Structural Insight into Binding of the ZZ Domain of HERC2 to Histone H3 and SUMO1.

Human ubiquitin ligase HERC2, a component of the DNA repair machinery, has been linked to neurological diseases and cancer. Here, we show that the ZZ domain of HERC2 (HERC2ZZ) binds to histone H3 tail and tolerates posttranslational modifications commonly present in H3. The crystal structure of the HERC2ZZ:H3 complex provides the molecular basis for this interaction and highlights a critical role of the negatively charged site of HERC2ZZ in capturing of A1 of H3. NMR, mutagenesis, and fluorescence data reveal that HERC2ZZ binds to H3 and the N-terminal tail of SUMO1, a previously reported ligand of HERC2ZZ, with comparable affinities. Like H3, the N-terminal tail of SUMO1 occupies the same negatively charged site of HERC2ZZ in the crystal structure of the complex, although in contrast to H3 it adopts an α-helical conformation. Our data suggest that HERC2ZZ may play a role in mediating the association of HERC2 with chromatin.