组蛋白H3K14M突变对嗜肺军团菌来源甲基转移酶活性的抑制

Inhibition of the activity of methyltransferase from Legionella pneumophila by histone H3K14M mutation

目的·探讨真核细胞中组蛋白H3K14M突变对嗜肺军团菌分泌的甲基转移酶RomA活性的影响及其内在机制。方法·构建组蛋白H3野生型(H3WT)以及组蛋白H3上14位赖氨酸突变为甲硫氨酸、异亮氨酸、精氨酸(H3K14M、H3K14I、H3K14R)的真核表达质粒,慢病毒包装并感染稳定表达RomA的293T、THP-1等细胞。用Western blotting检测并比较带有不同H3K14突变的细胞中内源H3K14位点表观修饰的改变。并利用免疫共沉淀技术检测H3K14M与RomA蛋白的相互作用。结果·嗜肺军团菌的分泌效应物RomA通过靶向宿主细胞核,增加其H3K14甲基化水平同时降低H3K14乙酰化水平,从而抑制宿主基因的表达,促进嗜肺军团菌有效的细胞内复制;但组蛋白H3K14M突变可以通过增强与RomA蛋白的相互作用以抑制其甲基转移酶活性,阻断RomA对H3K14位点的甲基化。结论·组蛋白H3K14M突变显著抑制嗜肺军团菌来源甲基转移酶RomA活性。

Objective · To investigate the effect of histone H3K14M mutation on the activity of methyltransferase RomA, a secreted effector of Legionella pneumophila in eukaryotic cells and the underlying mechanisms. Methods · Wide-type histone H3 (H3WT) and mutant histone H3 (the lysine residue 14 was replaced by methionine, isoleucine or arginine residue, and named as H3K14M, H3K14I, and H3K14R, respectively) recombinant expression plasmids were constructed. Packaged lentiviruses with these plasmids were used to infect eukaryotic cells 293T and THP-1 with or without over-expression of RomA. The H3K14 methylation and acetylation were analyzed by Western blotting. The interaction of RomA with H3WT and H3K14 mutants was detected by co-immunoprecipitation. Results · A secreted effector of Legionella pneumophila named RomA targeted the host cell nucleus to upregulate the H3K14 methylation level and downregulate the H3K14 acetylation level for inhibiting the gene expression in host cells and promoting Legionella pneumophila's efficient intracellular replication. But histone H3K14M mutation could promote the interaction between H3K14M and RomA and thus inhibited the methyltransferase activity of RomA. Conclusion · Histone H3K14M mutation significantly inhibits the activity of Legionella pneumophila methyltransferase RomA.