人胚肺成纤维细胞衰老过程中Foxa2启动子区组蛋白修饰变化

Alterations of histone modifications for Foxa2 promoter during cellular senescence of human embryonic pulmonary fibroblast cells

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Foxa2启动子区的组蛋白修饰变化。方法按传代情况将人胚肺成纤维细胞分为年轻细胞(22 population doubling levels,22PDL)组、中年细胞(35PDL)组、复制性衰老细胞(49PDL)组和氧化应激诱导的早衰细胞(premature senescence,PS)组。采用荧光定量PCR检测Foxa2的mRNA表达水平,染色质免疫沉淀方法检测其启动子区IP1(-740 bp^-596 bp)、IP2(-187 bp^+84 bp)的组蛋白修饰,包括组蛋白H3、H4乙酰化及H3(Lys4)、H4(Lys20)甲基化修饰。结果与年轻细胞组比较,复制性衰老细胞组和早衰组人胚肺成纤维细胞Foxa2 mRNA表达水平均降低,差异有统计学意义(P<0.05),中年细胞组无明显变化。在Foxa2 IP1启动子区,衰老的细胞具有降低的H3组蛋白乙酰化和增加的H4(Lys20)甲基化修饰;在IP2启动子区,衰老的细胞具有降低的H3(Lys4)甲基化修饰特征。结论在细胞衰老过程中,Foxa2启动子区特异的组蛋白修饰参与调控其mRNA表达水平。

Objective To detect the aherations of histone modifications for Foxa2 promoter during cellular replicative senescence and premature senescence induced by hydrogen peroxide （H202 ） of human embryonic lung fibroblasts （HEFs） in vitro. Methods The HEFs were divided into young cells （22 population doubling levels, 22PDL）, midaged ceils （35PDL） and replicative senescent cells （49PDL） and premature senescent cells induced by H202 （premature senescence, PS） according to the age definition in cell culture. The mRNA level of Foxa2 was performed by RT-Q-PCR. The histone modifications in the promoter of IP1 （ - 777 bp - - 478 bp） and IP2 （ -187 bp ~ ＋ 84 bp） for Foxa2 were detected by chromatin immunoprecipitation,including acetylation for H3, H4 and methylation for H3 （Lys4）, H4（Lys20）. Results The mRNA level of Foxa2 of HEFs decreased in both replicative senescent cells and premature senescent cells with statistical significant difference （P 〈 0. 05） compared with that of young ceils, while it had no change in midaged cells. In the promoter of Foxa2 IP1, the senescent cells had decreased histone H3 acetylation and increased histone H4 （Lys20） methylation. In the region of IP2,the main histone modification was reduced H3（Lys4） methylation for senescent cells. Conclusion The histone modifications in the promoter region for Foxa2 take part in regulating its mRNA expression during cellular senescence.