KLF4核糖基化和去乙酰化修饰差异在NSCLC中的功能和调控机制研究

Non-small cell lung cancer (NSCLC) is the most common lung carcinoma with high incidence and mortality. The transcriptional factor Krüppel-like factor 4 (KLF4) has been shown to relate with the proliferation and metastasis of lung cancers. However, due to the dual function of KLF4, whether KLF4 plays oncogenic or suppressive roles in lung cancer is still unclear. Our previous work demonstrated that SIRT1 inhibits KLF4 transcription activity through deacetylating KLF4 and that SIRT6 facilitates KLF4 transcription activity via direct catalyzing KLF4 ADP-ribosylation. In addition, we found that the levels of KLF4 vary markedly among different NSCLC cells and exhibit distinct patterns with SIRT6 and SIRT1. In this proposal we aim to investigate further, both in vitro and in vivo, how deacetylation and ADP-ribosylation regulate KLF4 transcriptional activity and function in NSCLC. We will also investigate the potential cross-talks between these modifications and their regulatory effect on KLF4, test if KLF4 expression and its modification are potential early diagnosis markers of NSCLC, and screen potential therapeutic inhibitors on KLF4 modifications.

非小细胞型肺癌(NSCLC)是肺癌中最常见的肿瘤类型。研究表明转录因子KLF4与肺癌的发展及转移关系密切，但是由于KLF4具有促癌和抑癌的双重潜能，KLF4在肺癌中的功能机制仍不清楚。我们前期研究结果发现去乙酰化酶SIRT1通过去除KLF4乙酰化抑制其转录活性，而SIRT6则通过其ADP-核糖基转移酶活性催化KLF4核糖基化修饰并促进KLF4转录活性。并且，KLF4与SIRT6及SIRT1在NSCLC中呈现特殊的表达模式和功能。本项目将以此为基础，在细胞水平和动物水平深入探讨KLF4核糖基化和去乙酰化修饰差异在NSCLC中的功能和调控机制，揭示KLF4不同修饰间可能存在的互作（cross-talk）及其在KLF4转录激活-抑制功能变换中的作用和分子机制；通过分析NSCLC不同时期KLF4修饰水平确认其是否可以作为NSCLC的早期诊断标志物，并在KLF4修饰化抑制剂中初步筛选潜在的靶向药物。

SET1A作为主要的H3K4me3修饰甲基转移酶，主要定位于细胞核。我们的前期研究发现SET1A作为胚胎干细胞核心转录因子Oct4的辅转录激活因子，调控Oct4及其靶基因启动子区域H3K4me3修饰水平，SET1A基因敲除导致小鼠早期胚胎致死。值得注意的是，SET1A作为重要的表观调控因子，其催化底物还包括非组蛋白。本项目研究发现肿瘤微环境因子促进甲基转移酶SET1A催化Hippo信号通路核心效应因子YAP发生甲基化修饰，抑制YAP细胞核输出，导致YAP转录活性持续激活，从而促进细胞增殖和肿瘤发生。