Condensin I binds chromatin early in prophase and displays a highly dynamic association with <Emphasis Type="Italic">Drosophila</Emphasis> mitotic chromosomes |
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Authors: | Raquel A Oliveira Stefan Heidmann Claudio E Sunkel |
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Institution: | (1) Instituto de Biologia Molecular e Celular, Universidade do Porto, Rua do Campo Alegre 823, 4150-180 Porto, Portugal;(2) Programa Doutoral em Biologia Experimental e Biomedicina (PDBEB), Center for Neuroscience and Cell Biology, University of Coimbra, Coimbra, Portugal;(3) Department of Genetics, Bayreuth Center for Molecular Biosciences (BZMB), University of Bayreuth, Bayreuth, Germany;(4) Instituto de Ciências Biomédicas Abel Salazar (ICBAS), Universidade do Porto, Largo do Prof. Abel Salazar 4000, Porto, Portugal |
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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.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. |
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