Drosophila CP190- and dCTCF-mediated enhancer blocking is augmented by SUMOylation.

BACKGROUND: Chromatin insulators shield promoters and chromatin domains from neighboring enhancers or chromatin regions with opposing activities. Insulator-binding proteins and their cofactors mediate the boundary function. In general, covalent modification of proteins by the small ubiquitin-like modifier (SUMO) is an important mechanism to control the interaction of proteins within complexes.

RESULTS: Here we addressed the impact of dSUMO in respect of insulator function, chromatin binding of insulator factors and formation of insulator speckles in Drosophila . SUMOylation augments the enhancer blocking function of four different insulator sequences and increases the genome-wide binding of the insulator cofactor CP190.

CONCLUSIONS: These results indicate that enhanced chromatin binding of SUMOylated CP190 causes fusion of insulator speckles, which may allow for more efficient insulation.