G-quadruplex biology in the human malaria parasite Plasmodium falciparum

人类疟原虫恶性疟原虫中的 G-四联体生物学

• 批准号: MR/P010873/1
• 负责人: Catherine Merrick
• 金额: $ 62.31万
• 依托单位: Keele University
• 依托单位国家: 英国
• 项目类别: Research Grant
• 财政年份: 2017
• 资助国家: 英国
• 起止时间: 2017 至 无数据
• 项目状态: 已结题
• 来源: https://gtr.ukri.org/projects?ref=MR%2FP010873%2F1
• 关键词: quadruplex; biology; human; malaria; parasite

The proposed research concerns the most important human malaria parasite, Plasmodium falciparum. Malaria is one of the world's most debilitating infectious diseases, killing over half a million people every year and affecting several hundred million. Most of the deaths occur in young children in sub-Saharan Africa, but adults can also suffer from malaria throughout their lives, reducing quality of life and retarding economic development in endemic countries. The lack of an effective vaccine and the emergence of drug-resistant parasites mean that there is now an urgent need for research leading to a better understanding of the malaria parasite, and hence to new vaccine targets and treatment strategies for this disease.The malaria parasite causes illness via the infection of red blood cells. It multiplies inside these cells and modifies their surfaces with proteins called PfEMP1s that bind to the walls of blood vessels. This is crucial for parasite survival as it removes infected cells from the circulating blood and protects them from passing through the spleen, which might recognize and destroy them. It also contributes to disease, with severe malaria being particularly associated with the accumulation of infected cells in vessels of the brain and placenta. It is therefore of great interest to malaria biologists to understand the mechanisms that control the expression of these adhesive PfEMP1 proteins. PfEMP1s are not expressed uniformly by all malaria parasites: instead, individual parasites regularly switch between different variants. This allows them to stay ahead of the immune system and sustain a chronic infection for months or even years. The parasites have a large, variable family of 'var' genes for different PfEMP1 proteins and they vary the expression of these genes by so-called 'epigenetic switching'. Furthermore, var genes recombine very readily to generate new variants, so each parasite strain - of which there are many hundreds circulating in endemic areas - has a unique repertoire of possible surface proteins. This is one reason why immunity to repeated malaria infections is slow to develop in humans: every new parasite strain looks different to the immune system, so people can be re-infected repeatedly throughout their lives.Understanding and ultimately interfering with the expression, switching and recombination of var genes, and thus the variant expression of PfEMP1 proteins, could be a key to more effective immune control of malaria. Therefore, this research focuses on a new biological mechanism that the parasite may use for switching between var genes and for generating new variants. Our recent work has showed that an unusual DNA structure called a G-quadruplex that is concentrated around var genes seems to affect both these processes. To investigate this further, we now propose to map the G-quadruplexes throughout the Plasmodium genome, both in DNA and also in the messenger molecule, RNA. We will use a range of cutting-edge genome-wide technologies to do this, and will then check whether the distribution of the structures changes when the enzymes that unwind them are removed.These studies will lead to a better understanding of the mechanisms underlying var gene dynamics, and may ultimately inform new strategies to combat malaria, since var genes - and the adhesive proteins that they encode - are central to malarial disease. The outcomes of the research will be published in open-access scientific journals and presented at international conferences. They will be communicated to the general public via summaries on appropriate websites and via science writing in magazines and/or online. Work such as this remains vital as long as the malaria parasite continues to cause an immense burden of human disease.

