RRM2 of CELF1 Protein from Plasmodium falciparum Preferentially Binds to UG Repeats RNA

Abstract

Malaria causes high mortality (∼445,000 casualties) despite continued efforts for its eradication. Plasmodium falciparum is the prime cause of lethal malaria in human. In spite of having a small genome, it exemplifies a vast proteome, which leads to its widespread resistance against various anti-malarial drugs. The process of alternative splicing is mostly responsible for this proteomic diversity. CELF (CUGBP Elav like family member) proteins play an active role in pre-mRNA alternative splicing, translational regulation, de-adenylation, mRNA stability and RNA editing among various eukaryotes. PfCELF (P. falciparum CELF) has three RNA recognition motifs (RRMs), of which second and third are separated by a WW domain. To understand the molecular basis of RNA recognition by PfCELF we have undertaken extensive structural and biochemical studies. We have completed the sequence-specific NMR resonance assignment of RRM2 of PfCELF and the initial model generated using torsion angles derived from chemical shift shows it of having a characteristic β-α-β-β-α-β fold. Our calorimetric studies and NMR titration show that PfCELF-RRM2 has a strong affinity towards UG repeats RNA that possibly interact in a canonical manner. We have also prepared selenomethionine-enriched crystals of this protein and collected X-ray diffraction data at 2.2Å resolution.