Telomere Formation, Sites and Intermediates, During Macronuclear Development of Oxytricha Trifallax

尖毛虫大核发育过程中端粒的形成、位点和中间体

• 批准号: 0110952
• 负责人: Glenn Herrick
• 金额: $ 10万
• 依托单位: University of Utah
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-08-15 至 2002-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0110952&HistoricalAwards=false
• 关键词: Telomere; Formation; Sites; Intermediates; During

A new technique allows rapid and precise mapping of telomere addition sites (TASs) at chromosome ends of the hypotrichous ciliate macronucleus. The macronucleus is carved developmentally from a copy of the cell's gremlin nucleus, involving the generation of 40,000 new telomeres, following the breakage of chromatids of polytenized germline chromosomes, creating chromosomes with just one or a few genes each. Some chromosomes are created using exactly the same TAS pair (called "fixed TASs"), but others are generated by alternative processing. In this case, some chromatids escape breakage altogether and use a heterogeneous set of TASs in a region dictated by cis-acting sequences (called "mixed" TASs). One hypothesis of how this may work is the "hesitant cutter" hypothesis, whereby the TAS spectrum results from the action of a loose complex of the chromatid cutter and enzyme, telomerase. This model suggests that the region is anchored by a binding site ("CBS") for the complex and a relatively poor cut site, such that the cutter is slow to cut; meanwhile the telomerase dissociates, the cut is made, the end left unprotected to nuclease erosion. The nuclease could then proceed through the 3' strand until it pauses under the influence of a cis-acting pause site, often at dT in a string of dTs. This could allow telomerase to act when the erosion is paused. Mapping TASs in mixed regions will allow the uncovering of three types of cis-acting sequences: the CBS, cut, and pause sites. Numerous allelic variants of TAS regions will be so mapped, refining the effective site sequences. In addition, fixed TASs will be mapped to allow the refinement of a consensus site already identified, 3' TAY (Y=purine). This project will help illuminate the processes of chromosome breakage, telomere formation and the action of telomerase. Basic understanding of these processes will be key to understanding cellular senescence.

一种新的技术可以快速而精确地定位下毛状纤毛虫大核染色体末端的端粒添加位点(TASS)。大核是从细胞的小精灵核的副本发育而来的，涉及到4万个新的端粒的生成，在多角化生殖系染色体的染色单体断裂之后，创造出每个染色体只有一个或几个基因的染色体。一些染色体是使用完全相同的TAS对(称为“固定TASS”)产生的，但另一些染色体是通过替代处理产生的。在这种情况下，一些染色单体完全逃避断裂，并在由顺式作用序列决定的区域使用一组不同种类的TASS(称为“混合”TASS)。其中一个假说是“迟疑切割者”假说，根据该假说，TAS光谱是染色单体切割者和端粒酶的松散复合体作用的结果。这个模型认为，该区域由复合体的结合部位(“CBS”)和相对较差的切割部位锚定，因此切割速度较慢；同时，端粒酶解离，切割完成，末端没有受到核酸酶侵蚀的保护。然后，核酸酶可以穿过3‘链，直到它在顺式作用的停顿位点的影响下暂停，通常是在一串DTS中的DT。这可能会让端粒酶在侵蚀暂停时发挥作用。在混合区域作图TASS将允许发现三种类型的顺式作用序列：CBS、CUT和PAUSE位点。许多TAS区域的等位基因变异将被如此定位，从而提炼出有效的位点序列。此外，还将绘制固定的TASS图，以精炼已确定的共识位点3‘Tay(Y=嘌呤)。这个项目将有助于阐明染色体断裂、端粒形成和端粒酶的作用过程。对这些过程的基本了解将是理解细胞衰老的关键。