Acetylation of SMC3 subunit of centromeric chromatin associated cohesin by ESCO1 or ESCO2 Acetyltransferases ESCO1 and ESCO2 are homologs of the S. cerevisiae acetyltransferase Eco1, essential for viability in yeast. ESCO1 and ESCO2 share sequence homology in the C-terminal region, consisting of a H2C2 zinc finger motif and an acetyltransferase domain (Hou and Zou 2005). Both ESCO1 and ESCO2 acetylate the cohesin subunit SMC3 on two lysine residues, K105 and K106 (Zhang et al. 2008), an important step in the establishment of sister-chromatid cohesion during the S-phase of the cell cycle. Divergent N-termini of ESCO1 and ESCO2, necessary for chromatin binding, suggest that ESCO1 and ESCO2 may perform distinct functions in sister chromatid cohesion (Hou and Zou 2005). Several studies suggest that ESCO2 may be predominantly involved in acetylation of the SMC3 subunit of centromeric cohesin. A conditional targeting of Esco2 locus in mice leads to pre-implantational loss of homozygous Esco2 -/- embryos at the eight-cell stage. Prometaphase chromosomes isolated from two-cell stage Esco2 knockout embryos show marked cohesion defect at centromeres (Whelan et al. 2012). ESCO2 protein appears in the S-phase (Hou and Zou 2005, Whelan et al. 2012) and in mouse embryonic fibroblasts Esco2 predominantly localizes to pericentric heterochromatin (Whelan et al. 2012). Mutations in the ESCO2 gene (Vega et al. 2005) that impair ESCO2 acetyltransferase activity (Gordillo et al. 2008) are the cause of the Roberts syndrome, an autosomal recessive disorder characterized by craniofacial and limb abnormalities, and intellectual disability. Metaphase chromosomes of Roberts syndrome patients exhibit loss of cohesion at heterochromatic regions of centromeres and the Y chromosome, with a characteristic 'railroad track appearance' (Van den Berg and Francke 1993, Vega et al. 2005). Authored: Orlic-Milacic, M, 2012-10-02 Edited: Gillespie, ME, 2012-10-05 Edited: Matthews, L, 2012-10-05 Pubmed15821733 Pubmed15958495 Pubmed18411254 Pubmed18614053 Pubmed21111234 Pubmed22101327 Pubmed8291532 Reactome Database ID Release 432473152 Reactome, http://www.reactome.org ReactomeREACT_150144 Reviewed: Zhang, Nenggang, 2012-10-22 has a Stoichiometric coefficient of 2 Ac-Cohesin:PDS5:WAPAL:Centromere Cohesin:PDS5:WAPAL:Centromere