Chromosome condensation factor Brn1p is required for chromatid separation in mitosis.
This work describes BRN1, the budding yeast homologue of Drosophila Barren and Xenopus condensin subunit XCAP-H. The Drosophila protein is required for proper chromosome segregation in mitosis, and Xenopus protein functions in mitotic chromosome condensation. Mutant brn1 cells show a defect in mitotic chromosome condensation and sister chromatid separation and segregation in anaphase. Chromatid cohesion before anaphase is properly maintained in the mutants. Some brn1 mutant cells apparently arrest in S-phase, pointing to a possible function for Brn1p at this stage of the cell cycle. Brn1p is a nuclear protein with a nonuniform distribution pattern, and its level is up-regulated at mitosis. Temperature-sensitive mutations of BRN1 can be suppressed by overexpression of a novel gene YCG1, which is homologous to another Xenopus condensin subunit, XCAP-G. Overexpression of SMC2, a gene necessary for chromosome condensation, and a homologue of the XCAP-E condensin, does not suppress brn1, pointing to functional specialization of components of the condensin complex.
Ouspenski
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Department of Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA.
Cabello
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OA
Brinkley
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BR
D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism*; D002842:Chromatids / Q000502:physiology; D002875:Chromosomes / Q000502:physiology*; D004271:DNA, Fungal / Q000032:analysis; D029721:Drosophila Proteins; D017404:In Situ Hybridization, Fluorescence; D008938:Mitosis / Q000235:genetics / Q000502:physiology*; D009154:Mutation; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism*; 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