Author: Xueqing Lu
Publisher:
ISBN: 9780355754599
Category : Chromatin
Languages : en
Pages : 211
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Book Description
Approximately half of the world's population is at risk of malaria transmission, and this number can be expected to grow as drug resistant strains continue to develop. Among the human infectious Plasmodium species, Plasmodium falciparum causes the most severe and lethal form of malaria. This parasite has an extreme AT-rich genome and a complex life cycle that is likely to be regulated by coordinate changes in gene expression. However, the mechanisms behind this fine-tuned gene expression and regulation system remain elusive. For instance, only a limited number of transcription factors have been identified. Recent studies suggest that epigenetic and post-transcriptional regulation may be used as alternative regulation strategies to compensate for the lack of transcription factors in this parasite. Therefore, in this dissertation work, we further explored the transcriptome, epigenome, and the proteome to better understand the transcriptional mechanisms in P. falciparum. In chapter 1, we demonstrated that genes are usually defined by unique nucleosomal features and that nucleosome landscape alone could be used to identify novel genes in organisms with a nucleotide bias. Next, we investigated nascent RNA expression profiles and observed that the majority of genes are transcribed at the trophozoite stage in response to the open chromatin structure of that stage. These results helped us link chromatin reorganization events to transcriptional activity and highlighted the importance of epigenetic and post-transcriptional regulation in this parasite. Therefore, in the latter two chapters, we further examined the proteasome and transcriptome isolated from both nuclear and cytoplasmic fractions to identify potential chromatin regulators. As a result, we identified a large number of chromatin-associated proteins and lncRNAs that are likely to have important roles in chromatin regulation and post-transcriptional and translational regulations. Collectively, data and results from these studies will become stepping-stones for future malaria studies and further assist the identification of promising anti-malarial drug targets.
Author: Gayani Dinusha Batugedara
Publisher:
ISBN:
Category : Gene expression
Languages : en
Pages : 20
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Book Description
Collectively, our data highlight the importance of spatial genome organization as a mechanism of transcriptional regulation in malaria parasites, and our work directly addresses one of the central outstanding questions in Plasmodium biology, namely, how a parasite with approximately 6,000 genes manages to control gene expression in a coordinated fashion using a limited number of transcription factors.
Author: Anusha Madhuram Gopalakrishnan
Publisher:
ISBN:
Category :
Languages : en
Pages : 276
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Author: Koen Jakob Dechering
Publisher:
ISBN: 9789090119540
Category :
Languages : en
Pages : 139
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Author: Koen Dechering
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Author: Timothy Russell
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Plasmodium falciparum, the most virulent of the human infectious malaria parasites, caused over 600,000 deaths in 2020. Alarmingly, malaria deaths have increased since 2019 and resistance has been reported for every antimalarial drug deployed to date. Regulation of gene expression is critical for P. falciparum to complete its complex life cycle, which includes stages in the human host and Anopheles mosquito vector. Gene regulation in malaria parasites is primarily driven by the Apicomplexan AP2 (ApiAP2) proteins, a single expanded family of sequence specific DNA binding transcription factors. ApiAP2 proteins are plant derived and therefore have no homologs encoded in the human or mosquito genomes, making them potential drug targets. In order to exploit ApiAP2 proteins as antimalarial intervention targets, it is important to both identify ApiAP2 inhibitors and to probe the biological function of ApiAP2 proteins. In this thesis work, ApiAP2 proteins have been investigated to assess their biological functions and druggability. In Chapter 2, putative competitors of DNA binding by the ApiAP2 protein AP2-EXP were selected using an in silico screen. Several compounds were found to inhibit ApiAP2 DNA binding in vitro using DNA gel-shifts. An ApiAP2 competitor compound was then leveraged for use as a chemical genetic tool to interrogate the function of AP2-EXP. In Chapter 3, a potential cooperative interaction between the ApiAP2 proteins PfAP2-I and PfAP2-G during P. falciparum sexual development was interrogated by mapping the DNA binding occupancy of each protein. PfAP2-I genomic occupancy changes in the presence of PfAP2-G, indicating for the first time a causal relationship between two P. falciparum transcription factors that regulates DNA binding specificity. PfAP2-I and PfAP2-G co-occupancy coincides with the activation of P. falciparum sexual stage genes. In Chapter 4, the first indications of the gene regulatory functions of the ApiAP2 proteins PfAP2-HS and PfAP2-O3 were uncovered by mapping their genome-wide DNA binding occupancies. PfAP2-HS was found to regulate a transcription program that is required for P. falciparum to survive febrile host temperatures, while PfAP2-O3 primarily occupies the gene bodies of loci encoding tRNA and rRNA during sexual development. In aggregate, this thesis work describes efforts to further understand the unique ApiAP2 transcription factor proteins in the human malaria parasite P. falciparum.
