Nucleosome assembly protein-1 is a linker histone chaperone in Xenopus eggs.
In eukaryotic cells, genomic DNA is primarily packaged into nucleosomes through sequential ordered binding of the core and linker histone proteins. The acidic proteins termed histone chaperones are known to bind to core histones to neutralize their positive charges, thereby facilitating their proper deposition onto DNA to assemble the core of nucleosomes. For linker histones, however, little has been known about the regulatory mechanism for deposition of linker histones onto the linker DNA. Here we report that, in Xenopus eggs, the linker histone is associated with the Xenopus homologue of nucleosome assembly protein-1 (NAP-1), which is known to be a chaperone for the core histones H2A and H2B in Drosophila and mammalian cells [Ito, T., Bulger, M., Kobayashi, R. & Kadonaga, J. T. (1996) Mol. Cell Biol. 16, 3112-3124; Chang, L., Loranger, S. S., Mizzen, C., Ernst, S. G., Allis, C. D. & Annunziato, A. T. (1997) Biochemistry 36, 469-480]. We show that NAP-1 acts as the chaperone for the linker histone in both sperm chromatin remodeling into nucleosomes and linker histone binding to nucleosome core dimers. In the presence of NAP-1, the linker histone is properly deposited onto linker DNA at physiological ionic strength, without formation of nonspecific aggregates. These results strongly suggest that NAP-1 functions as a chaperone for the linker histone in Xenopus eggs.
Shintomi
Keishi
K
Laboratory of Cell and Developmental Biology, Graduate School of Bioscience and Biotechnology, Tokyo Institute of Technology, 4259 Nagatsuta, Midori-ku, Yokohama 226-8501, Japan. kohsumi@bio.titech.ac.jp
Iwabuchi
Mari
M
Saeki
Hideaki
H
Ura
Kiyoe
K
Kishimoto
Takeo
T
Ohsumi
Keita
K
D000595:Amino Acid Sequence; D000818:Animals; D018797:Cell Cycle Proteins; D002457:Cell Extracts; D042002:Chromatin Assembly and Disassembly; D029721:Drosophila Proteins; D005260:Female; D006657:Histones / Q000378:metabolism*; D008297:Male; D018832:Molecular Chaperones / Q000378:metabolism*; D008969:Molecular Sequence Data; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D009707:Nucleosomes / Q000737:chemistry / Q000378:metabolism*; D009865:Oocytes / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D013094:Spermatozoa / Q000378:metabolism; D014981:Xenopus / Q000378:metabolism*
D018797:Cell Cycle Proteins; D002457:Cell Extracts; D029721:Drosophila Proteins; D006657:Histones; D018832:Molecular Chaperones; C533554:Nap1 protein, Drosophila; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D009707:Nucleosomes; D011506:Proteins