Cohesin acetylation by Eco1 during DNA replication establishes sister chromatid cohesion. We show that acetylation makes cohesin resistant to Wapl activity from S-phase until mitosis. Wapl turns out to be a key regulator of cohesin dynamics on chromosomes by controling cohesin maintenance following its establishment in S-phase and its role in chromosome condensation. Overall design: The Affymetrix Yeast Genome 2.0 Arrays were used to analyze the expression profile of wt and wapl∆ cells.