Irr1/Scc3 cohesin interacts with Rec8 in meiotic prophase of Saccharomyces cerevisiae

The meiotic cohesin complex of S. cerevisiae shares with the mitotic one the Irr1/Scc3, Smc1, and Smc3 subunits, while the meiosis-specific subunit Rec8 replaces mitotic subunit Scc1/Mcd1. We noticed earlier that the irr1-1 mutation (F658G) severely affected meiosis. The irr1-1/IRR1 cells were entering meiosis before having completed mitotic cell division. Using meiotic two-hybrid assay and co-immunoprecipitation we show that in cells arrested in pachytene due to a lack of a gene-regulatory factor Ndt80, the Irr1 protein interacts with Rec8p and the irr1-1 mutation abolishes this interaction. These findings indicate an important role of Irr1p in early stages of meiosis.