a, Multiple sequence alignment of SA2 (here denoted STAG2) orthologues and paralogues. *Key amino-acid residues that engage CTCF. b, Missense mutation frequencies plotted onto the SA2 structure. R370 (a hotspot in SA2) is indicated. The inset shows an overview of the mutation hotspots R370 of SA2), Y226 and F228 of CTCF, and S334, K335, R338 and L341 of SCC). c, ITC progress curves of binding between WAPL(423–463) and SA2–SCC1. d, Competition between SGO1 and CTCF for SA2–SCC1 binding. SA2–SCC1 was incubated with GST–CTCF(86–267). Increasing amounts (lanes 4–8) (molar ratios are indicated) of the SGO1 phosphorylated at T346 peptide (spanning residues 331–349) were added and the input and the bound fraction analysed by SDS–PAGE. The experiment was repeated twice. One representative example is shown. e, Domain architecture and sequence alignments of cohesin regulators that contain F/YXF motifs. Putative CES-interacting residues are highlighted in red. f, Regular expression motif used to query the human and yeast proteomes for factors containing F/YXF motifs. Regular expression syntax: letters denote a specific amino acid; square brackets denote a subset of allowed amino acids; curly brackets denote length variability.