Author: Victoria Bonnell
Publisher:
ISBN:
Category :
Languages : en
Pages : 0
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Book Description
Malaria, caused by protozoan parasites of the genus Plasmodium, remains a major global health burden, with 247 million cases and killing 619,000 in 2021 alone. In Plasmodium falciparum, the deadliest human malaria parasite, about 90% of the protein-coding genes are transcribed in a periodic fashion over the 48-hour intraerythrocytic development cycle (IDC), with the peak transcript abundance generally occurring just before the protein is required. The periodicity of transcription forms a genome-wide cascade of continuous gene expression, which is believed to be finely regulated by a limited number of transcriptional regulators, including the 30-member Apicomplexan APETALA2 (ApiAP2) family of sequence-specific transcription factors (TFs). Interestingly, this family of proteins has AP2 DNA-binding domains only evolutionarily conserved in plant-linage genomes and Apicomplexan parasites, making them potential drug targets for novel antimalarial therapeutics in humans. The current literature is focused only on identifying regulatory networks controlled by the ApiAP2 TFs; however, dissecting the molecular mechanisms of their genome-wide binding pattern is still understudied. Knowing mechanisms of binding site selection of putative drug targets is critical to identifying essential interactions or features to be blocked. This dissertation elucidates the biological function and binding specificity of a subset of ApiAP2 TFs, which each recognize similar DNA sequence motifs in vitro, along with their chromatin-remodeling interaction partners. This project applies in vitro, in vivo, and in silico approaches to identify how sequence preferences are established during parasite development by probing the effects of cis- and trans- regulation on TF binding, in addition to dissecting the function of these TFs in parasite development. In higher eukaryotes, TFs with similar binding preferences can carry out different regulatory functions in a given cell type, work synergistically or antagonistically, perform similar functions in different cell types, or can be fully redundant and only necessary in the event that the primary factor cannot function. The occurrence of multiple TFs recognizing similar DNA sequence motifs in P. falciparum is intriguing since functional gene redundancy is not often evolutionarily conserved in pathogens. Therefore, despite the similar DNA binding motifs of these proteins, we predict that they carry out distinct regulatory functions in the parasite. There are several established features investigated by this work that can modulate binding specificity of a TF such as: DNA sequence context/intrinsic DNA shape, interaction with cofactors, histone post-translational modification, and chromatin accessibility. It is critical to understand which features, or combinations thereof, influence binding specificity of transcriptional regulators in P. falciparum to inform future antimalarial drug development.
Author: Talat Afroze
Publisher:
ISBN:
Category :
Languages : en
Pages : 256
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Author: World Health Organization
Publisher: World Health Organization
ISBN: 9241565659
Category : Medical
Languages : en
Pages : 210
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Book Description
This year s report shows that after an unprecedented period of success in global malaria control progress has stalled. Data from 2015?2017 highlight that no significant progress in reducing global malaria cases was made in this period. There were an estimated 219 million cases and 435 000 related deaths in 2017. The World malaria report 2018 draws on data from 90 countries and areas with ongoing malaria transmission. The information is supplemented by data from national household surveys and databases held by other organizations.
