Abstract
摘要:細胞依固定順序來複製的循環過程稱為細胞週期。我們過去的研究主要著重在細胞週期中的Sphase,而M phase是關鍵的時期,它決定了細胞中的遺傳物質如何均勻分配到兩個子代中,Cdk/Cdc14的比例決定了受質磷酸化的狀態及操控了M phase動作的順序和時間,因此了解M phase中細胞週期Cdc14如何調控可釐清細胞如何維持genome的穩定。我們最近的研究中指出,Cdc13在S phase後期經由被Cdk1、Tel1與Mec1磷酸化而活化端粒酵素。我們進一步想探討在M phase中細胞如何做負向的調控來停止端粒酵素的活化。由於Cdc14是M phase中後期最重要的去磷酸酶,因此我們推論應是由Cdc14參與Cdc13的負向調控。但進一步研究之後發現,主要參與去除Cdc13磷酸根的去磷酸酶並非Cdc14,而是Pph22。研究過程中我們意外發現部分參與細胞分裂的蛋白可能是由Cdc14執行去磷酸化。已知Cdc14會活化APC,進而降解參與M phase的cyclin,所以Cdc14是調控細胞離開M phase最重要的去磷酸酶。此外,細胞在進行細胞質分裂時需要Cdc14的參與,但究竟是哪些進行細胞分裂及細胞質分裂所需的蛋白是由Cdc14去磷酸化仍未知,因此我們計畫找出所有在細胞分裂及細胞質分裂時被Cdc14去磷酸化的蛋白質及這些動作的生物功能。我們與中研院化學所陳玉如研究員合作,利用蛋白質譜分析技術發現了許多蛋白可能是由Cdc14執行去磷酸化的動作,其中Smc4及Bud3是參與細胞分裂及細胞質分裂的重要蛋白。過去幾年我們實驗室研究細胞週期中蛋白質的轉譯後修飾如何調控訊息傳遞,因此已建構好了許多研究蛋白質修飾與功能的方法,這些將用來了解可能受Cdc14所調控的重要細胞分裂及細胞質分裂的蛋白質在訊息傳遞所扮演的角色。Consensus Cdc14結合區域也將被定出。所有生物體都是經由一連串細胞分裂的過程而形成的,藉由研究細胞調控細胞分裂的機制可對胚胎的發育、腫瘤不受限的分裂以及細胞如何保持genome的穩定性有進一步的了解。經此計畫,可以增加我們對Cdc14參與調控細胞週期分子機制的認識。在細胞癌化過程中,細胞週期不受控制是一個很重要的步驟,我們預期在這次的研究中可了解癌細胞調控細胞週期相關的知識,進而可在癌症治療上提供有效的貢獻。
Abstract: All cells duplicate by a fixed sequence called cell cycle. Our previous research focused on the S phase of cell cycle. M phase of cell cycle is critical for cells to equally distribute genetic materials generated from the S phase into two daughters. The Cdk/Cdc14 ratio determines the substrate phosphorylation status and operates the order and timing of mitosis. Understanding how Cdc14-mediated events of the cell cycle are ordered at the M phase is also related to genome maintenance.We recently demonstrated that Cdc13 specifically activates telomerase at the late S phase through the kinases Cdk1, Tel1, and Mec1, and this recruitment is abolished at the late M phase. We intend to identify the mechanism to abrogate this process. Cdc14 was our original candidate for this action because it is the most important phosphatase at the late M phase. Further studies found that Cdc14 is dispensable for dephosphorylation of Cdc13 but Pph22 is the phosphatase to remove the phosphorylations on Cdc13 at the M phase. Accidentally, during the course of this study, we identified that Cdc14 may works on several unidentified targets. Cdc14 was known to be the most critical phosphatase to allow cells to exit from the M phase. It activates APC to degrade M phase cyclin. Additionally, Cdc14 is required for cytokinesis. However, the real targets of Cdc14 for mitosis and cytokinesis remain elusive. We therefore plan to identify all Cdc14 substrates and their biological functions for mitosis and cytokinesis.Under the collaboration with Dr. Yu-Ju Chen at Institute of Chemistry in Academia Sinica, multiple potential Cdc14 substrates were identified by quantitative mass spectrometry analysis. Wet lab approach has allowed us to confirm that one mitosis and one cytokinesis essential components, Smc4 and Bud3, respectively, are potential substrates of Cdc14. Our lab has studied posttranslational modifications in cell cycle signals for many years. Standard approach to study protein modifications and functions in signal transduction will be used to characterize potential substrates of Cdc14 in mitosis and cytokinesis. The consensus Cdc14 binding motif on substrates will also be determined.All living organisms are descended by a series of cell division. Understanding how cells regulate cell division is crucial to understand embryological development, unlimited tumor division, or how cells preserve genomic integrity. Accomplishment of this project will advance our knowledge on molecular mechanisms of Cdc14-mediated controls in cell cycle regulation. Uncontrolled cell cycle progression is a critical step in tumorgenesis. Therefore, the anticipated results from this study will be relevant to how to regulate cell cycle in cancer cells and these findings will provide significant contributions on the cancer treatment.
Keyword(s)
細胞週期
Cdc14
去磷酸化酵素
細胞分裂
細胞質分裂
Cell Cycle
Cdc14
Phosphatase
Mitosis
Cytokinesis