorin-1 Control of Telomerase

端粒酶活性和端粒稳态的调控在生长控制中具有重要意义。这项提议的新数据表明，人类端粒酶活性受泛素化调节。具体来说，端粒酶的催化亚基hTERT在翻译后被泛素修饰，并被引导到26S蛋白酶体进行降解。一个特定的E3连接酶基因已被鉴定并克隆自人类。这种连接酶与一个保守的古老基因makorin-1相同，makorin-1是最近发现的一个功能未知的基因家族的创始成员。MKRN1编码一种环锌指蛋白，催化泛素与hTERT的连接。通过TRAP检测，癌细胞中高水平的MKRN1表达导致端粒DNA侵蚀和端粒酶活性降低。为了了解这种hTERT调控的新途径，我们计划了一系列的目标来详细研究MKRN1在癌细胞中过度表达和过低表达的后果。本研究的最终目标是确定癌症治疗干预的新靶点，并探索蛋白酶体途径如何与端粒稳态途径机械交叉。端粒是染色体的物理末端，由重复DNA序列（TTAGGG）加密，并由端粒酶维持。我们有新的证据表明，人类端粒酶是由泛素/蛋白酶体途径调节的，我们已经克隆了一种叫做MKRN1的端粒酶杀手基因。由于大多数肿瘤细胞不适当表达端粒酶，端粒酶失活途径对于设计新的干预癌症的方法具有临床意义。

DESCRIPTION (provided by applicant): SUMMARY Regulation of telomerase activity and telomere homeostasis is fundamentally important in growth control. New data in this proposal suggest that human telomerase activity is regulated by ubiquitylation. Specifically, the catalytic subunit of telomerase, hTERT, is post-translationally modified by ubiquitin and directed to the 26S proteasome for degradation. A specific E3 ligase gene has been identified and cloned from humans. This ligase is identical to a well conserved and ancient gene called makorin-1, the founding member of a recently discovered gene family of unknown function. MKRN1 encodes a RING-zinc finger protein that catalyzes the ligation of ubiquitin to hTERT. High levels of MKRN1 expression in cancer cells lead to telomere DNA erosion and a reduction in telomerase activity as measured by the TRAP assay. In order to understand this new pathway for hTERT regulation, a series of objectives are planned to examine in detail the consequences of over and under-expressing MKRN1 in cancer cells. The ultimate goal of this research is to identify novel targets for therapeutic intervention in cancer and to explore how the proteasome pathway intersects mechanistically with the telomere homeostatic pathway. Telomeres are the physical ends of chromosomes encrypted by a repeat DNA sequence (TTAGGG) and maintained by telomerase. We have new evidence that human telomerase is regulated by the ubiquitin/proteasome pathway and we have cloned a telomerase killer gene called MKRN1. Since most tumor cells inappropriately express telomerase, a telomerase inactivation pathway is of clinical significance in designing new ways to intervene in cancer.