title: CAF-1 is required for efficient replication of euchromatic DNA in Drosophila larval endocycling cells.
abstract: The endocycle constitutes an effective strategy for cell growth during development. In contrast to the mitotic cycle, it consists of multiple S-phases with no intervening mitosis and lacks a checkpoint ensuring the replication of the entire genome. Here, we report an essential requirement of chromatin assembly factor-1 (CAF-1) for Drosophila larval endocycles. This complex promotes histone H3-H4 deposition onto newly synthesised DNA in vitro. In metazoans, the depletion of its large subunit leads to the rapid accumulation of cells in S-phase. However, whether this slower S-phase progression results from the activation of cell cycle checkpoints or whether it reflects a more direct requirement of CAF-1 for efficient replication in vivo is still debated. Here, we show that, strikingly, Drosophila larval endocycling cells depleted for the CAF-1 large subunit exhibit normal dynamics of progression through endocycles, although accumulating defects, such as perturbation of nucleosomal organisation, reduction of the replication efficiency of euchromatic DNA and accumulation of DNA damage. Given that the endocycle lacks a checkpoint ensuring the replication of the entire genome, the biological context of Drosophila larval development offered a unique opportunity to highlight the requirement of CAF-1 for chromatin organisation and efficient replication processes in vivo, independently of checkpoint activation.
authors.affiliation: CNRS, Institut Curie, Pavillon Pasteur, Paris, France.
authors.forename: Benjamin
authors.initials: B
authors.lastname: Klapholz
authors.forename: Bruce H
authors.initials: BH
authors.lastname: Dietrich
authors.forename: Catherine
authors.initials: C
authors.lastname: Schaffner
authors.forename: Fabiana
authors.initials: F
authors.lastname: Hérédia
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Quivy
authors.forename: Geneviève
authors.initials: G
authors.lastname: Almouzni
authors.forename: Nathalie
authors.initials: N
authors.lastname: Dostatni
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D001483:Base Sequence; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D002868:Chromosomal Proteins, Non-Histone / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D004247:DNA / Q000235:genetics; D004249:DNA Damage; D004261:DNA Replication / Q000502:physiology*; D004330:Drosophila / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*; D022041:Euchromatin / Q000378:metabolism*; D005260:Female; D017344:Genes, Insect; D049750:Genome, Insect; D007814:Larva / Q000166:cytology / Q000378:metabolism; D008297:Male; D018832:Molecular Chaperones / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D009707:Nucleosomes / Q000235:genetics / Q000378:metabolism; D021122:Protein Subunits; D056505:Retinoblastoma-Binding Protein 4; D016196:S Phase; D012469:Salivary Glands / Q000166:cytology / Q000378:metabolism
chemical_list: C110251:Caf1-55 protein, Drosophila; D018797:Cell Cycle Proteins; D002868:Chromosomal Proteins, Non-Histone; D029721:Drosophila Proteins; D022041:Euchromatin; D018832:Molecular Chaperones; D009707:Nucleosomes; D021122:Protein Subunits; D056505:Retinoblastoma-Binding Protein 4; C491642:asf1 protein, Drosophila; D004247:DNA