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.