Telomerase Recruitment Requires both TCAB1 and Cajal Bodies Independently
Telomerase Recruitment Requires both TCAB1 and Cajal Bodies Independently
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DOI：
10.1128/mcb.00379-12
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发表时间：
2012-07-01
影响因子：
5.3
通讯作者：
Bryan, Tracy M.
中科院分区：
文献类型：
--
作者：
Stern, J. Lewis;Zyner, Katherine G.;Bryan, Tracy M.
大多数癌细胞无限生长的能力依赖于端粒酶及其对端粒的募集。在人类细胞中，募集依赖于Cajal小体RNA伴侣TCAB1与端粒酶RNA亚单位(HTR)的结合，也被认为依赖于催化亚单位hTERT的N-末端结构域。我们证明，柯林是Cajal小体的重要结构成分，是内源性端粒酶重新聚集到端粒所必需的，但端粒酶的过度表达可以弥补Cajal小体的缺失。相反，端粒酶的募集对TCAB1的水平很敏感，这不能通过端粒酶的过度表达来挽救。因此，虽然Cajal机构对招募很重要，但TCAB1在这一过程中有独立于这些结构的额外作用。TCAB1本身以端粒酶依赖但Cajal小体不依赖的方式定位于端粒。我们在hTERT中发现了一个点突变，它在很大程度上取消了招募，但不影响端粒酶与TCAB1的关联，表明该区域通过一个独立的机制调节招募。我们的结果表明，端粒酶对端粒的募集有多个独立的要求，TCAB1的功能是直接将端粒酶运输到端粒。
The ability of most cancer cells to grow indefinitely relies on the enzyme telomerase and its recruitment to telomeres. In human cells, recruitment depends on the Cajal body RNA chaperone TCAB1 binding to the RNA subunit of telomerase (hTR) and is also thought to rely on an N-terminal domain of the catalytic subunit, hTERT. We demonstrate that coilin, an essential structural component of Cajal bodies, is required for endogenous telomerase recruitment to telomeres but that overexpression of telomerase can compensate for Cajal body absence. In contrast, recruitment of telomerase was sensitive to levels of TCAB1, and this was not rescued by overexpression of telomerase. Thus, although Cajal bodies are important for recruitment, TCAB1 has an additional role in this process that is independent of these structures. TCAB1 itself localizes to telomeres in a telomerase-dependent but Cajal body-independent manner. We identify a point mutation in hTERT that largely abolishes recruitment yet does not affect association of telomerase with TCAB1, suggesting that this region mediates recruitment by an independent mechanism. Our results demonstrate that telomerase has multiple independent requirements for recruitment to telomeres and that the function of TCAB1 is to directly transport telomerase to telomeres.