Zhang Wenjuan, Hu Dalin, Ji Weidong, Yang Linqing, Yang Jianping, Yuan Jianhui, Xuan Aiguo, Zou Fei, Zhuang Zhixiong
Department of Toxicology, School of Public Health and Tropical Medicine, Southern Medical University , Guangzhou , P. R. China.
Free Radic Res. 2014 May;48(5):550-9. doi: 10.3109/10715762.2014.893580. Epub 2014 Mar 10.
Histone modifications are major post-translational mechanisms responsible for regulation of gene transcription involved in cellular senescence. By using immunofluorescence and Western blot, we showed that the global acetylated levels of histone H3 and H4 were significantly reduced in both replicative and premature senescence of human embryonic lung fibroblasts. However the whole trimethylated level of histone H4 lysine 20 was higher in senescent cells. The alterations in the mRNA and protein levels of histone acetyltransferases (HATs), histone methyltransferase (HMT), and histone deacetylases (HDACs) indicate that differential expression exists between replicative and premature senescent cells. Meanwhile, the reduced activity of HDACs was accompanied by cellular senescence. By employing the quantitative chromatin immunoprecipitation assay in detecting specific histone modifications in senescence-related genes including p53 and p16, it was demonstrated that the mRNA expression of p53 was associated with increased H4 acetylation in replicative senescence and increased H4 acetylation and trimethylation of histone H3 at lysine 4 (H3K4me3) in premature senescence. Both acetylation and trimethylation of H3 were involved in replicative senescence, while the acetylation of histone H3 and H4 was predominant in premature senescence, contributing to the mRNA expression of p16. In summary, the global hypoacetylation of histone H3 and H4 and the hypertrimethylation of histone H4 lysine 20 account for epigenetic characteristics in senescence, controlled by HATs, HMT, and HDACs differentially between replicative and premature senescence. Taken together, these findings suggest that the specific histone modifications are involved in regulating the expression of genes related to senescence of human embryonic lung fibroblasts.
组蛋白修饰是负责调节参与细胞衰老的基因转录的主要翻译后机制。通过免疫荧光和蛋白质印迹法，我们发现，在人胚肺成纤维细胞的复制性衰老和早衰过程中，组蛋白H3和H4的整体乙酰化水平均显著降低。然而，衰老细胞中组蛋白H4赖氨酸20的整体三甲基化水平更高。组蛋白乙酰转移酶（HATs）、组蛋白甲基转移酶（HMT）和组蛋白去乙酰化酶（HDACs）的mRNA和蛋白质水平的变化表明，复制性衰老细胞和早衰细胞之间存在差异表达。同时，HDACs活性的降低与细胞衰老相伴。通过采用定量染色质免疫沉淀试验检测衰老相关基因（包括p53和p16）中的特定组蛋白修饰，结果表明，p53的mRNA表达与复制性衰老中H4乙酰化增加以及早衰中H4乙酰化和组蛋白H3赖氨酸4三甲基化（H3K4me3）增加相关。H3的乙酰化和三甲基化均参与复制性衰老，而组蛋白H3和H4的乙酰化在早衰中占主导地位，促进p16的mRNA表达。总之，组蛋白H3和H4的整体低乙酰化以及组蛋白H4赖氨酸20的高甲基化构成了衰老过程中的表观遗传特征，在复制性衰老和早衰过程中分别由HATs、HMT和HDACs进行差异调控。综上所述，这些发现表明特定的组蛋白修饰参与调节人胚肺成纤维细胞衰老相关基因的表达。
