有絲分裂後期經由Aurora磷酸化Cdc13以拮抗端粒酶之活性

Aurora-dependent phosphorylation of Cdc13 antagonizes telomerase recruitment at M phase

蘇祐代(Yu-Tai Su)

指導教授 ： 鄧述諄

國立臺灣大學/醫學院/微生物學研究所/碩士(2011年)

https://doi.org/10.6342/NTU.2011.10236

摘要

在真核生物中，染色體的末端由蛋白質和DNA形成的特殊結構，稱之為端粒。端粒可以保護染色體不受傷害以維持染色體的完整性，也可避免染色體末端和末端融合，另外，還可經由和端粒酶之間的交互作用影響DNA複製是否完全。我們實驗室先前的研究發現，在出芽酵母菌中Cdc13這個結合染色體末端單股DNA的蛋白，在細胞週期的S phase至G2 phase會被三種蛋白質激酶磷酸化，而這個磷酸化Cdc13的動作會進而誘發端粒酶的活性。然而，如何終止這個過程至今仍未有解答。因此，本篇研究內容即探討細胞中是如何減低端粒酶的活性，使整個週期能夠順利的完成，並回到G1 phase。Ipl1/Aurora是一種在M phase具有活性的蛋白質激酶，使用專一性偵測絲胺酸314磷酸根的抗體，發現Ipl1會影響Cdc13中絲胺酸314的磷酸化。在生物體內的表現型分析顯示出將Cdc13中可以被Ipl1磷酸化的序列突變會造成端粒長度方面的異常。這些結果證明Ipl1會影響Cdc13中端粒酶吸引區域的絲胺酸314的磷酸化，進而使端粒酶受到排斥而離開端粒，以藉此不再繼續端粒的複製延長。綜合以上，Cdc13參與了兩種磷酸化調控的機制，先是在S phase晚期時開始正向吸引端粒酶，而後在M phase時則是扮演負向排斥端粒酶的角色。

關鍵字

端粒 ； 磷酸化 ； 端粒酶吸引區域

並列摘要

Telomeres, the protein-DNA structures found at the natural ends of eukaryotic chromosomes, are required to protect chromosomes from degradation and end-to-end fusion and to facilitate their complete replication. Our previous studies discovered that Cdc13 specifically activates telomerase at the late S phase through three kinases, and this recruitment is inactivated at the late M phase. However, the pathway to attenuate telomerase at the M phase remains elusive in the telomere field. I therefore intend to identify the step to antagonize this telomerase recruitment process that allows cells to smoothly proceed to next G1 phase. IPL1 encodes an essential protein kinase whose function is required during the later part of each cell cycle. Here I showed that Ipl1/Aurora-dependent phosphorylation on S314 of Cdc13 is essential for repulsion of the yeast telomerase complex from telomeres. Thus, Cdc13 participates in two phospho-regulatory steps—first positive at the late S phase, and then negative at the M phase.

並列關鍵字

telomere ； phosphorylation ； telomerase-recruitment domain

參考文獻

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