title: Modulation of histone deposition by the karyopherin kap114.
abstract: The nuclear import of histones is a prerequisite for the downstream deposition of histones to form chromatin. However, the coordinate regulation of these processes remains poorly understood. Here we demonstrate that Kap114p, the primary karyopherin/importin responsible for the nuclear import of histones H2A and H2B, modulates the deposition of histones H2A and H2B by the histone chaperone Nap1p. We show that a complex comprising Kap114p, histones H2A and H2B, and Nap1p is present in the nucleus and that the presence of this complex is specifically promoted by Nap1p. This places Kap114p in a position to modulate Nap1p function, and we demonstrate by the use of two different assay systems that Kap114p inhibits Nap1p-mediated chromatin assembly. The inhibition of H2A and H2B deposition by Kap114p results in the concomitant inhibition of RCC1 loading onto chromatin. Biochemical evidence suggests that the mechanism by which Kap114p modulates histone deposition primarily involves direct histone binding, while the interaction between Kap114p and Nap1p plays a secondary role. Furthermore, we found that the inhibition of histone deposition by Kap114p is partially reversed by RanGTP. Our results indicate a novel mechanism by which cells can regulate histone deposition and establish a coordinate link between histone nuclear import and chromatin assembly.
authors.affiliation: Center for Cell Signaling, University of Virginia HSC, Box 800577, Charlottesville, VA 22908, USA.
authors.forename: Nima
authors.initials: N
authors.lastname: Mosammaparast
authors.forename: Brian C
authors.initials: BC
authors.lastname: Del Rosario
authors.forename: Lucy F
authors.initials: LF
authors.lastname: Pemberton
mesh_terms: D000818:Animals; D018797:Cell Cycle Proteins; D002467:Cell Nucleus / Q000737:chemistry / Q000378:metabolism; D002843:Chromatin / Q000737:chemistry / Q000378:metabolism; D006657:Histones / Q000037:antagonists & inhibitors / Q000378:metabolism*; D028884:Karyopherins / Q000502:physiology*; D008297:Male; D008954:Models, Biological; D009687:Nuclear Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D056490:Nucleosome Assembly Protein 1; D017354:Point Mutation / Q000235:genetics; D025941:Protein Interaction Mapping; D017434:Protein Structure, Tertiary / Q000502:physiology; D011506:Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D012441:Saccharomyces cerevisiae / Q000502:physiology; D029701:Saccharomyces cerevisiae Proteins / Q000032:analysis / Q000378:metabolism / Q000502:physiology*; D013094:Spermatozoa / Q000737:chemistry; D014982:Xenopus laevis; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein / Q000235:genetics / Q000502:physiology
chemical_list: D018797:Cell Cycle Proteins; D002843:Chromatin; D006657:Histones; C400425:KAP114 protein, S cerevisiae; D028884:Karyopherins; C533556:NAP1 protein, S cerevisiae; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D011506:Proteins; D029701:Saccharomyces cerevisiae Proteins; D028961:beta Karyopherins; D020931:ran GTP-Binding Protein