title: Organization of Plasmodium falciparum spliceosomal core complex and role of arginine methylation in its assembly.
abstract: BACKGROUND
  Splicing and alternate splicing are the two key biological processes that result in the generation of diverse transcript and protein isoforms in Plasmodium falciparum as well as in other eukaryotic organisms. Not much is known about the organization of splicing machinery and mechanisms in human malaria parasite. Present study reports the organization and assembly of Plasmodium spliceosome Sm core complex.
  
  
  METHODS
  Presence of all the seven Plasmodium Sm-like proteins in the intra-erythrocytic stages was assessed based on the protein(s) expression analysis using immuno-localization and western blotting. Localization/co-localization studies were performed by immunofluorescence analysis on thin parasite smear using laser scanning confocal microscope. Interaction studies were carried out using yeast two-hybrid analysis and validated by in vitro pull-down assays. PfPRMT5 (arginine methyl transferase) and PfSmD1 interaction analysis was performed by pull-down assays and the interacting proteins were identified by MALDI-TOF spectrometry.
  
  
  RESULTS
  PfSm proteins are expressed at asexual blood stages of the parasite and show nucleo-cytoplasmic localization. Protein-protein interaction studies showed that PfSm proteins form a heptameric complex, typical of spliceosome core complex as shown in humans. Interaction of PfSMN (survival of motor neuron, tudor domain containing protein) or PfTu-TSN (Tudor domain of Tudor Staphylococcal nuclease) with PfSmD1 proteins was found to be methylation dependent. Co-localization by immunofluorescence and co-immunoprecipitation studies suggested an association between PfPRMT5 and PfSmD1, indicating the role of arginine methylation in assembly of Plasmodium spliceosome complex.
  
  
  CONCLUSIONS
  Plasmodium Sm-like proteins form a heptameric ring-like structure, although the arrangement of PfSm proteins slightly differs from human splicing machinery. The data shows the interaction of PfSMN with PfSmD1 and this interaction is found to be methylation dependent. PfPRMT5 probably exists as a part of methylosome complex that may function in the cytoplasmic assembly of Sm proteins at asexual blood stages of P. falciparum.
authors.affiliation: International Centre for Genetic Engineering and Biotechnology, Aruna Asaf Ali Marg, New Delhi 110067, India. pawanmal@gmail.com.
authors.forename: Manzar
authors.initials: M
authors.lastname: Hossain
authors.forename: Shweta
authors.initials: S
authors.lastname: Sharma
authors.forename: Reshma
authors.initials: R
authors.lastname: Korde
authors.forename: Shivani
authors.initials: S
authors.lastname: Kanodia
authors.forename: Monika
authors.initials: M
authors.lastname: Chugh
authors.forename: Khushboo
authors.initials: K
authors.lastname: Rawat
authors.forename: Pawan
authors.initials: P
authors.lastname: Malhotra
mesh_terms: D001120:Arginine / Q000378:metabolism*; D015153:Blotting, Western; D002498:Centrifugation; D008745:Methylation; D018613:Microscopy, Confocal; D008856:Microscopy, Fluorescence; D009097:Multienzyme Complexes / Q000737:chemistry / Q000378:metabolism; D010963:Plasmodium falciparum / Q000737:chemistry* / Q000378:metabolism*; D011485:Protein Binding; D025941:Protein Interaction Mapping; D011499:Protein Processing, Post-Translational; D015800:Protozoan Proteins / Q000378:metabolism*; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D017381:Spliceosomes / Q000737:chemistry* / Q000378:metabolism*; D020798:Two-Hybrid System Techniques
chemical_list: D009097:Multienzyme Complexes; D015800:Protozoan Proteins; D001120:Arginine
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