己糖胺生物合成途径调控组蛋白甲基化酶DOT1L蛋白水平的机制及功能研究

葡萄糖代谢的己糖胺生物合成途径（HBP）提供蛋白质O-GlcNAc修饰的供体，该修饰的异常与肿瘤等疾病密切相关。组蛋白H3K79的甲基化酶DOT1L在MLL融合型白血病中起关键作用。目前对DOT1L受到的调控与葡萄糖代谢之间的关系了解较少。在本研究中，我们发现：HBP显著调节DOT1L的蛋白水平及其下游基因表达；DOT1L可被O-GlcNAc修饰且该修饰可能降低其与E3泛素连接酶TRIM25的相互作用。我们将深入研究：HBP是否通过DOT1L的O-GlcNAc修饰影响其泛素化；TRIM25是否直接调控DOT1L的泛素化并受到DOT1L的O-GlcNAc修饰的影响；MLL融合型白血病中葡萄糖/HBP/TRIM25是否通过DOT1L调控下游HOXA9等基因的表达及细胞的增殖。本研究的成功开展将揭示葡萄糖代谢和组蛋白甲基化之间的一个新联系，并为MLL-融合型白血病的基础研究和治疗提供新的思路。

Hexosamine Biosynthetic Pathway (HBP) of glucose metabolism provides UDP-GlcNAc for protein O-GlcNAcylation. Abnormality in protein O-GlcNAcylation associates with various diseases including tumor. Histone H3K79 methyltransferase DOT1L plays a critical role in MLL-fusion leukemia. Currently little is known regarding the interplay between DOT1L and glucose metabolism. In this study, we found HBP significantly regulated DOT1L protein level and expression of DOT1L downstream genes. We also found that DOT1L could be O-GlcNAcylated which might undermine its interaction with E3 ligase TRIM25. We will further determine whether HBP regulates ubiquitination of DOT1L through its O-GlcNAcylation. We will also clarify whether TRIM25 directly ubiquitinates DOT1L and whether TRIM25 activity on DOT1L is affected by DOT1L O-GlcNAcylaion. Finally we will investigate whether Glucose/HBP/TRIM25 regulates MLL-fusion leukemia cell proliferation and expression of genes such as HOXA9 through DOT1L. This research project will reveal new connection between glucose metabolism and histone lysine methylation, providing novel insights into the mechanism and therapeutics of MLL-fusion leukemia.