title: Glutamylation of Nap1 modulates histone H1 dynamics and chromosome condensation in Xenopus.
abstract: Linker histone H1 is required for mitotic chromosome architecture in Xenopus laevis egg extracts and, unlike core histones, exhibits rapid turnover on chromatin. Mechanisms regulating the recruitment, deposition, and dynamics of linker histones in mitosis are largely unknown. We found that the cytoplasmic histone chaperone nucleosome assembly protein 1 (Nap1) associates with the embryonic isoform of linker histone H1 (H1M) in egg extracts. Immunodepletion of Nap1 decreased H1M binding to mitotic chromosomes by nearly 50%, reduced H1M dynamics as measured by fluorescence recovery after photobleaching and caused chromosome decondensation similar to the effects of H1M depletion. Defects in H1M dynamics and chromosome condensation were rescued by adding back wild-type Nap1 but not a mutant lacking sites subject to posttranslational modification by glutamylation. Nap1 glutamylation increased the deposition of H1M on sperm nuclei and chromatin-coated beads, indicating that charge-shifting posttranslational modification of Nap1 contributes to H1M dynamics that are essential for higher order chromosome architecture.
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720.
authors.forename: Kelly E
authors.initials: KE
authors.lastname: Miller
authors.affiliation: Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, CA 94720 bheald@berkeley.edu.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Heald
mesh_terms: D000818:Animals; D015153:Blotting, Western; D002467:Cell Nucleus / Q000235:genetics; D002478:Cells, Cultured; D042002:Chromatin Assembly and Disassembly; D002875:Chromosomes / Q000502:physiology*; D003593:Cytoplasm / Q000378:metabolism; D005260:Female; D005455:Fluorescent Antibody Technique; D018698:Glutamic Acid / Q000378:metabolism*; D006657:Histones / Q000378:metabolism*; D047468:Immunoprecipitation; D008938:Mitosis / Q000502:physiology; D056490:Nucleosome Assembly Protein 1 / Q000378:metabolism*; D009865:Oocytes / Q000166:cytology / Q000378:metabolism; D011499:Protein Processing, Post-Translational; D014982:Xenopus laevis / Q000378:metabolism*
chemical_list: D006657:Histones; D056490:Nucleosome Assembly Protein 1; D018698:Glutamic Acid