The Two Plasmodium falciparum Nucleosome Assembly Proteins Play Distinct Roles in Histone Transport and Chromatin Assembly

Vasundhara M Navadgi,Amit Sharma,Prakash Chandra Mishra,Beeram Ravi Chandra

doi:10.1074/jbc.m602243200

Vasundhara M Navadgi, Amit Sharma + Show 2 more

Open Access

https://doi.org/10.1074/jbc.m602243200

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Abstract

The malarial parasite Plasmodium falciparum has two nucleosome assembly proteins, PfNapS and PfNapL (Chandra, B. R., Olivieri, A., Silvestrini, F., Alano, P., and Sharma, A. (2005) Mol. Biochem. Parasitol. 142, 237-247). We show that both PfNapS and PfNapL interact with histone oligomers but only PfNapS is able to deposit histones onto DNA. This property of PfNapS is divalent cation-dependent and ATP-independent. Deletion of the terminal subdomains of PfNapS abolishes its nucleosome assembly capabilities, but the truncated protein retains its ability to bind histones. Both PfNapS and PfNapL show binding to the linker histone H1 suggesting their probable role in extraction of H1 from chromatin fibers. Our data suggests distinct sites of interaction for H1 versus H3/H4 on PfNapS. We show that PfNapS and PfNapL are phosphorylated both in vivo and in vitro by casein kinase-II, and this modification is specifically inhibited by heparin. Circular dichroism, fluorescence spectroscopy, and chymotrypsin fingerprinting data together suggest that PfNapL may undergo very small and subtle structural changes upon phosphorylation. Specifically, phosphorylation of PfNapL increases its affinity 3-fold for core histones H3, H4, and for the linker histone H1. Finally, we demonstrate that PfNapS is able to extract histones from both phosphorylated and unphosphorylated PfNapL, potentially for histone deposition onto DNA. Based on these results, we suggest that the P. falciparum NapL is involved in the nucleocytoplasmic relay of histones, whereas PfNapS is likely to be an integral part of the chromatin assembly motors in the parasite nucleus.

Highlights

The major players in this process include multisubunit chromatin remodeling enzymes, histone-modifying enzymes, and histone chaperones [5,6,7,8,9]
Nucleosome assembly protein (Nap), chromatin assembly factor-1 (CAF-1), antisilencing function-1 (Asf1), and histone regulatory protein A (HirA) are histone chaperones that are involved in the deposition of core histones onto DNA (10 –13)
Our current studies indicate that PfNapS is phosphorylated both in vivo and in vitro by casein kinase-II, and this modification is inhibited by heparin, a specific inhibitor for CK-II

Summary

Introduction

The major players in this process include multisubunit chromatin remodeling enzymes, histone-modifying enzymes, and histone chaperones [5,6,7,8,9]. Native gels and ELISA4-based assays indicate that DNA is able to compete with the interaction of PfNapS and PfNapL with core histones. Plasmid supercoiling assays suggest that PfNapS is able to deposit histones onto DNA, whereas PfNapL is not.

Results

Conclusion