Abstract
ABSTRACTMalaria parasites need to cope with changing environmental conditions that require strong countermeasures to ensure pathogen survival in the human and mosquito hosts. The molecular mechanisms that protect Plasmodium falciparum homeostasis during the complex life cycle remain unknown. Here, we identify cytosine methylation of tRNAAsp (GTC) as being critical to maintain stable protein synthesis. Using conditional knockout (KO) of a member of the DNA methyltransferase family, called Pf-DNMT2, RNA bisulfite sequencing demonstrated the selective cytosine methylation of this enzyme of tRNAAsp (GTC) at position C38. Although no growth defect on parasite proliferation was observed, Pf-DNMT2KO parasites showed a selective downregulation of proteins with a GAC codon bias. This resulted in a significant shift in parasite metabolism, priming KO parasites for being more sensitive to various types of stress. Importantly, nutritional stress made tRNAAsp (GTC) sensitive to cleavage by an unknown nuclease and increased gametocyte production (>6-fold). Our study uncovers an epitranscriptomic mechanism that safeguards protein translation and homeostasis of sexual commitment in malaria parasites.
Highlights
Malaria parasites need to cope with changing environmental conditions that require strong countermeasures to ensure pathogen survival in the human and mosquito hosts
Given that malaria parasites belong to a small group of DNMT2-only organisms, we generated a Pf-DNMT2 mutant strain to explore its function in this protozoan pathogen
Parasite growth analysis done by measuring DNA content over the course of 4 days showed no significant difference in the asexual growth of DNMT2KO-H9 and -E11 compared to the 3D7-WT control (Fig. 1C)
Summary
Malaria parasites need to cope with changing environmental conditions that require strong countermeasures to ensure pathogen survival in the human and mosquito hosts. Malaria pathogens rely on multiple layers of epigenetics in order to regulate gene expression across their complex life cycle (for review, see reference 2) This fast-evolving research field has recently revealed several unprecedented epigenetic mechanisms in P. falciparum such as histone clipping [3], the role of noncoding RNAs in regulating virulence gene expression and sexual commitment [4, 5] as well as the role of the RNA exosome-linked RNase (Rrp6) in ncRNA decay regulation [6]. It has been shown that similar to the case with other eukaryotes, tRNAs in P. falciparum can be heavily modified and at least 28 different ribonucleoside modifications, including m6A (N6-methyladenosine), m5C (5-methylcytosine), and more complex hypermodifications such as mcm5U (5-methoxycarbonylmethyluridine) and m4Cm (N4,29-O-dimethylcytidine), have been identified These modifications are developmentally regulated across the intraerythrocytic life cycle and have the potential to modulate translation efficiency [11]. The role of the reversible and dynamic tRNA modifications and their corresponding “writers” are a very promising new research field that may unravel missing regulatory mechanisms of malaria parasite stress and disease factors
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