title: Involvement of Plasmodium falciparum protein kinase CK2 in the chromatin assembly pathway.
abstract: BACKGROUND
  Protein kinase CK2 is a pleiotropic serine/threonine protein kinase with hundreds of reported substrates, and plays an important role in a number of cellular processes. The cellular functions of Plasmodium falciparum CK2 (PfCK2) are unknown. The parasite's genome encodes one catalytic subunit, PfCK2α, which we have previously shown to be essential for completion of the asexual erythrocytic cycle, and two putative regulatory subunits, PfCK2β1 and PfCK2β2.
  
  
  RESULTS
  We now show that the genes encoding both regulatory PfCK2 subunits (PfCK2β1 and PfCK2β2) cannot be disrupted. Using immunofluorescence and electron microscopy, we examined the intra-erythrocytic stages of transgenic parasite lines expressing hemagglutinin (HA)-tagged catalytic and regulatory subunits (HA-CK2α, HA-PfCK2β1 or HA-PfCK2β2), and localized all three subunits to both cytoplasmic and nuclear compartments of the parasite. The same transgenic parasite lines were used to purify PfCK2β1- and PfCK2β2-containing complexes, which were analyzed by mass spectrometry. The recovered proteins were unevenly distributed between various pathways, with a large proportion of components of the chromatin assembly pathway being present in both PfCK2β1 and PfCK2β2 precipitates, implicating PfCK2 in chromatin dynamics. We also found that chromatin-related substrates such as nucleosome assembly proteins (Naps), histones, and two members of the Alba family are phosphorylated by PfCK2α in vitro.
  
  
  CONCLUSIONS
  Our reverse-genetics data show that each of the two regulatory PfCK2 subunits is required for completion of the asexual erythrocytic cycle. Our interactome study points to an implication of PfCK2 in many cellular pathways, with chromatin dynamics being identified as a major process regulated by PfCK2. This study paves the way for a kinome-wide interactomics-based approach to elucidate protein kinase function in malaria parasites.
authors.affiliation: Biology of Host-Parasite Interactions Unit, Institut Pasteur, 25 rue du Dr. Roux, F-75724 Paris, France.
authors.forename: Eeshita G
authors.initials: EG
authors.lastname: Dastidar
authors.forename: Guillem
authors.initials: G
authors.lastname: Dayer
authors.forename: Zoe M
authors.initials: ZM
authors.lastname: Holland
authors.forename: Dominique
authors.initials: D
authors.lastname: Dorin-Semblat
authors.forename: Aurélie
authors.initials: A
authors.lastname: Claes
authors.forename: Arnaud
authors.initials: A
authors.lastname: Chêne
authors.forename: Amit
authors.initials: A
authors.lastname: Sharma
authors.forename: Romain
authors.initials: R
authors.lastname: Hamelin
authors.forename: Marc
authors.initials: M
authors.lastname: Moniatte
authors.forename: Jose-Juan
authors.initials: JJ
authors.lastname: Lopez-Rubio
authors.forename: Artur
authors.initials: A
authors.lastname: Scherf
authors.forename: Christian
authors.initials: C
authors.lastname: Doerig
mesh_terms: D047390:Casein Kinase II / Q000235:genetics / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D042002:Chromatin Assembly and Disassembly; D005786:Gene Expression Regulation; D006388:Hemagglutinins / Q000737:chemistry; D056488:Histone Chaperones / Q000378:metabolism; D006657:Histones / Q000378:metabolism; D013058:Mass Spectrometry; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence; D010766:Phosphorylation; D010963:Plasmodium falciparum / Q000201:enzymology / Q000254:growth & development / Q000378:metabolism*; D015800:Protozoan Proteins / Q000378:metabolism*
chemical_list: D002843:Chromatin; D006388:Hemagglutinins; D056488:Histone Chaperones; D006657:Histones; D015800:Protozoan Proteins; D047390:Casein Kinase II