早幼粒细胞白血病-维A酸受体α融合蛋白对LMO2基因转录调控的影响

Effect of promyelocytic leukemia-retinoic acid receptor fusion protein on transcriptional regulation of LMO2

目的:通过研究急性早幼粒细胞白血病(APL)中染色体融合形成的早幼粒细胞白血病-维A酸受体α(PML-RARα)对红系重要转录因子LMO2基因的转录调控机制,揭示APL中红系分化受阻的潜在机制。方法:利用染色质免疫共沉淀结合多聚酶链反应(ChIP-PCR)技术探讨PML-RARα融合蛋白在体内调控LMO2转录的作用方式。利用荧光素酶报告基因实验研究PML-RARα对LMO2启动子活性的影响。利用逆转录(RT)-PCR技术研究PML-RARα在APL模式细胞株PR9细胞中对LMO2转录的影响。通过分析患者样本数据,观察LMO2在各种急性髓系白血病(AML)中的表达情况。结果:PML-RARα异常融合蛋白结合于LMO2的远端启动子区域,对LMO2的转录活性进行抑制,并且这种抑制呈现梯度依赖的方式。随着PML-RARα的表达升高,LMO2的远端转录本转录水平受到明显抑制,表达量下调。与其他类型的AML以及正常骨髓细胞相比,LMO2在APL中表达较低。结论:LMO2是PML-RARα的靶基因,PML-RARα通过结合在其远端启动子区域对其转录进行负调控。

Objective To reveal the potential mechanism of inhibition of erythropoietic differentiation in acute promyelocytie leukemia （APL） by investigating the effect of promyelocytic leukemia-retinoic acid receptor α（PML-RARα） fusion protein in APL cells on transcriptional regulation of LMO2, a critical transcription factor in erythropoiesis. Methods Chromatin immunoprecipitation-based polymerase chain reaction （ChlP-PCR） was used to investigate whether PML-RARα could bind to LMO2 promoter in vivo. Luciferase report assay was performed to examine whether PML-RARα was able to repress the activity of LMO2 promoter. Revers transeription（RT）-PCR was conducted to measure the expression level of LMO2 before and after induction of PML-RARα in PR9 cells. A large-scale gene expression profile dataset was used to analyze the expression pattern of LMO2 in acute myeloid leukemia （AML）. Results PML-RARα could bind to LMO2 distal promoter region in vivo, and the transcription activity of LMO2 promoter was suppressed in a dose-dependent manner. With the elevation of PML-RARα the transcription level of LMO2 distal transcript was significantly inhibited, and the expression level was down-regulated. The expression of LMO2 was lower in APL when compared with other types of AML and normal bone marrow. Conclusions LMO2 was the target gene of PML-RARα and the transcription of LMO2 was down-regulated by PML-RARα through binding to its distal promoter region.