Yeast Cohesin complex requires a conserved protein, Eco1p(Ctf7), to establish cohesion between sister chromatids during DNA replication

Sister chromatid cohesion is crucial for chromosome segregation during mito sis. Loss of cohesion very possibly triggers sister separation at the metap hase --> anaphase transition. This process depends on the destruction of an aphase inhibitory proteins like Pds1p (Cut2p), which is thought to liberate a sister-separating protein Esp1p (Cut1p). By looking for mutants that sep arate sister centromeres in the presence of Pds1p, this and a previous stud y have identified six proteins essential for establishing or maintaining si ster chromatid cohesion. Four of these proteins, Scc1p, Scc3p, Smc1p, and S mc3p, are subunits of a 'Cohesin' complex that binds chromosomes from late G(1) until the onset of anaphase. The fifth protein, Scc2p, is not a stoich iometric Cohesin subunit but it is required for Cohesin's association with chromosomes. The sixth protein, Eco1p(Ctf7p), is not a Cohesin subunit. It is necessary for the establishment of cohesion during DNA replication but n ot for its maintenance during G(2) and M phases.