Required for establishment of sister chromatid cohesion during S phase but not for its further maintenance during G2 or M phases or for loading the cohesin complex onto DNA. Interacts with the three known alternate replication factor C (RFC) complexes, suggesting that these complexes have essential but redundant activity in cohesion establishment. Acts by acetylating the cohesin complex component SMC3. In vitro, possesses acetyltransferase activity where it can acetylate itself and components of the cohesin complex (MCD1, IRR1 and PDS5), but is unable to acetylate histones. Binds specifically to CHL12, RFC1, RFC2, RFC3, RFC4, RFC5 and RAD24 when members of an RFC complex. Interacts with CHL1 and MPS3. Associated with chromatin. Autoacetylates in vitro. Belongs to the acetyltransferase family. ECO subfamily.