Abstract: The establishment of stable sister chromatid cohesion during DNA replication requires acetylation of the chromosomal cohesin complex by the replication fork-associated acetyltransferase Eco1 [1Tóth A. Ciosk R. Uhlmann F. Galova M. Schleiffer A. Nasmyth K. Yeast cohesin complex requires a conserved protein, Eco1p(Ctf7), to establish cohesion between sister chromatids during DNA replication.Genes Dev. 1999; 13: 320-333Crossref PubMed Scopus (499) Google Scholar, 2Skibbens R.V. Corson L.B. Koshland D. Hieter P. Ctf7p is essential for sister chromatid cohesion and links mitotic chromosome structure to the DNA replication machinery.Genes Dev. 1999; 13: 307-319Crossref PubMed Scopus (384) Google Scholar, 3Ivanov D. Schleiffer A. Eisenhaber F. Mechtler K. Haering C.H. Nasmyth K. Eco1 is a novel acetyltransferase that can acetylate proteins involved in cohesion.Curr. Biol. 2002; 12: 323-328Abstract Full Text Full Text PDF PubMed Scopus (202) Google Scholar, 4Lengronne A. McIntyre J. Katou Y. Kanoh Y. Hopfner K.-P. Shirahige K. Uhlmann F. Establishment of sister chromatid cohesion at the S. cerevisiae replication fork.Mol. Cell. 2006; 23: 787-799Abstract Full Text Full Text PDF PubMed Scopus (227) Google Scholar, 5Moldovan G.-L. Pfander B. Jentsch S. PCNA controls establishment of sister chromatid cohesion during S phase.Mol. Cell. 2006; 23: 723-732Abstract Full Text Full Text PDF PubMed Scopus (212) Google Scholar, 6Rolef Ben-Shahar T. Heeger S. Lehane C. East P. Flynn H. Skehel M. Uhlmann F. Eco1-dependent cohesin acetylation during establishment of sister chromatid cohesion.Science. 2008; 321: 563-566Crossref PubMed Scopus (365) Google Scholar, 7Ünal E. Heidinger-Pauli J.M. Kim W. Guacci V. Onn I. Gygi S.P. Koshland D.E. A molecular determinant for the establishment of sister chromatid cohesion.Science. 2008; 321: 566-569Crossref PubMed Scopus (329) Google Scholar, 8Zhang J. Shi X. Li Y. Kim B.-J. Jia J. Huang Z. Yang T. Fu X. Jung S.Y. Wang Y. et al.Acetylation of Smc3 by Eco1 is required for S phase sister chromatid cohesion in both human and yeast.Mol. Cell. 2008; 31: 143-151Abstract Full Text Full Text PDF PubMed Scopus (306) Google Scholar]. Cohesin acetylation is thought to facilitate replication fork progression by counteracting an as yet ill-defined cohesion “antiestablishment” activity imposed by the Wapl protein [9Rowland B.D. Roig M.B. Nishino T. Kurze A. Uluocak P. Mishra A. Beckouët F. Underwood P. Metson J. Imre R. et al.Building sister chromatid cohesion: smc3 acetylation counteracts an antiestablishment activity.Mol. Cell. 2009; 33: 763-774Abstract Full Text Full Text PDF PubMed Scopus (233) Google Scholar, 10Terret M.-E. Sherwood R. Rahman S. Qin J. Jallepalli P.V. Cohesin acetylation speeds the replication fork.Nature. 2009; 462: 231-234Crossref PubMed Scopus (177) Google Scholar, 11Sutani T. Kawaguchi T. Kanno R. Itoh T. Shirahige K. Budding yeast Wpl1(Rad61)-Pds5 complex counteracts sister chromatid cohesion-establishing reaction.Curr. Biol. 2009; 19: 492-497Abstract Full Text Full Text PDF PubMed Scopus (167) Google Scholar]. Here, using budding yeast, we find no evidence that cohesin acetylation must overcome Wapl during replication fork progression. Instead, Wapl emerges as a negative regulator of cohesion maintenance in G2, a function that it likely exerts through its role as destabilizer of unacetylated, chromosome-bound cohesin. Our results suggest that acetylation renders cohesin Wapl-resistant from S phase onward until mitosis. In the absence of Wapl, sister chromatid cohesion functions well [6Rolef Ben-Shahar T. Heeger S. Lehane C. East P. Flynn H. Skehel M. Uhlmann F. Eco1-dependent cohesin acetylation during establishment of sister chromatid cohesion.Science. 2008; 321: 563-566Crossref PubMed Scopus (365) Google Scholar], suggesting that Wapl partakes in a cohesin function outside of sister chromatid cohesion. We find that Wapl is not required for cohesin’s known role in transcriptional regulation. Rather, cells lacking Wapl display increased chromosome condensation in both interphase and mitosis. Thus, as a conserved regulator of cohesin dynamics on chromosomes, Wapl controls cohesion maintenance after its establishment in S phase and adjusts the chromosome condensation status.