Diarrheal disease caused by Giardia duodenalis is highly prevalent, causing over 200 million cases globally each year. The processes that drive parasite virulence, host immune evasion and transmission involve coordinated gene expression and have been linked to epigenetic regulation. Epigenetic regulatory systems are eukaryote-conserved, including in deep branching excavates such as Giardia, with several studies already implicating histone post-translational modifications in regulation of its pathogenesis and life cycle. However, further insights into Giardia chromatin dynamics have been hindered by a lack of site-specific knowledge of histone modifications. Using mass spectrometry, we have provided the first known molecular map of histone methylation, acetylation and phosphorylation modifications in Giardia core histones. We have identified over 50 previously unreported histone modifications including sites with established roles in epigenetic regulation, and co-occurring modifications indicative of post-translational modification crosstalk. These demonstrate conserved histone modifications in Giardia which are equivalent to many other eukaryotes, and suggest that similar epigenetic mechanisms are in place in this parasite. Further, we used sequence, domain and structural homology to annotate putative histone enzyme networks in Giardia, highlighting representative chromatin modifiers which appear sufficient for identified sites, particularly those from H3 and H4 variants. This study is to our knowledge the first and most comprehensive, complete and accurate view of Giardia histone post-translational modifications to date, and a substantial step towards understanding their associations in parasite development and virulence.

由十二指肠贾第鞭毛虫引起的腹泻病非常普遍，每年在全球造成超过 2 亿例病例。驱动寄生虫毒力、宿主免疫逃避和传播的过程涉及协调的基因表达，并与表观遗传调控有关。表观遗传调控系统是真核生物保守的，包括在诸如贾第鞭毛虫的深层分支挖掘物中，一些研究已经表明组蛋白翻译后修饰对其发病机制和生命周期的调控。然而，进一步了解贾第虫由于缺乏组蛋白修饰的特定位点知识，染色质动力学受到阻碍。使用质谱法，我们提供了贾第鞭毛虫核心组蛋白中组蛋白甲基化、乙酰化和磷酸化修饰的第一个已知分子图。我们已经确定了 50 多种以前未报告的组蛋白修饰，包括在表观遗传调控中具有既定作用的位点，以及表明翻译后修饰串扰的共同发生的修饰。这些证明贾第鞭毛虫中保守的组蛋白修饰与许多其他真核生物等效，并表明这种寄生虫存在类似的表观遗传机制。此外，我们使用序列、域和结构同源性来注释推定的组蛋白酶网络贾第鞭毛虫，突出显示足以识别位点的代表性染色质修饰符，尤其是来自 H3 和 H4 变体的那些。据我们所知，这项研究是迄今为止对贾第鞭毛虫组蛋白翻译后修饰的第一个也是最全面、最完整和最准确的观点，也是了解它们在寄生虫发育和毒力中的关联的重要一步。