title: The condensin I subunit Barren/CAP-H is essential for the structural integrity of centromeric heterochromatin during mitosis.
abstract: During cell division, chromatin undergoes structural changes essential to ensure faithful segregation of the genome. Condensins, abundant components of mitotic chromosomes, are known to form two different complexes, condensins I and II. To further examine the role of condensin I in chromosome structure and in particular in centromere organization, we depleted from S2 cells the Drosophila CAP-H homologue Barren, a subunit exclusively associated with condensin I. In the absence of Barren/CAP-H the condensin core subunits DmSMC4/2 still associate with chromatin, while the other condensin I non-structural maintenance of chromosomes family proteins do not. Immunofluorescence and in vivo analysis of Barren/CAP-H-depleted cells showed that mitotic chromosomes are able to condense but fail to resolve sister chromatids. Additionally, Barren/CAP-H-depleted cells show chromosome congression defects that do not appear to be due to abnormal kinetochore-microtubule interaction. Instead, the centromeric and pericentromeric heterochromatin of Barren/CAP-H-depleted chromosomes shows structural problems. After bipolar attachment, the centromeric heterochromatin organized in the absence of Barren/CAP-H cannot withstand the forces exerted by the mitotic spindle and undergoes irreversible distortion. Taken together, our data suggest that the condensin I complex is required not only to promote sister chromatid resolution but also to maintain the structural integrity of centromeric heterochromatin during mitosis.
authors.affiliation: Instituto de Biologia Molecular e Celular, Universidade do Porto, Portugal.
authors.forename: Raquel A
authors.initials: RA
authors.lastname: Oliveira
authors.forename: Paula A
authors.initials: PA
authors.lastname: Coelho
authors.forename: Claudio E
authors.initials: CE
authors.lastname: Sunkel
mesh_terms: D000251:Adenosine Triphosphatases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D018797:Cell Cycle Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D002503:Centromere / Q000378:metabolism*; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D004330:Drosophila / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017344:Genes, Insect; D006570:Heterochromatin / Q000378:metabolism*; D018386:Kinetochores / Q000378:metabolism; D008938:Mitosis / Q000235:genetics / Q000502:physiology*; D046912:Multiprotein Complexes / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D021122:Protein Subunits; D034622:RNA Interference
chemical_list: C103227:Barr protein, Drosophila; D018797:Cell Cycle Proteins; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D006570:Heterochromatin; D046912:Multiprotein Complexes; D021122:Protein Subunits; C108312:condensin complexes; D000251:Adenosine Triphosphatases