摘要
文章以原代海马神经元为模型,探讨慢性铅暴露对组蛋白H3K4甲基化转移酶Kmt2a(MLL1)的影响及潜在机制。将原代海马神经元细胞分为空白对照组和慢性铅暴露实验组。实验组在第3天加入5μmol/L的醋酸铅暴露至第14天。通过Western blot检测MLL1以及组蛋白H3K4的甲基化蛋白表达量,定量聚合酶链式反应(quantitative polymerase chain reiciton,Q-PCR)检测甲基化转移酶、去甲基化转移酶以及相关LncRNA的mRNA表达量。结果显示:铅暴露显著降低了MLL1蛋白的相对质量,且其mRNA的水平也显著降低,但是作为MLL1的下游H3K4me2和H3K4me3的蛋白相对质量并没有产生显著性变化。Q-PCR结果显示,与对照组相比,另一种亚型组蛋白H3K4甲基化转移酶Kmt2b的mRNA水平不变,同时H3K4去甲基化酶Kdm1a的mRNA表达量显著降低,而Kdm5a不变。另外,H3K4me3的下游基因Nrg1和Meis2的mRNA水平均显著降低,并且具有招募功能的4种LncRNA(Evx1as、Hoxb5/6as、Malat1、MIAT)的mRNA水平均显著上升。该研究结果表明,慢性铅暴露环境对于H3K4甲基化的蛋白总量并没有产生影响,但是影响了其在染色质中的分布,并且这一过程可能是受上游LncRNA的调控实现的。
The effect of chronic lead exposure on histone H3K4 methyltransferase Kmt2a(MLL1)and its underlying mechanism in primary hippocampal neurons were investigated.Primary hippocampal neurons were divided into blank control group and chronic lead exposure group.In the experimental group,5μmol/L lead acetate was added on the third day to the 14 th day.MLL1 and histone H3K4 methylation expression was detected by Western blot.Quantitative polymerase chain reaction(QPCR)assay was applied to measuring methyltransferase,demethyltransferase and related LncRNA expression.The results indicated that lead exposure significantly reduced MLL1 protein expression and mRNA expression.But the downstream H3K4 me2 and H3K4 me3 of MLL1 had not changed.QPCR results showed that the mRNA level of histone H3K4 methyltransferase Kmt2 bwas unchanged compared with the control group.But the expression of H3K4 demethylase Kdm1 asignificantly decreased and Kdm5 awas unchanged.And the mRNA levels of Nrg1 and Meis2 significantly decreased.The mRNA levels of four LncRNAs(Evx1 as,Hoxb5/6 as,Malat1,MIAT)with recruitment functionincreased significantly.This study concluded that chronic lead exposure had no effect on the total amount of H3K4 methylated protein,but it affected its distribution in chromatin and this process might be regulated by the upstream LncRNA.
引文
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