Unveiling the architecture of the histone chaperone nucleoplasmin from the malarial parasite

Research Summary: We elucidated the structure and function of PfNPM, a putative histone chaperone from the malarial parasite Plasmodium falciparum, revealing architecture, histone interactions, and potential role in transcription regulation.

Author interview: Dr Ketul Saharan earned his PhD from BRIC-ILS Bhubaneswar with a specialization in structural biology and biochemistry. He is currently a postdoctoral research associate at the University of Cambridge.

LinkedIn: https://www.linkedin.com/in/ketul-saharan-73807b159/

Twitter: https://x.com/SaharanKetul

Lab: Dr. Dileep Vasudevan, BRIC-Rajiv Gandhi Centre for Biotechnology (BRIC-RGCB), Thiruvananthapuram

Previous affiliation: BRIC-Institute of Life Sciences (BRIC-ILS), Bhubaneswar

Lab website: https://dvasulab.com/

Lab’s Twitter: https://x.com/lab_vasu

What was the core problem you aimed to solve with this research?

Our study was driven by a desire to expand basic scientific knowledge about malarial parasite Plasmodium falciparum biology. While nucleoplasmins are well-characterized in other eukaryotic systems, their presence and role in this parasite remained a complete mystery. We sought to address the knowledge gap regarding the presence and characteristics of a nucleoplasmin isoform from Plasmodium falciparum. Our core problem was to explore the fundamental structural and functional aspects of PfNPM, contributing to a better understanding of the parasite’s chromatin regulation.

How did you go about solving this problem?

We employed an integrative approach, combining structural biology, biochemical, and cell biology techniques. First, we determined the crystal structure of PfNPM to visualize its 3D architecture, confirming the expected pentameric structure. We then used biochemical assays, including Electrophoretic Mobility Shift Assay (EMSA), Pull-Down and Isothermal Titration Calorimetry (ITC), to study its interactions with histones H2A/H2B and H3/H4. To confirm the oligomeric status of the protein in solution, we used AUC, SAXS and Cryo-EM. Finally, we used immunofluorescence microscopy to investigate its localization and expression pattern within the blood stages of the parasite.

We add a new member to the nucleoplasmin family of histone chaperones, this time from the malarial parasite Plasmodium falciparum.

How would you explain your research outcomes (Key findings) to the non-scientific community?

To understand how the malaria parasite manages its DNA, we studied a protein named PfNPM. Think of DNA as a very long piece of string. This string needs to be neatly organized to fit inside the tiny space of the cell’s nucleus. To do this, the DNA string is wrapped around histone protein ‘spools’, together forming a ‘beads on a string’ organization within the nucleus of the parasite. These histone proteins that form the spool for the DNA to wrap around are brought to the nucleus by proteins called histone chaperones, and PfNPM was thought to be one such chaperone, which we have studied in this work. We discovered that PfNPM has a distinct donut-like shape and interacts with these histone proteins, aiding their transport to the nucleus. We also found that PfNPM is expressed primarily during the early stages of the parasite’s life cycle and is located in the nucleus, where the parasite’s DNA resides. This gives us crucial insights into how the parasite handles its fundamental genetic processes that are based on DNA packaging and unwrapping.

What are the potential implications of your findings for the field and society?

Our findings have significant implications for both the scientific community and society. By characterizing PfNPM, we have significantly expanded our understanding of how this essential protein contributes to the parasite’s biology. This advances our understanding of the complex processes that govern gene expression during the parasite’s early developmental stages. For the scientific community, the in vitro observations regarding histone interactions of PfNPM, the correlated expression of PfNPM with the transcription factor FACT, and the sequence similarity of PfNPM with a Toxoplasma gondii protein named Nuclear Factor 3 (TgNF3) raise intriguing questions about the functional intricacies of this family of proteins across apicomplexan parasites to which both Plasmodium and Toxoplasma belong. This opens up avenues for further investigation into the fundamental processes that govern the life cycle of parasites. A basic understanding of the biology of the parasites, such as the one from this work, is definitely the way forward to come up with efficient strategies to combat the parasite disease burden, more so because these parasites have lately started becoming resistant to the available drugs.

What was the exciting moment during your research?

The most exciting moment was when we obtained the crystal structure and confirmed the characteristic pentameric donut shape of PfNPM. Seeing the solution structure, which double confirmed the pentameric organization of the protein, was also very exciting. Together, these observations validated our hypotheses and provided a visual representation of its architecture, which was crucial for understanding its function.

Reference: Ketul Saharan, Somanath Baral, Surajit Gandhi, Ajit K. Singh, Sourav Ghosh, Rahul Das, Viswanathan A. Nagaraj, Dileep Vasudevan. 2025. Structure-function studies of a nucleoplasmin isoform from Plasmodium falciparum. Journal of Biological Chemistry 108379. DOI: 10.1016/j.jbc.2025.108379. https://www.jbc.org/article/S0021-9258(25)00228-5/fulltext

🎯 Hire the Best Talent in Life Sciences & STEM

Are you hiring for internships, PhDs, postdocs, faculty, or biotech jobs? Promote your openings on our platform to reach thousands of passionate students, researchers, and professionals in life sciences, biotech, pharma, and STEM.

📢 Promote with Us