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The condensin complex is a key determinant of higher-ordered chromosome structure. We show here that the complex is also important for the correct alignment of chromosomes on the meiosis I spindle. Unlike during mitosis and meiosis II, when sister chromatids attach to microtubules emanating from opposite spindle poles (biorientation), accurate meiosis I chromosome segregation requires that sister chromatids attach to microtubules emanating from the same spindle pole (coorientation). The monopolin complex, consisting of Lrs4, Csm1, and the meiosis-specific component Mam1, brings about meiosis I coorientation. We find that in the absence of functional condensin complexes, a fraction of sister kinetochores biorient on the meiosis I spindle and association of the monopolin complex subunit Mam1 with kinetochores is decreased. Our studies uncover a new locus-specific effect of the condensin complex. [ABSTRACT FROM AUTHOR]

Sister-chromatid cohesion mediated by cohesin ensures proper chromosome segregation during cell division. Cohesin is also required for postreplicative DNA double-strand break repair and gene expression. The molecular mechanisms of these diverse cohesin functions remain to be elucidated. Here we report that the cohesin subunits Scc3 and Smc1 are both required for the production of the meiosis-specific subunit Rec8 in the budding yeast Saccharomyces cerevisiae. Using a genetic approach, we depleted Scc3 and Smc1 independently in cells that were undergoing meiosis. Both Scc3- and Smc1-depleted cells were inducible for meiosis, but the REC8 promoter was only marginally activated, leading to reduced levels of REC8 transcription and protein production. In contrast, the expression of MCD1, the mitotic counterpart of REC8, was not subject to Scc3 regulation in vegetative cells. We provide genetic evidence to show that sister-chromatid cohesion is not necessary for activation of REC8 gene expression. Cohesin appears to positively regulate the expression of a variety of genes during yeast meiosis. Our results suggest that the cohesin complex plays a dual role in gene regulation and sister-chromatid cohesion during meiotic differentiation in yeast. [ABSTRACT FROM AUTHOR]