The multifaceted histone chaperone RbAp46/48 in Plasmodium falciparum: structural insights, production, and characterization

RebL1 is required for macronuclear structure stability and gametogenesis in Tetrahymena thermophila

Histone modification and nucleosome assembly play important roles in chromatin-related processes. Histone chaperones form different complexes and coordinate histone transportation and assembly. Various histone chaperone complexes have been identified in different organisms. The ciliate protozoa (ciliates) have various chromatin structures and different nuclear morphology. However, histone chaperone components and functions of different subunits remain unclear in ciliates. Tetrahymema thermophila contains a transcriptionally active macronucleus (MAC) and a transcriptionally inactive micronucleus (MIC) which exhibit multiple replication and various chromatin remodeling progresses during vegetative growth and sexual developmental stages. Here, we found histone chaperone RebL1 not only localized evenly in the transcriptionally active MAC but also dynamically changed in the MIC during vegetative growth and sexual developmental stages. REBL1 knockdown inhibited cellular proliferation. The macronuclear morphology became bigger in growing mutants. The abnormal macronuclear structure also occurred in the starvation stage. Furthermore, micronuclear meiosis was disturbed during sexual development, leading to a failure to generate new gametic nuclei. RebL1 potentially interacted with various factors involved in histone-modifying complexes and chromatin remodeling complexes in different developmental stages. REBL1 knockdown affected expression levels of the genes involved in chromatin organization and transcription. Taken together, RebL1 plays a vital role in maintaining macronuclear structure stability and gametogenesis in T. thermophila.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-024-00219-z.

The WD40-Protein PfWLP1 Ensures Stability of the PfCCp-Based Adhesion Protein Complex in Plasmodium falciparum Gametocytes

Members of the WD40-repeat protein family can be found in all eukaryotic proteomes where they usually serve as interaction platforms for the assembly of large protein complexes and are therefore essential for the integrity of these complexes. In the malaria parasite Plasmodium falciparum, the WD40-repeat protein PfWLP1 has been shown to interact with members of distinct adhesion protein complexes in the asexual blood stages and gametocyte stages. In this study, we demonstrate that the presence of PfWLP1 is crucial for both the stability of these gametocyte-specific adhesion complexes as well as for gametocyte maturation and gametogenesis. Using reverse genetics, we generated a PfWLP1-knockdown parasite line for functional characterization of the protein. Knockdown of PfWLP1 resulted in a slight reduction of gametocyte numbers and significantly the impaired ability of the gametocytes to exflagellate. PfWLP1-knockdown further led to reduced protein levels of the Limulus coagulation factor C-like (LCCL)-domain proteins PfCCp1 and PfCCp2, which are key components of the adhesion complexes. These findings suggest that the interaction of PfWLP1 with members of the PfCCp-based adhesion complex ensures complex stability and thereby contributes to gametocyte viability and exflagellation.