Max Planck Institute for Infection Biology, Department of Molecular Biology, Berlin, Germany.
Epigenetics. 2009 Nov 16;4(8):577-86. doi: 10.4161/epi.4.8.10217.
Post-translational modifications of core histones are important components of the epigenetic landscape. Recent investigations of bacterial or toxin-induced effects on histone phosphorylation and acetylation in host cells have linked the changes to transcriptional alterations of key cellular response pathways. However, these changes may have other reasons and functional consequences. Here, we show that infection of gastric epithelial cell lines with the carcinogenic bacterium Helicobacter pylori leads to changes in histone H3 phosphorylation: type IV secretion system (T4SS)-dependent decreases of H3 phosphorylation levels at serine 10 (pH3Ser10) and threonine 3 (pH3Thr3) were observed. Immunofluorescence experiments with pH3Ser10 and cyclin B1 revealed that a H. pylori-induced transient pre-mitotic arrest was responsible for the observed reduction. This causal link was substantiated further by showing that H. pylori causes a strong decrease of the cell division cycle 25 (CDC25C) phosphatase. As a consequence, mitotic histone H3 kinases such as vaccinia-related kinase 1 (VRK1) and Aurora B were not fully activated in infected cells. We show that VRK1 activity, measured using a kinase activity assay, was reduced after H. pylori infection by approximately 40%. Moreover, overexpression of VRK1, but not Aurora B, compensated for the H. pylori-induced decrease of pH3Ser10. Rephosphorylation of H3Ser10 was IkappaB kinase alpha (IKKalpha)-dependent and occurred at later time points of infection. Taken together, our work highlights the impact of bacterial pathogens on host cell chromatin; this modulation reflects the subversion of key cellular processes such as cell cycle progression.
核心组蛋白的翻译后修饰是表观遗传景观的重要组成部分。最近的研究表明，细菌或毒素诱导的宿主细胞组蛋白磷酸化和乙酰化的变化与关键细胞反应途径的转录改变有关。然而，这些变化可能有其他原因和功能后果。在这里，我们表明，致癌细菌幽门螺杆菌感染胃上皮细胞系会导致组蛋白 H3 磷酸化发生变化：观察到 IV 型分泌系统（T4SS）依赖性的丝氨酸 10（pH3Ser10）和苏氨酸 3（pH3Thr3）处 H3 磷酸化水平降低。用 pH3Ser10 和细胞周期蛋白 B1 进行免疫荧光实验表明，幽门螺杆菌诱导的短暂有丝分裂前停滞是导致观察到的减少的原因。通过进一步表明幽门螺杆菌会强烈降低细胞分裂周期 25（CDC25C）磷酸酶，进一步证实了这种因果关系。因此，有丝分裂组蛋白 H3 激酶，如痘苗相关激酶 1（VRK1）和 Aurora B，在感染细胞中未被完全激活。我们表明，用激酶活性测定法测量的 VRK1 活性在幽门螺杆菌感染后降低了约 40%。此外，VRK1 的过表达，而不是 Aurora B 的过表达，补偿了幽门螺杆菌诱导的 pH3Ser10 减少。H3Ser10 的重新磷酸化依赖于 IkappaB 激酶 alpha（IKKalpha），并发生在感染的后期时间点。总之，我们的工作强调了细菌病原体对宿主细胞染色质的影响；这种调节反映了关键细胞过程的颠覆，如细胞周期进程。