Author: RieÌ8tte Andele̹ Van Biljon
Publisher:
ISBN:
Category : Malaria
Languages : en
Pages : 0
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The Plasmodium falciparum parasite, the major causative agent of malaria on the African continent, has evolved numerous cellular adaptations to effectively propagate its species. The parasite can proliferate asexually, producing mass amounts of progeny to subsist in the human host or differentiate into sexual forms (gametocytes) that, once mature, can transmit to a feeding Anopheles mosquito. Key to our ability to effectively develop chemical candidates that interfere with either of these processes is the identification and understanding of critical factors that regulate parasite development. This is particularly true for the development of antimalarials that can be used in malaria elimination strategies by targeting both parasite proliferation and transmission. We therefore hypothesized that parasite proliferation and differentiation use divergent mechanisms for gene expression that could be observed through a thorough investigation of the functional genome of these different parasite forms. This doctoral study therefore set out to increase our knowledge base on three crucial aspects of parasite development: 1) the atypical cell cycle that allows the rapid proliferation of asexual parasites; 2) the full molecular profile of gametocytogenesis enabling the cellular differentiation that allows the parasite to transmit; and 3) the metabolic differences between these proliferating and differentiating parasites that results from their strategy-specific mechanisms of developmental control. The atypical cell cycle of the parasite, associated with the massive cell number expansion in asexual development, is notoriously difficult to study. Here, we contributed a novel system by developing a cell cycle synchronization tool that reversibly blocks the development of asexual parasites at the G1/S transition. This results in an inescapable arrest of the cell cycle that is completely and functionally reversible; parasites re-initiate cell cycle progression and continue to S phase within 6 h. This system provided the opportunity to characterize cell cycle phases in the parasite and additionally evaluate molecular mechanisms associated with cell cycle arrest or re-initiation. During cell cycle arrest, the parasite enters a quiescent state reminiscent of a mitogen-activated restriction point. This arrest is unique and solely attributed to the removal of the specific mitogens within this system, polyamines. These analyses indicate the close interaction between transcriptional regulation and signal transduction cascades in the progression through the parasite℗þs cell cycle and for the first time highlight aspects of controlled cell cycle regulation in Plasmodium. In contrast to proliferation, the process of sexual differentiation only started receiving attention in the past few years. As such, we lack fundamental understanding of the mechanisms driving the unique gametocyte differentiation of P. falciparum parasites. This study contributes a detailed analysis of gametocyte differentiation that revealed distinct developmental transitions demarcating the start of gametocytogenesis, intermediate gametocyte development and finally maturation to produce the transmissible mature gametocytes. The study provides evidence for coordinated regulation of gene expression on a transcriptional level. We propose a model for regulation of gametocytogenesis in malaria parasites that involves active repression of gene sets mediated through epigenetics and RNA destabilization as well as active transcription of gene sets through successive ApiAP2 transcription factor activity. This data provides the most detailed framework of coordinated gene regulation events underlying development of P. falciparum gametocytes to date, a unique resource for the malaria community. The comprehensive and complex transcriptional regulation described for the proliferation and differentiation of the parasite led us to evaluate the functional consequence thereof. A whole cell phenotype microarray system was evaluated for its ability to measure the metabolic processes that define asexual and sexual stage metabolism as a functional consequence of changed gene expression profiles during proliferation and differentiation. The study provided metabolic profiles detailing carbon and nitrogen metabolism in asexual parasites, mature and immature gametocyte stages. The data highlighted dipeptide metabolism as a distinguishing feature in mature gametocytes and showed the presence of a low, delayed metabolic state concurrent with reduced transcriptional activity observed in this stage. These results show that gene expression changes associated with differentiation compared to proliferation translate to an observable metabolic phenotype and that transcriptional regulation shapes the molecular landscape underlying crucial events that enable the parasite℗þs intraerythrocytic asexual and sexual development.
