Esco1 and Esco2 regulate distinct cohesin functions during cell cycle progression

Abstract

Sister chromatids are tethered together by the cohesin complex from the time they are made until their separation at anaphase. The ability of cohesin to tether sister chromatids together depends on acetylation of its Smc3 subunit by members of the Eco1 family of cohesin acetyltransferases. Vertebrates express two orthologs of Eco1, called Esco1 and Esco2, both of which are capable of modifying Smc3, but their relative contributions to sister chromatid cohesion are unknown. We therefore set out to determine the precise contributions of Esco1 and Esco2 to cohesion in vertebrate cells. Here we show that cohesion establishment is critically dependent upon Esco2. Although most Smc3 acetylation is Esco1 dependent, inactivation of the gene has little effect on mitotic cohesion. The unique ability of Esco2 to promote cohesion is mediated by sequences in the N terminus of the protein. We propose that Esco1-dependent modification of Smc3 regulates almost exclusively the noncohesive activities of cohesin, such as DNA repair, transcriptional control, chromosome loop formation, and/or stabilization. Collectively, our data indicate that Esco1 and Esco2 contribute to distinct and separable activities of cohesin in vertebrate cells.

Multivalent interaction of ESCO2 with the replication machinery is required for cohesion

“…3E). Because the cells lack functional ESCO1, all acetylation of SMC3 in these samples is ESCO2 dependent (Alomer et al, 2017). We found that in general the relative amount of SMC3 acetylation correlated with the amount of cohesion.…”

“…The functional difference between ESCO2 and the related ESCO1 maps to their distinct N termini, as opposed to their conserved C terminal acetyltransferase domains (Alomer et al, 2017). This suggests that the N terminus of ESCO2 might be sufficient to promote localization to replication foci.…”

“…Cells were transfected according to manufacturer's instructions using Lipofectamine 2000 (Invitrogen) for plasmid DNA or Lipofectamine RNAiMAX (Invitrogen) for siRNA. Stable cell lines with doxycycline-inducible siRNA-resistant Flag tagged ESCO2 cDNAs were generated using HeLa Flp-In T-Rex cells as previously (Alomer et al, 2017). The ESCO2 cDNA was cloned into a pcDNA5/FRTbased Flag-tag vector and co-transfected along with a plasmid expressing the FLP recombinase (pOG44, Invitrogen) using Lipofectamine 2000 (Invitrogen).…”

“…oil immersion lens. Phenotypes were assigned to mitotic chromosome spreads as previously (Alomer et al, 2017). Samples were scored blind and each experiment was repeated at least 3 times.…”

“…Although ESCO1 and ESCO2 have the same catalytic activity, they make distinct contributions to cohesin regulation. ESCO2 is uniquely able to promote cohesion between sister chromatids, though the majority of SMC3 acetylation is ESCO1 dependent (Song et al, 2012;Alomer et al, 2017).…”