Securin 與細胞週期調控蛋白質之交互作用能力探討

Abstract

人類Securin蛋白質是一個具有202個胺基酸，無穩定結構的多功能性蛋白質。前人研究顯示，Securin在細胞內扮演的角色有(1) 調控姐妹染色體正常地分離 (2)參與細胞自我修復 (3)調控細胞自我凋零 (4)調節細胞週期的行進以及 (5)調控細胞分化等。由於Securin擁有這樣多重要性的功能，許多的研究也發現，在許多腫瘤細胞中，諸如腦下垂體癌、肺癌、乳癌、大腸癌等等，可發現到securin高度表現的現象。Securin蛋白質有兩種後修飾：分別為磷酸化與泛素化作用。前者目前僅知與細胞分裂調控，以及可能與細胞增生及分化有關聯；後者則與securin的降解作用有關。為了釐清securin與多種細胞週期相關蛋白質之作用及磷酸化對securin的功能之影響，我們利用Erk2酵素將securin磷酸化，以遠西方墨點法探討磷酸化修飾與未修飾的securin，與各個細胞週期調控蛋白質交互作用力的變化。結果顯示，磷酸化後的securin與數種細胞週期調控蛋白質之交互作用能力降低。此外，我們利用電化學感測的方式，探討securin磷酸化對p53結合能力變化。我們發現，磷酸化的securin，亦會因此失去與p53交互作用的能力，因而促使p53被活化而啟動細胞自我凋零的機制。藉由本研究我們更清楚的解析securin在細胞內之功能。

Human securin is an intrinsically disordered, protein with 202 amino acids. Previous studies showed that securin played important roles in separation of sister chromatids, DNA repair, apoptosis, cell cycle progression, and cell differentiation. The overexpression of securin is one of the key issur for cancer development, such as in the case of pituitary tumor, lung cancer, breast cancer, and colon cancer. There are two types of post-translational modification of securin, phosphorylation and ubiquitylation. Securin phosphorylation may participate in the function of cell mitosis, cell proliferation, and cell differentiation, but the details mechanism remain unknown. Ubiquitylation is highly related to the degradation of securin. In order to reveal the binding affinity changes among securin and cell cycles regulatory proteins, securin has been phosphorylated by Erk2 kinases. Meanwhile, six cell cycle related proteins have been cloned and expressed in this study. The binding ability assay has been carried out by far western blot method. Moreover, the binding analysis between specific DNA promoter sequence and p53 has been analysed by impedance spectroscopy (EIS). The results indicated that p53 lost bax promoter binding ability by interacting with securin, but not for the phosphorylated one. In summary, based on study, the intermolecular interaction of securin have been revealed clearly.