细胞衰老过程中P53表观遗传学修饰

Epigenetic modifications of P53 during cellular senescence

目的检测体外培养的人胚肺成纤维细胞复制性衰老过程中及过氧化氢诱导细胞早衰阶段P53的表观遗传学修饰。方法荧光定量采用聚合酶链式反应法(PCR)检测P53的mRNA表达,甲基化特异PCR检测启动子区甲基化改变情况,染色质免疫沉淀结合定量PCR检测其组蛋白修饰,包括组蛋白H3,H4乙酰化和H3(Lys4)及H4(Lys20)甲基化修饰。结果细胞复制性衰老过程中,P53的mRNA表达在中年细胞组显著升高,复制性衰老细胞组也升高,早衰组无明显改变;细胞复制性衰老过程中,其启动子区-820 bp^-656 bp甲基化水平随增龄而降低,早衰组降低明显;复制性衰老细胞组及早衰组的组蛋白修饰在启动子区-889 bp^-676 bp以组蛋白H3(Lys4)甲基化修饰为主;-199 bp^-30 bp的修饰,复制性衰老细胞组以组蛋白H3,H4乙酰化修饰为主,早衰组以H4乙酰化,H3K4甲基化修饰为主。结论细胞衰老过程中,P53启动子区组蛋白修饰参与其mRNA表达调控,复制性衰老与早衰存在调控机制的差异。

Objective Epigenetic regulations of P53 were observed during cellular replicative senescence and premature senescence induced by hydrogen peroxide of human embryonic lung fibroblasts （ HEFs）. Methods The mRNA level of P53 was deteeted by Q-PCR. The methylation status in the promoter region was observed by methylation-specifie PCR. The histone modifications were detected by chromatin immunoprecipitation-Q-PCR assay, including acetylation for H3, H4 and methylation for H3（Lys4） and 1-14 （Lys20）. Results In the process of cellular senescence, the mRNA level of P53 increased in both mid-aged and replicative senescent cells, with no change in premature senescence compared with that of young cells. In the promotor region from - 820 bp to - 656 bp, in comparison with that of young cells, the methylation level for P53 decreased gradually with increased population doubling levels. About the main histone modifications, P53 in the region （ - 889 bp - - 676 bp） was H3K4 methylation in both replicative and premature senescence, while P53 in the region （ - 199 bp - - 30 bp） was H3 and H4 acetylation in replicative senescence and H4 aeetylation and H3K4 methylation in premature senescence to activate the transcription. Conclusions The histone modifications take part in regulating the mRNA expression of P53 during cellular senescence and different mechanisms exist between two types of senescence.