异硫氰酸苯己酯诱导Molt-4细胞p15基因去甲基化及机制研究

Phenylhexyl isothiocyanate induces gene p15 demethylation by down-regulating DNA methyltransferases in Molt-4 cells

研究新型组蛋白去乙酰化酶抑制剂异硫氰酸苯己酯(PHI)对急性T淋巴细胞性白血病Molt-4细胞p15基因的去甲基化作用及诱导沉默基因重新表达作用,并进一步探讨其作用机制。应用甲基化特异性聚合酶链反应(MSP)检测PHI作用前后Molt-4细胞株p15基因甲基化状态的变化;半定量逆转录-聚合酶链反应(RT-PCR)检测Molt-4细胞经过PHI处理后DNA甲基转移酶DNMT1、DNMT3A、DNMT3B、p15基因的mRNA的表达变化;用蛋白免疫印迹(Western blotting)检测Molt-4细胞经过PHI处理后的P15蛋白的表达。结果显示,PHI作用于Molt-4细胞5d后,p15基因的甲基化程度减弱,p15基因的异常高甲基化现象被逆转,沉默的p15基因重新表达,p15mRNA、P15蛋白表达增加,并呈浓度依赖性;PHI可下调DNMT1和DNMT3B的mRNA表达(P<0.05),而对DNMT3A的mRNA表达作用不明显(P>0.05)。PHI可能通过抑制DNA甲基转移酶DNMT1和DNMT3B的活性,诱导p15基因产生去甲基化,或者(和)是通过改变p15基因附近组蛋白的乙酰化水平,导致染色体空间结构发生变化,增加转录因子的进入,从而诱导p15基因重新表达。

This study is to investigate the effect of phenylhexyl isothiocyanate （PHI）, which has been proved to be a novel histone deacetylase inhibitor （HDACi） recently, on gene p15 de novo expression in acute leukemia cell line Molt-4, and to further study its potential mechanism. Modified methylation specific PCR （MSP） was used to screen p15-M and p15-U mRNA. DNA methyltransferase1 （DNMT1）, 3A （DNMT3A）, 3B （DNMT3B） and p15 mRNA were measured by RT-PCR. P15 protein was detected by Western blotting. Hypermethylation of gene p15 was reversed and activation transcription of gene p15 in Molt-4 was de novo after 5 days exposure to PHI in a concentration dependent manner. DNMT1 and DNMT3B were inhibited by exposure to PHI for 5 days （P 〈 0.05）. Alteration of DNMT3A was not significant. It is showed that PHI could reverse hypermethylation of gene p15 and transcriptional activation of gene p15 is de novo by PHI. It may result from down-regulating DNA methyltransferases, DNMT1 and DNMT3B, or up-regulating the histone acetylation that allows chromatin unfolding and the accessibility of regulators for transcriptional activation in the p15 promoter.