有丝分裂阻滞期选择性翻译受体Notch2调控细胞行为和命运的机制研究

Blocking the process of cell division to induce apoptosis is a common chemotherapeutic strategy that has been successfully used in clinic for years. It was recently found when treated with clinical concentration of taxol, the majority of cells exit mitosis after arrested for several hours. Then they die, undergo senescence in G1 or enter next cycle subsequently. However, how different cell fates are determined is still unknown. Although both protein synthesis and degradation are critical for behaviors and fates of the arrested cells, little is known about newly-synthesized proteins and their functions in fate determination after mitotic arrest so far. In the pilot study, we performed a ribosome profiling analysis in normal mitotic and mitotic arrested cells to deep sequence all actively translated mRNA. A number of differentially translated genes were identified. We confirmed newly-translated Notch2 receptor during mitotic arrest regulates the survival of the cell in the subsequent G1 phase. In this study, the signaling cascades of Notch2 in the response of anti-mitotic treatment will be explored to further reveal the regulation of mitotic arrest and fate determination thereafter. This study will help us understand the mechanism underlying the efficacy and drug resistant of anti-mitotic agents.

通过抑制细胞分裂来诱导凋亡是临床上常用的肿瘤化疗策略。近年研究发现多数肿瘤细胞在有丝分裂阻滞后并不是在分裂期启动凋亡，而是阻滞一段时间后进入间期，随后有不同的命运：凋亡、衰老或继续增殖。但目前对于细胞命运是如何决定的机制还不清楚。尽管分裂阻滞期蛋白质合成和降解对细胞复杂的行为和命运变化都有重要贡献，但目前对阻滞期新翻译合成的蛋白分子及其作用所知甚少。我们利用核糖体翻译图谱分析技术,对正常分裂期和分裂阻滞期内所有正在翻译的mRNA进行深度测序分析和验证，发现并确认了受体Notch2在分裂阻滞期的翻译显著上调。初步的功能分析证明Notch2确实调控细胞离开分裂阻滞后的行为和存活。我们拟进一步阐明阻滞期选择性翻译Notch2的分子基础及上下游信号，揭示其参与调控细胞存亡的机制，从而对分裂阻滞后细胞的应激与命运决定机理有更深入的认识。这一研究将有助于理解抗分裂化疗药物的作用机理及耐药的原因。

紫杉醇类的化疗药物通过破坏正常的细胞分裂来诱导凋亡，是临床上常用的化疗药物。虽然在过去二十多年取得了很大成功，但是原发和继发性耐药限制了临床治疗效果。在本项目中我们研究了紫杉醇诱导有丝分裂阻滞到细胞在间期命运决定过程中的调控机制。利用核糖体翻译图谱分析技术,我们对正常分裂期和分裂阻滞期内所有正在翻译的mRNA进行深度测序分析和验证，发现并确认了受体NOTCH2在分裂阻滞期的翻译显著上调。功能分析证明NOTCH2确实调控细胞离开分裂阻滞后的行为和存活，并进一步阐明阻滞期选择性翻译NOTCH2可以被环境中巨噬细胞和其他肿瘤细胞表面的JAG1配体所激活，随后转录促进抗凋亡相关P38信号通路，同时促进细胞因子释放，招募更多的肿瘤相关巨噬细胞浸润，进一步激活NOTCH2信号，从而形成正反馈环路，参与调控细胞存活和进展。联合应用紫杉醇和NOTCH信号通路的抑制剂可以协同抑制肿瘤的增殖，降低紫杉醇耐药，达到更好的治疗效果。本研究为深入理解紫杉醇耐药与细胞命运决定提供了新思路，同时为靶向微管的化疗提供了新的预后标记物和新联合治疗方案。

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