Biology subjects

Toenhake, C. G.

Publications and source records attributed to Toenhake, C. G..

3 recordsLinked to original sources

bioRxiv2023

Epigenetically-regulated RNA-binding proteins signify malaria hypnozoite dormancy

SUMMARYDormancy enables relapsing malaria parasites, such as Plasmodium vivax and cynomolgi, to survive unfavorable conditions and maximize chances for transmission. It is caused by hypnozoites, parasites remaining quiescent inside hepatocytes before reactivating and establishing blood-stage infection. We integrated various omics approaches to explore gene-regulatory mechanisms underlying hypnozoite formation and reactivation. Genome-wide profiling of epigenetic marks identified a small set of genes that gets epigenetically silenced during hepatic infection of relapsing parasites. Furthermore, by combining single-cell transcriptomics, chromatin accessibility profiling and fluorescent in situ RNA hybridization, we show that these genes are exclusively expressed in hypnozoites and their silencing precedes parasite development. Intriguingly, these hypnozoite-specific genes mainly encode proteins with RNA-binding domains. We, hence, propose that repressive RNA-binding proteins keep hypnozoites in a developmentally competent but dormant state and heterochromatin-mediated silencing of the corresponding genes enables hypnozoite reactivation. Further testing of this hypothesis could provide clues for targeted reactivation and killing of these vicious pathogens.

systems biology↗

bioRxiv2022

Gene-by-gene screen of the unknown proteins encoded on P. falciparum chromosome 3

Taxa-specific proteins are key determinants defining the biology of all organisms and represent prime drug targets in pathogens. However, lacking comparability with proteins in other lineages makes them particularly difficult to study. In malaria parasites this is exacerbated by technical limitations. Here, we analysed the cellular location, essentiality, function and, in selected cases, interactome of all unknown non-secretory proteins encoded on an entire P. falciparum chromosome. The nucleus was the most common localisation, indicating it is a hotspot of parasite-specific biology. More in-depth functional studies with four proteins revealed essential roles in DNA replication and mitosis. The novel mitosis proteins defined a possible orphan complex and a highly diverged complex needed for the spindle-kinetochore connection. Structure-function comparisons indicated that the taxa-specific proteins evolved by different mechanisms. This work demonstrates the feasibility of gene-by-gene screens to elucidate the biology of malaria parasites and reveal critical parasite-specific processes of interest as drug targets.

cell biology↗

bioRxiv2020

The ApiAP2 factor PfAP2-HC is an integral component of heterochromatin in the malaria parasite Plasmodium falciparum

Malaria parasites undergo a highly complex life cycle in the human host and the mosquito vector. The ApiAP2 family of sequence-specific DNA-binding proteins plays a dominant role in parasite development and life cycle progression. Of the ApiAP2 factors studied to date, most act as transcription factors regulating stage-specific gene expression. Here, we characterised a new ApiAP2 factor in Plasmodium falciparum (PF3D7_1456000) that we termed PfAP2-HC. Via detailed investigation of several single or double genetically engineered parasite lines, we demonstrate that PfAP2-HC specifically binds to heterochromatin throughout the genome. Intriguingly, PfAP2-HC does not bind DNA in vivo and recruitment of PfAP2-HC to heterochromatin is independent of its DNA-binding domain but strictly dependent on heterochromatin protein 1. Furthermore, our results suggest that PfAP2-HC functions neither in the regulation of gene expression nor in heterochromatin formation or maintenance. In summary, our findings reveal that PfAP2-HC constitutes a core component of heterochromatin in malaria parasites. They furthermore identify unexpected properties of ApiAP2 factors and suggest substantial functional divergence among the members of this important family of regulatory proteins.

microbiology↗