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

TLDR

Sister chromatid cohesion is essential for chromosome segregation during mitosis, and its loss can trigger separation at the metaphase–anaphase transition by requiring degradation of anaphase inhibitors such as Pds1p to release the separase Esp1p. The study identified six proteins essential for sister chromatid cohesion: the Cohesin subunits Scc1p, Scc3p, Smc1p, and Smc3p, the non‑subunit Scc2p required for Cohesin loading, and Eco1p(Ctf7p), which is required for establishing cohesion during DNA replication but not for its maintenance in later phases.

Abstract

Sister chromatid cohesion is crucial for chromosome segregation during mitosis. Loss of cohesion very possibly triggers sister separation at the metaphase --> anaphase transition. This process depends on the destruction of anaphase inhibitory proteins like Pds1p (Cut2p), which is thought to liberate a sister-separating protein Esp1p (Cut1p). By looking for mutants that separate sister centromeres in the presence of Pds1p, this and a previous study have identified six proteins essential for establishing or maintaining sister chromatid cohesion. Four of these proteins, Scc1p, Scc3p, Smc1p, and Smc3p, are subunits of a 'Cohesin' complex that binds chromosomes from late G1 until the onset of anaphase. The fifth protein, Scc2p, is not a stoichiometric 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 not for its maintenance during G2 and M phases.