sNASP, a histone H1-specific eukaryotic chaperone dimer that facilitates chromatin assembly.
NASP has been described as a histone H1 chaperone in mammals. However, the molecular mechanisms involved have not yet been characterized. Here, we show that this protein is not only present in mammals but is widely distributed throughout eukaryotes both in its somatic and testicular forms. The secondary structure of the human somatic version consists mainly of clusters of alpha-helices and exists as a homodimer in solution. The protein binds nonspecifically to core histone H2A-H2B dimers and H3-H4 tetramers but only forms specific complexes with histone H1. The formation of the NASP-H1 complexes is mediated by the N- and C-terminal domains of histone H1 and does not involve the winged helix domain that is characteristic of linker histones. In vitro chromatin reconstitution experiments show that this protein facilitates the incorporation of linker histones onto nucleosome arrays and hence is a bona fide linker histone chaperone.
Finn
Ron M
RM
Department of Biochemistry and Microbiology, University of Victoria, Petch Building, Victoria, BC V8W 3P6, Canada.
Browne
Kristen
K
Hodgson
Kim C
KC
Ausió
Juan
J
D000818:Animals; D001324:Autoantigens / Q000737:chemistry* / Q000648:ultrastructure*; D001665:Binding Sites; D002843:Chromatin / Q000737:chemistry* / Q000648:ultrastructure*; D042002:Chromatin Assembly and Disassembly; D003198:Computer Simulation; D003432:Cross-Linking Reagents / Q000737:chemistry; D019281:Dimerization; D005057:Eukaryotic Cells; D006657:Histones / Q000737:chemistry* / Q000648:ultrastructure*; D006801:Humans; D008956:Models, Chemical; D008958:Models, Molecular; D018832:Molecular Chaperones / Q000737:chemistry / Q000648:ultrastructure; D009687:Nuclear Proteins / Q000737:chemistry* / Q000648:ultrastructure*; D011485:Protein Binding
D001324:Autoantigens; D002843:Chromatin; D003432:Cross-Linking Reagents; D006657:Histones; D018832:Molecular Chaperones; C489390:NASP protein, human; D009687:Nuclear Proteins