Molecular Basis for Cohesin Acetylation by Establishment of Sister Chromatid Cohesion N-Acetyltransferase ESCO1

Abstract

Protein acetylation is a prevalent posttranslational modification that is regulated by diverse acetyltransferase enzymes. Although histone acetyltransferases (HATs) have been well characterized both structurally and mechanistically, far less is known about non-histone acetyltransferase enzymes. The human ESCO1 and ESCO2 paralogs acetylate the cohesin complex subunit SMC3 to regulate the separation of sister chromatids during mitosis and meiosis. Missense mutations within the acetyltransferase domain of these proteins correlate with diseases, including endometrial cancers and Roberts syndrome. Despite their biological importance, the mechanisms underlying acetylation by the ESCO proteins are not understood. Here, we report the X-ray crystal structure of the highly conserved zinc finger-acetyltransferase moiety of ESCO1 with accompanying structure-based mutagenesis and biochemical characterization. We find that the ESCO1 acetyltransferase core is structurally homologous to the Gcn5 HAT, but contains unique additional features including a zinc finger and an ∼40-residue loop region that appear to play roles in protein stability and SMC3 substrate binding. We identify key residues that play roles in substrate binding and catalysis, and rationalize the functional consequences of disease-associated mutations. Together, these studies reveal the molecular basis for SMC3 acetylation by ESCO1 and have broader implications for understanding the structure/function of non-histone acetyltransferases.

Alternative catalytic residues in the active site of Esco acetyltransferases

“…3E, 3F, 3G, and 3H). Rivera-Colon et al 38 reported that wild-type protein and the four mutants used here show similar thermal stability, arguing against the possibility that mutant HsESCO1 proteins were unfolded and hence became catalytically inactive. Together, these results indicate that D810 and the neighboring S809 are required for catalytic activity of the HsESCO1 enzyme, when using reconstituted recombinant cohesin substrates.…”

“…However, in a more recent study 38 , this role was attributed to an aspartate (D810) from the active site of HsESCO1. Mutation of this highly conserved aspartate to an asparagine inactivated the enzyme, according to an enzymatic assay that made use of Smc3 peptide as a substrate.…”

“…In contrast, Rivera-Colon et al proposed that D810 of HsESCO1 plays the role of a general base. Indeed, mutating this aspartate to asparagine abrogates acetylation of an Smc3 peptide mimicking SMC substrate 38 . A subsequent study by Chao et al has observed that in the Xenopus xEco2/Smc3 peptide structure, the Smc3 D107 does not point towards the ϵ-amino group of the substrate lysines but interacts with two conserved R621 and W623 residues of xEco2.…”

Chemical Biology Approaches for Investigating the Functions of Lysine Acetyltransferases

“…[36] Structural studies found that the ESCO1 acetyltransferase core is structurally homologous to the GCN5 KAT. [37] Cohen et al showed that the microtubule-associated protein tau (MAPT) possesses intrinsic enzymatic activity for catalyzing self-acetylation. [38] It remains unknown whether MAPT acetylates cytoplasmic or microtubule-associated proteins.…”

Untersuchung der epigenetischen Funktionen von Lysin‐Acetyltransferasen mit Methoden der chemischen Biologie

“…[36] Strukturuntersuchungen ergaben, dass der ESCO1-Acetyltransferasekern zur GCN5-KATs trukturell homolog ist. [37] Cohen et al beobachteten fürdas Mikrotubuli-assoziierte Protein Tau(MAPT) eine intrinsische Enzymaktivitätz ur Katalyse von Selbstacetylierung. [38] Es ist jedoch weiter unbekannt, ob MAPT zytoplasmatische oder Mikrotubuli-assoziierte Proteine acetyliert.…”