Department of Biology, Harvey Mudd College, Claremont, California, USA.
Department of Mathematics and Statistics, Pomona College, Claremont, California, USA.
Microbiol Spectr. 2023 Jun 15;11(3):e0014723. doi: 10.1128/spectrum.00147-23. Epub 2023 Apr 25.
The eukaryotic protozoan parasite Trypanosoma brucei is transmitted by the tsetse fly to both humans and animals, where it causes a fatal disease called African trypanosomiasis. While the parasite lacks canonical DNA sequence-specific transcription factors, it does possess histones, histone modifications, and proteins that write, erase, and read histone marks. Chemical inhibition of chromatin-interacting bromodomain proteins has previously been shown to perturb bloodstream specific trypanosome processes, including silencing of the variant surface glycoprotein (VSG) genes and immune evasion. Transcriptomic changes that occur in bromodomain-inhibited bloodstream parasites mirror many of the changes that occur as parasites developmentally progress from the bloodstream to the insect stage. We performed transcriptome sequencing (RNA-seq) time courses to determine the effects of chemical bromodomain inhibition in insect-stage parasites using the compound I-BET151. We found that treatment with I-BET151 causes large changes in the transcriptome of insect-stage parasites and also perturbs silencing of VSG genes. The transcriptomes of bromodomain-inhibited parasites share some features with early metacyclic-stage parasites in the fly salivary gland, implicating bromodomain proteins as important for regulating transcript levels for developmentally relevant genes. However, the downregulation of surface procyclin protein that typically accompanies developmental progression is absent in bromodomain-inhibited insect-stage parasites. We conclude that chemical modulation of bromodomain proteins causes widespread transcriptomic changes in multiple trypanosome life cycle stages. Understanding the gene-regulatory processes that facilitate transcriptome remodeling in this highly diverged eukaryote may shed light on how these mechanisms evolved. The disease African trypanosomiasis imposes a severe human and economic burden for communities in sub-Saharan Africa. The parasite that causes the disease is transmitted to the bloodstream of a human or ungulate via the tsetse fly. Because the environments of the fly and the bloodstream differ, the parasite modulates the expression of its genes to accommodate two different lifestyles in these disparate niches. Perturbation of bromodomain proteins that interact with histone proteins around which DNA is wrapped (chromatin) causes profound changes in gene expression in bloodstream-stage parasites. This paper reports that gene expression is also affected by chemical bromodomain inhibition in insect-stage parasites but that the genes affected differ depending on life cycle stage. Because trypanosomes diverged early from model eukaryotes, an understanding of how trypanosomes regulate gene expression may lend insight into how gene-regulatory mechanisms evolved. This could also be leveraged to generate new therapeutic strategies.
真核原生动物寄生虫布氏锥虫通过采采蝇传播给人类和动物,在那里它会引起一种致命的疾病,称为非洲锥虫病。虽然寄生虫缺乏典型的 DNA 序列特异性转录因子,但它确实拥有组蛋白、组蛋白修饰以及书写、擦除和读取组蛋白标记的蛋白质。先前的研究表明,化学抑制染色质相互作用的溴结构域蛋白会扰乱血液阶段寄生虫的特定过程,包括变体表面糖蛋白 (VSG) 基因的沉默和免疫逃避。在溴结构域抑制的血液寄生虫中发生的转录组变化反映了寄生虫从血液阶段到昆虫阶段发育过程中发生的许多变化。我们进行了转录组测序 (RNA-seq) 时间过程,以使用化合物 I-BET151 确定化学溴结构域抑制对昆虫阶段寄生虫的影响。我们发现,用 I-BET151 处理会导致昆虫阶段寄生虫的转录组发生巨大变化,并扰乱 VSG 基因的沉默。溴结构域抑制的寄生虫的转录组与蝇唾液腺中的早期循环阶段寄生虫具有一些共同特征,这表明溴结构域蛋白对于调节与发育相关基因的转录水平很重要。然而,在溴结构域抑制的昆虫阶段寄生虫中,通常伴随发育进展的表面原头蚴蛋白的下调不存在。我们得出的结论是,化学调节溴结构域蛋白会导致多个锥虫生命周期阶段的广泛转录组变化。了解促进这种高度分化的真核生物转录组重塑的基因调控过程可能揭示这些机制的进化方式。这种疾病非洲锥虫病给撒哈拉以南非洲社区的人类和经济带来了严重的负担。引起这种疾病的寄生虫通过采采蝇传播到人类或有蹄类动物的血液中。由于蝇和血液的环境不同,寄生虫会调节其基因的表达,以适应这两个不同生境中的两种不同生活方式。干扰与围绕 DNA 缠绕的组蛋白相互作用的溴结构域蛋白会导致血液阶段寄生虫的基因表达发生深刻变化。本文报道称,化学溴结构域抑制也会影响昆虫阶段寄生虫的基因表达,但受影响的基因因生命周期阶段而异。由于锥虫与模型真核生物早期分化,了解锥虫如何调节基因表达可能有助于了解基因调控机制的进化方式。这也可以被利用来产生新的治疗策略。
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