Linker histone variants control chromatin dynamics during early embryogenesis.
Complex transitions in chromatin structure produce changes in genome function during development in metazoa. Linker histones, the last component of nucleosomes to be assembled into chromatin, comprise considerably divergent subtypes as compared with core histones. In all metazoa studied, their composition changes dramatically during early embryogenesis concomitant with zygotic gene activation, leading to distinct functional changes that are still poorly understood. Here, we show that early embryonic linker histone B4, which is maternally expressed, is functionally different from somatic histone H1 in influencing chromatin structure and dynamics. We developed a chromatin assembly system with nucleosome assembly protein-1 as a linker histone chaperone. This assay system revealed that maternal histone B4 allows chromatin to be remodeled by ATP-dependent chromatin remodeling factor, whereas somatic histone H1 prevents this remodeling. Structural analysis shows that histone B4 does not significantly restrict the accessibility of linker DNA. These findings define the functional significance of developmental changes in linker histone variants. We propose a model that holds that maternally expressed linker histones are key molecules specifying nuclear dynamics with respect to embryonic totipotency.
Saeki
Hideaki
H
Division of Gene Therapy Science, Osaka University Graduate School of Medicine, 2-2 Yamada-oka, Suita, Osaka 565-0871, Japan.
Ohsumi
Keita
K
Aihara
Hitoshi
H
Ito
Takashi
T
Hirose
Susumu
S
Ura
Kiyoe
K
Kaneda
Yasufumi
Y
D000818:Animals; D018797:Cell Cycle Proteins; D002843:Chromatin / Q000378:metabolism*; D047108:Embryonic Development / Q000235:genetics*; D006367:HeLa Cells; D006657:Histones / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D018832:Molecular Chaperones / Q000235:genetics / Q000378:metabolism; D009687:Nuclear Proteins; D009690:Nucleic Acid Conformation; D056490:Nucleosome Assembly Protein 1; D011506:Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism; D014982:Xenopus laevis / Q000196:embryology / Q000378:metabolism
D018797:Cell Cycle Proteins; D002843:Chromatin; D006657:Histones; D018832:Molecular Chaperones; C533557:NAP1L1 protein, human; D009687:Nuclear Proteins; D056490:Nucleosome Assembly Protein 1; D011506:Proteins; D011994:Recombinant Proteins; D029867:Xenopus Proteins