这项拟议中的研究涉及最重要的人类疟疾寄生虫--恶性疟原虫。疟疾是世界上最严重的传染病之一，每年造成50多万人死亡，数亿人受到影响。大多数死亡发生在撒哈拉以南非洲的幼儿中，但成年人也可能终生遭受疟疾之害，降低了疟疾流行国家的生活质量，阻碍了经济发展。缺乏有效的疫苗和抗药性寄生虫的出现意味着现在迫切需要进行研究，以更好地了解疟疾寄生虫，从而为这种疾病找到新的疫苗靶点和治疗策略。疟疾寄生虫通过感染红细胞引起疾病。它在这些细胞内繁殖，并用称为PfEMP 1的蛋白质修饰它们的表面，这些蛋白质与血管壁结合。这对寄生虫的生存至关重要，因为它从循环血液中清除感染的细胞，并保护它们不通过脾脏，脾脏可能会识别并摧毁它们。它也会导致疾病，严重的疟疾特别与大脑和胎盘血管中受感染细胞的积累有关。因此，疟疾生物学家对了解控制这些粘附性PfEMP 1蛋白表达的机制非常感兴趣。PfEMP 1并不是所有疟原虫都能一致表达的：相反，单个疟原虫会定期在不同的变体之间切换。这使它们能够领先于免疫系统，并持续数月甚至数年的慢性感染。寄生虫有一个大的，可变的家庭的'var'基因的不同PfEMP 1蛋白，他们改变这些基因的表达，所谓的'表观遗传开关'。此外，var基因很容易重组产生新的变体，因此每一种寄生虫菌株--在流行地区有数百种--都有一套独特的可能的表面蛋白。这就是为什么人类对反复感染疟疾的免疫力发展缓慢的原因之一：每一种新的寄生虫株在免疫系统中看起来都不一样，所以人们一生中可能会反复感染。了解并最终干预var基因的表达、转换和重组，以及PfEMP 1蛋白的变异表达，可能是更有效地免疫控制疟疾的关键。因此，这项研究的重点是一种新的生物学机制，寄生虫可能用于在var基因之间切换并产生新的变体。我们最近的工作表明，一种不寻常的DNA结构，称为G-四链体，集中在var基因周围，似乎影响了这两个过程。为了进一步研究这一点，我们现在建议在整个疟原虫基因组中绘制G-四链体，包括DNA和信使分子RNA。我们将使用一系列尖端的全基因组技术来做这件事，然后将检查当解开它们的酶被移除时，结构的分布是否会发生变化。这些研究将有助于更好地理解var基因动力学背后的机制，并可能最终为对抗疟疾的新策略提供信息，因为变异基因--以及它们编码的粘附蛋白--是疟疾的核心。研究成果将发表在开放获取的科学期刊上，并在国际会议上发表。将通过适当网站上的摘要以及杂志和/或在线上的科学文章向公众传达。只要疟疾寄生虫继续给人类造成巨大的疾病负担，这类工作就仍然至关重要。

项目成果

RecQ helicases and quadruplex structures in var gene evolution and expression

var 基因进化和表达中的 RecQ 解旋酶和四链体结构

• 发表时间: 2018
• 作者: Merrick, C J

RecQ helicases in the malaria parasite Plasmodium falciparum affect genome stability, gene expression patterns and DNA replication dynamics.

• DOI: 10.1371/journal.pgen.1007490
• 发表时间: 2018-07
• 期刊: PLoS genetics
• 影响因子: 4.5
• 作者: Claessens A;Harris LM;Stanojcic S;Chappell L;Stanton A;Kuk N;Veneziano-Broccia P;Sterkers Y;Rayner JC;Merrick CJ
• 通讯作者: Merrick CJ

G-quadruplex RNA motifs influence gene expression in the malaria parasite Plasmodium falciparum.

• DOI: 10.1093/nar/gkab1095
• 发表时间: 2021-12-02
• 期刊: Nucleic acids research
• 影响因子: 14.9
• 作者: Dumetz F;Chow EY;Harris LM;Liew SW;Jensen A;Umar MI;Chung B;Chan TF;Merrick CJ;Kwok CK
• 通讯作者: Kwok CK

A novel putative telomere-binding protein in Plasmodium falciparum (poster presentation, MPM 2019)

恶性疟原虫中一种新的假定端粒结合蛋白（海报展示，MPM 2019）

• 发表时间: 2019
• 作者: Edwards-Smallbone, J

The in vivo RNA structurome of the malaria parasite Plasmodium falciparum , a protozoan with an A/T-rich transcriptome

疟原虫恶性疟原虫（一种富含 A/T 转录组的原生动物）的体内 RNA 结构组

• DOI: 10.1101/2021.04.29.441925
• 发表时间: 2021
• 作者: Dumetz F