Mitotic chromosome condensation requires Brn1p, the yeast homologue of Barren.
In vitro studies suggest that the Barren protein may function as an activator of DNA topoisomerase II and/or as a component of the Xenopus condensin complex. To better understand the role of Barren in vivo, we generated conditional alleles of the structural gene for Barren (BRN1) in Saccharomyces cerevisiae. We show that Barren is an essential protein required for chromosome condensation in vivo and that it is likely to function as an intrinsic component of the yeast condensation machinery. Consistent with this view, we show that Barren performs an essential function during a period of the cell cycle when chromosome condensation is established and maintained. In contrast, Barren does not serve as an essential activator of DNA topoisomerase II in vivo. Finally, brn1 mutants display additional phenotypes such as stretched chromosomes, aberrant anaphase spindles, and the accumulation of cells with >2C DNA content, suggesting that Barren function influences multiple aspects of chromosome transmission and dynamics.
Lavoie
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Department of Embryology, Howard Hughes Medical Institute, Carnegie Institution of Washington, Baltimore, Maryland 21210, USA. cholm@ucsd.edu
Tuffo
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Koshland
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Holm
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D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002470:Cell Survival; D019457:Chromosome Breakage; D002875:Chromosomes / Q000502:physiology*; D004271:DNA, Fungal / Q000378:metabolism; D029721:Drosophila Proteins; D005434:Flow Cytometry; D017404:In Situ Hybridization, Fluorescence; D008938:Mitosis / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; D010957:Plasmids; D016196:S Phase / Q000235:genetics / Q000502:physiology; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000235:genetics / Q000378:metabolism*
C103227:Barr protein, Drosophila; D018797:Cell Cycle Proteins; D004271:DNA, Fungal; D029721:Drosophila Proteins; D009687:Nuclear Proteins