The Plasmodium falciparum histone methyltransferase SET10 participates in a chromatin modulation network crucial for intraerythrocytic development

The 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 an H3K4 methyltransferase involved in var gene regulation, making it a prominent antimalarial target. In this study, we investigated 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 reduces intraerythrocytic growth but has no effect on gametocyte commitment and maturation. Screening of the PfSET10-KO line for histone methylation variations reveals that lack of PfSET10 renders the parasites unable to mark H3K18me1, while no reduction in the H3K4 methylation status could be observed. Comparative transcriptomic profiling of PfSET10-KO schizonts shows an upregulation of transcripts particularly encoding proteins linked to red blood cell remodeling and antigenic variation, suggesting a repressive function of the histone methylation mark. TurboID coupled with mass spectrometry further highlights an extensive nuclear PfSET10 interaction network with roles in transcriptional regulation and mRNA processing, DNA replication and repair, and chromatin remodeling. The main interactors of PfSET10 include ApiAP2 transcription factors, epigenetic regulators like PfHDAC1, chromatin modulators like PfMORC and PfISWI, mediators of RNA polymerase II, and DNA replication licensing factors. The combined data pinpoint PfSET10 as a histone methyltransferase essential for H3K18 methylation that regulates nucleic acid metabolic processes in the P. falciparum blood stages 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 promotes the methylation of 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 methyltransferase affecting H3K18 methylation with critical functions in chromatin maintenance during the development of P. falciparum in red blood cells.

IMMUNOLOGICAL PROFILES IN HIV POSITIVE PATIENTS FOLLOWING HAART INITIATION IN KIGALI, RWANDA

BACKGROUND

Interleukin-10, IL-2 and IFN-γ are some of the crucial cytokines associated with HIV infection and pathogenesis. While IL-2 and IFN-γ play critical roles in host resistance to infection, IL-10 inhibits the synthesis IFN-γ, IL-2 at mRNA and protein level; exacerbating damage to immune system.

OBJECTIVE

To determine the levels of, changes in and correlation between CD4 count, viral load, IL-10, IL-2 and IFN-γ before HAART and at six months of HAART among HIV positive patients in Kigali; with a view to understand cytokine networks particularly in relation to HAART; and to see whether they can be used as alternative markers of the disease progression.

DESIGN

Longitudinal study.

SETTING

Kagugu, Kimironko, Biryogo, Gitega Health Centres and Centre Medico-Social Cornum; all located in Kigali.

SUBJECTS

Thirty three (33) HAART initiation eligible HIV positive patients including 13 women and 20 men.

RESULTS

A drop in viral load (though only a small number of patients achieved an undetectable viraemia); a recovery of CD4+ cells, a decrease in IL-10 (though it remained high for many patients especially those with unchanged viraemia); and an increase in IL-2 and IFN-γ indicated a successful HAART. A negative correlation between CD4 count and viral load and between CD4 count and IL-10 (but r < -0.5) was observed. IL-10 correlated positively and strongly with viremia (r > 0.5 at both time points: p-values < 0.05). There was no significant correlation between CD4 count, IL-2 and IFN-y.

CONCLUSION

Results demonstrated the down-regulatory effect of IL-10 on Th1 cytokines and that a shift from Th1 to Th2 cytokine is associated with HIV disease progression. A successful HAART results in CD4+ cells recovery, drop in viraemia and IL-10 with up-regulation of Th1 cytokines. Also, findings show potential usefulness of IL-10 as a marker of HIV disease progression.