Biology subjects

Ngwa, C. J.

Publications and source records attributed to Ngwa, C. J..

3 recordsLinked to original sources

bioRxiv2024

Plasmodium falciparum SET10 is a histone H3 lysine K18 methyltransferase that participates in a chromatin modulation network crucial for intraerythrocytic development

Lifecycle progression of the malaria parasite Plasmodium falciparum requires precise tuning of gene expression including histone methylation. The histone methyltransferase PfSET10 was previously described as a H3K4 methyltransferase involved in var gene regulation, making it a prominent antimalarial target. In this study, we investigate the role of PfSET10 in the blood stages of P. falciparum in more detail, using tagged PfSET10-knockout (KO) and -knockdown (KD) lines. We demonstrate a nuclear localization of PfSET10 with peak protein levels in schizonts. PfSET10 deficiency results in reduced intraerythrocytic growth, but has no effect on gametocyte formation. When the PfSET10-KO line is screened for histone methylation variations, lack of PfSET10 renders the parasites unable to mark H3K18me1, while no significant changes in the H3K4 methylation status are observed. Comparative transcriptomic profiling of PfSET10-KO schizonts demonstrates the upregulation of transcripts particularly encoding proteins linked to erythrocyte invasion and multigene family proteins, suggesting a repressive function of the histone methylation mark. TurboID coupled with mass spectrometry further reveals an extensive nuclear PfSET10 interaction network with roles in transcriptional regulation, DNA replication and repair, chromatin remodeling and mRNA processing. Main interactors of PfSET10 include ApiAP2 transcription factors, chromatin modulators like PfMORC and PfISWI, mediators of RNA polymerase II, and DNA replication licensing factors. The combined data pinpoint PfSET10 as a histone H3 lysine K18 methyltransferase of the P. falciparum blood stages that regulates nucleic acid metabolic processes as part of a comprehensive chromatin modulation network. ImportanceThe fine-tuned regulation of DNA replication and transcription is particularly crucial for the rapidly multiplying blood stages of malaria parasites and proteins involved in these processes represent important drug targets. This study demonstrates that contrary to previous reports the histone methyltransferase PfSET10 of the malaria parasite Plasmodium falciparum methylates histone 3 at lysine K18, a histone mark to date not well understood. Deficiency of PfSET10 due to genetic knockout affects genes involved in intraerythrocytic development. Furthermore, in the nuclei of blood stage parasites, PfSET10 interacts with various protein complexes crucial for DNA replication, remodeling and repair, as well as for transcriptional regulation and mRNA processing. In summary, this study highlights PfSET10 as a H3K18 methyltransferase with critical functions in chromatin maintenance during the development of P. falciparum in red blood cells.

microbiology↗

bioRxiv2023

The Plasmodium falciparum CCCH zinc finger protein MD3 regulates male gametocytogenesis through its interaction with RNA-binding proteins

Malaria transmission to mosquitoes is dependent on the formation of gametocytes. When fully matured, gametocytes are able to transform into gametes in the mosquitos midgut, a process accompanied with their egress from the enveloping erythrocyte. Gametocyte maturation and gametogenesis require a well-coordinated gene expression programme that involves a wide spectrum of regulatory proteins, ranging from histone modifiers to transcription factors to RNA-binding proteins. Here, we investigated the role of the CCCH-zinc finger protein MD3 in P. falciparum gametocytogenesis. MD3 was originally identified by us as an epigenetically regulated protein of immature gametocytes and recently shown to be involved in male development in a barcode-based screen in P. berghei. We here show that MD3 is mainly present in the cytoplasm of immature male P. falciparum gametocytes. Parasites deficient of MD3 are impaired in gametocyte maturation and male gametocyte exflagellation. BioID analysis in combination with co-immunoprecipitation assays unveiled an interaction network of MD3 with RNA-binding proteins like PABP1 and ALBA3, with translational initiators, regulators and repressors like elF4G, PUF1, NOT1 and CITH, and with other regulators of gametocytogenesis, including ZNF4, MD1 and GD1. We conclude that MD3 is part of a regulator complex crucial for post-transcriptional fine-tuning of male gametocytogenesis.

microbiology↗

bioRxiv2022

Characterization of prohibitins as novel target to block asexual and sexual stage growth of Plasmodium falciparum

Prohibitins (PHBs) are highly conserved pleiotropic proteins as they have been shown to mediate key cellular functions. Here, we characterize PHBs encoding putative genes of Plasmodium falciparum by exploiting different orthologous models. We demonstrated that PfPHB1 (PF3D7_0829200) and PfPHB2 (PF3D7_1014700) are expressed in asexual and sexual blood stages of the parasite. Immunostaining indicated these proteins as mitochondrial residents as they were found to be localized as punctate foci. We further validated PfPHBs as organellar proteins residing in the Plasmodium mitochondria, where they interact with each other. Functional characterization was done in Saccharomyces cerevisiae orthologous model by expressing PfPHB1 and PfPHB2 in cells harboring respective mutants. The PfPHBs functionally complemented the yeast PHB1 and PHB2 mutants, where the proteins were found to be involved in stabilizing the mitochondrial DNA, retaining mitochondrial integrity and rescuing yeast cell growth. Further, Rocaglamide (Roc-A), a known inhibitor of PHBs and anti-cancerous agent, was tested against PfPHBs and as an antimalarial. Roc-A treatment retarded the growth of PHB1, PHB2, and ethidium bromide petite yeast mutants. Moreover, Roc-A inhibited growth of yeast PHBs mutants that were functionally complemented with PfPHBs, validating P. falciparum PHBs as one of the molecular targets for Roc-A. Roc-A treatment led to growth inhibition of artemisinin-sensitive (3D7), artemisinin-resistant (R539T) and chloroquine-resistant (RKL-9) parasites in nanomolar ranges. The compound was able to retard gametocyte growth with significant morphological aberrations. Based on our findings, we propose the presence of functional mitochondrial PfPHB1 and PfPHB2 in P. falciparum and their druggability to block parasite growth.

molecular biology↗