Multivalent histone and DNA engagement by a PHD/BRD/PWWP triple reader cassette recruits ZMYND8 to K14ac-rich chromatin

Elucidation of interactions involving DNA and histone post-translational-modifications (PTMs) is essential for providing insight into complex biological functions. Reader assemblies connected via flexible linkages facilitate avidity and increase affinity, however little is known of the contribution to the recognition process of multiple PTMs due to rigidity in the absence of conformational flexibility. We report here the high resolution crystal structure of the triple-reader module (PHD-Bromo-PWWP) of ZMYND8 which forms a stable unit capable of simultaneously recognizing multiple histone PTMs, while presenting a charged platform for association with DNA. Single domain disruptions destroy the functional network of interactions initiated by ZMYND8, impairing recruitment to sites of DNA damage. Our data establish proof-of-principle that rigidity can be compensated by concomitant DNA and histone PTM interactions, maintaining multivalent engagement of transient chromatin states, thus identifying an important underappreciated role for rigid multivalent reader modules in nucleosome binding and chromatin function.