title: Condensin I binds chromatin early in prophase and displays a highly dynamic association with Drosophila mitotic chromosomes.
abstract: The condensed state of mitotic chromosomes is crucial for faithful genome segregation. Key factors implicated in the formation of mitotic chromosomes are the condensin I and II complexes. In Drosophila, condensin I appears to play a major role in mitotic chromosome organization. To analyze its dynamic behavior, we expressed Barren, a condensin I non-Structural Maintenance of Chromosomes subunit, as a fully functional enhanced green fluorescent protein (EGFP) fusion protein in the female and followed it during early embryonic divisions. We find that, in Drosophila, Barren-EGFP associates with chromatin early in prophase concomitantly with the initiation of chromosome condensation. Barren-EGFP loading starts at the centromeric region from where it spreads distally reaching maximum accumulation at metaphase/early anaphase. Fluorescence Recovery After Photobleaching analysis indicates that most of the bound protein exchanges rapidly with the cytoplasmic pool during prometaphase/metaphase. Taken together, our results suggest that in Drosophila, condensin I is involved in the initial stages of chromosome condensation. Furthermore, the rapid turnover of Barren-EGFP indicates that the mechanism by which condensin I promotes mitotic chromosome organization is inconsistent with a static scaffold model.
authors.affiliation: Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal.
authors.forename: Raquel A
authors.initials: RA
authors.lastname: Oliveira
authors.forename: Stefan
authors.initials: S
authors.lastname: Heidmann
authors.forename: Claudio E
authors.initials: CE
authors.lastname: Sunkel
mesh_terms: D000251:Adenosine Triphosphatases / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D002843:Chromatin / Q000378:metabolism*; D002875:Chromosomes / Q000378:metabolism* / Q000648:ultrastructure; D004268:DNA-Binding Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000737:chemistry / Q000196:embryology* / Q000235:genetics; D029721:Drosophila Proteins / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000032:analysis / Q000235:genetics; D008938:Mitosis; D046912:Multiprotein Complexes / Q000032:analysis / Q000235:genetics / Q000378:metabolism*; D011418:Prophase
chemical_list: C103227:Barr protein, Drosophila; D018797:Cell Cycle Proteins; D002843:Chromatin; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D046912:Multiprotein Complexes; C108312:condensin complexes; C485184:enhanced green fluorescent protein; D049452:Green Fluorescent Proteins; D000251:Adenosine Triphosphatases