Project description:Background Histone deacetylase (HDACs) inhibitors are being intensively pursued as potential new antimalarial drugs, and are also emerging as valuable tools for investigating transcriptional control in malaria parasites. In this study, the genome-wide transcriptional effects of three structurally related hydroxamate HDAC inhibitors were profiled in Plasmodium falciparum, the most lethal of the malaria parasite species that infects humans. Results Following 2h exposure to trichostatin A (TSA), suberoylanilide hydroxamic acid (SAHA) or a 2-aminosuberic acid derivative (2-ASA-9), ~18-28% of genes in P. falciparum trophozoite-stage parasites were regulated greater than two fold. This global induction was transitory, with fewer genes (3-5%) regulated after removing the compounds and culturing for a further 2h. Just nine genes, including alpha-II-tubulin, were up-regulated by all three compounds. Despite structural similarity, the three inhibitors caused quite diverse transcriptional effects, possibly reflecting subtle differences in mode of action or cellular distribution. Conclusions Three structurally related HDAC inhibitors have been found to cause profound, genome-wide, transcriptional changes in P. falciparum parasites, but most effects were transitory. This highlights the dynamic and exquisitely controlled nature of transcription in these malaria parasites. We also identified a small subset of nine genes over-expressed by all three HDAC inhibitors that may represent the first recognized set of transcriptional markers that signify HDAC inhibition in malaria parasites. This data set is an important contribution to our understanding of gene regulation in malaria parasites and supports growing evidence for the potential of HDAC inhibitors as new antimalarial agents.
Project description:Little is known about the role of the three Jumonji C (JmjC) enzymes in Plasmodium falciparum (Pf). Here, we show that JIB-04 and other established inhibitors of mammalian JmjC histone demethylases kill asexual blood stage parasites and are even more potent at blocking gametocyte development and gamete formation. In late stage parasites, JIB-04 increased levels of trimethylated lysine residues on histones, suggesting the inhibition of P. falciparum Jumonji demethylase activity. These epigenetic defects coincide with deregulation of invasion, cell motor, and sexual development gene programs, including gene targets coregulated by the PfAP2-I transcription factor and chromatin-binding factor, PfBDP1. Mechanistically, we demonstrate that PfJmj3 converts 2-oxoglutarate to succinate in an iron-dependent manner consistent with mammalian Jumonji enzymes, and this catalytic activity is inhibited by JIB-04 and other Jumonji inhibitors. Our pharmacological studies of Jumonji activity in the malaria parasite provide evidence that inhibition of these enzymatic activities is detrimental to the parasite.
Project description:In the malaria parasite Plasmodium falciparum, the expression of many genes is regulated by heterochromatin (HC) based on the histone mark tri-methylation of histone H3 lysine 9 (H3K9me3). HC assembly involves three distinct steps: de novo nucleation, spreading and maintenance. Nucleation, which consists in formation of HC in a previously euchromatic region, determines at which specific regions of the genome HC occurs, but this process is not well understood in malaria parasites. Here we investigated the DNA sequence cis determinants of HC nucleation in P. falciparum, using a screening approach based on integration of fragments from different heterochromatic genes into an euchromatic locus, followed by chromatin immunoprecipitation (ChIP). We found that fragments of var gene upstream regions nucleated HC efficiently, whereas fragments from the pfap2-g upstream region or from the mspdbl2 locus did not nucleate HC. Fragments from the beginning of the coding sequence (CDS) of pfap2-g nucleated HC with low efficiency, as evidenced by nucleation requiring long fragments of ~2 kb and occurring only in a fraction of the parasites. These results demonstrate that the primary DNA sequence is a main determinant of HC nucleation in P. falciparum. We also studied HC maintenance at the pfap2-g locus, which demonstrated that specific parts of the upstream region, different from the regions competent for HC nucleation, are required for maintenance. Together, our results provide initial insight into how HC is directed to specific loci and maintained in P. falciparum.
Project description:Transcriptional profiling of P. falciparum comparing parasites exposed to 5% and 21% oxygen environmental conditions in the late ring stage.
Project description:The dry season is a major challenge for Plasmodium falciparum parasites in many malaria endemic regions, where water availability limits mosquitoes to only part of the year. How P. falciparum bridges two transmission seasons months apart, without being cleared by the host or compromising host survival is poorly understood. Here we show that low levels of P. falciparum parasites persist in the blood of asymptomatic Malian individuals during the 5- to 6-month dry season, rarely causing symptoms and minimally affecting the host immune response. Parasites isolated during the dry season are transcriptionally distinct from those of subjects with febrile malaria in the transmission season, reflecting longer circulation within each replicative cycle, of parasitized erythrocytes without adhering to the vascular endothelium. Low parasite levels during the dry season are not due to impaired replication, but rather increased efficiency of splenic clearance of longer-circulating infected erythrocytes. We propose that P. falciparum virulence in areas of seasonal malaria transmission is regulated so that the parasite decreases its endothelial binding capacity, allowing increased splenic clearance and enabling several months of subclinical parasite persistence.
Project description:The MORC (microrchidia) family of proteins is highly conserved in all eukaryotic cells and have been shown to play diverse roles by forming protein-protein interactions with immune-responsive proteins, SWI chromatin remodeling complexes, histone deacetylases, and histone tail modifications across metazoans. To dissect the functional roles of MORC in the human malaria parasite, Plasmodium falciparum, we developed a glmS based ribozyme knockdown system to induce PfMORC knockdown upon glucosamine (GlcN) induction. We further conducted a transcriptomic analysis in PfMORC-HA-glmS knockdown parasites at the asexual stage to investigate alterations in global gene expression. Our results indicate an overrepresentation of downregulated genes belonging to the heterochromatin-associated hypervariable gene family proteins. Overall, we found that PfMORC controls the asexual gene expression of the P. falciparum and can be a potential target for malaria disease containment.
Project description:In malaria infection, Plasmodium spp. parasites accumulate in the bone marrow near sites of erythroid development. While it has been observed that Plasmodium falciparum infection of late-stage erythroblasts can delay terminal erythroid differentiation and enucleation, the mechanism(s) underlying this phenomenon are unknown. Here, we apply RNA-seq after fluorescence-activated cell sorting (FACS) of infected erythroblasts to identify transcriptional responses to direct and indirect interaction with P. falciparum.
Project description:The study aims to investigate functions of two PfNOT1 paralogues in regulating gene expression in the malaria parasite, P. falciparum. To achieve this goal, the transcriptional profilling of parasites lacking PfNot1.1 or PfNOT1.2 was analyzed by microarray technology.
Project description:Here, we characterize the Plasmodium falciparum NEDD8 and demonstrate that P. falciparum cullins are NEDD8 substrates. This work lays the foundation for understanding the role of protein neddylation in malaria parasites.