PML-RARα对BHLHB2基因转录调控的影响

Transcriptional Regulation of BHLHB2 Induced by PML-RARα

本研究探讨异常转录因子PML-RARα对BHLHB2基因的转录调控机制,进一步揭示急性早幼粒细胞性白血病(APL)的致病机理。利用RT-PCR技术研究PML-RARα融合蛋白及ATRA在APL模式细胞株PR9和APL病人来源的NB4细胞中对BHLHB2转录的影响;利用ChIP-PCR技术探讨PML-RARα在体内调控BHLHB2转录的作用方式;通过分析病人样本数据,观察BHLHB2在各种急性髓系白血病(AML)中的表达情况。结果表明,随着PML-RARα融合蛋白的表达升高,BHLHB2的转录受到明显抑制,并且无论在APL模式细胞株PR9还是APL病人来源的NB4细胞中,ATRA均能够解除这种抑制,诱导BHLHB2的表达上调;而在不表达PML-RARα的U937细胞株中,ATRA不能诱导BHLHB2的表达上调。研究结果提示,PML-RARα通过结合于BHLHB2的启动子区域抑制其转录。与其他类型的AML和正常的骨髓细胞相比,BHLHB2在APL中表达较低。结论:BHLHB2是PML-RARα的靶基因,PML-RARα通过与其启动子区域结合对其转录进行负调控。

Objective of this study was to investigate the transcriptional regulation of BHLHB2 gene by the PML-RARα fusion protein in APL cells and reveal the pathogenesis of APL. RT-PCR was performed to detect the expression change of BHLHB2 before and after the induction of PML-RARα in PR9 cells, and its expression level after the treatment of ATRA in PR9 and APL patient derived NB4 cells. Chromatin immunoprecipitation （CHIP） -based PCR was used to analyze whether the BHLHB2 promoter could be bound by PML-RARα in vivo. A large-scale gene expression profile dataset was used to observe the expression pattern of BHLHB2 in AML. The results showed that the expression level of BHLHB2 was significantly reduced with the induction of PML-RARα and ATRA could reverse this inhibition in both PR9 and NB4 cells and increase the expression of BHLHB2. However, the expression of BHLHB2 could not be induced by ATRA in U937 cells which do not express PML-RARα. Mechanism study revealed that PML-RARα could bound to the promoter of BHLHB2 in vivo to regulate the the expression of BHLHB2. It was found that the expression of BHLHB2 was relatively lower in APL as compared with other subtypes of AML and normal bone marrow cells. It is concluded that BHLHB2 is the target of PML-RARα, and the expression of BHLHB2 is inhibited by PML-RARα through binding to its oromoter in APL.