“…Xenopus Groucho is SUMOylated at multiple sites, and SUMOylation enhances its corepressor activity (Ahn et al, 2009). Similarly, the yeast Groucho ortholog Tup1 has recently been shown to be SUMOylated, and although mutation of its SUMO sites does not affect initial recruitment to target promoters, it does affect its ability to remain on the promoters, suggesting SUMO stabilizes the corepressor complex (Ng et al, 2015). Interestingly, Tup1 interaction partners histone H3, Cti6, Gcn5, Gal11, and Cyc8 also become SUMOylated under similar conditions as Tup1, and SUMO may generally hold together transcriptional repressor complexes in the same manner that SUMO protein functions to hold together DNA repair systems and PML nuclear bodies (Psakhye and Jentsch, 2012; Shen et al, 2006).…”