Molecular Insights into the Recognition of Acetylated Histone Modifications by the BRPF2 Bromodomain

HBO1 (HAT bound to ORC), a member of the MYST family of histone acetyltransferases (HATs), was initially identified as a binding partner of the origin recognition complex (ORC) that acetylates free histone H3, H4, and nucleosomal H3. It functions as a quaternary complex with the BRPF (BRPF1/2/3) scaffolding protein and two accessory proteins, ING4/5 and Eaf6. BRPF2 interaction with HBO1 has been shown to be important for regulating H3K14 acetylation during embryonic development. However, how the BRPF2 directs the HBO1 HAT complex to chromatin to regulate its HAT activity towards nucleosomal substrates remains unclear. Our findings reveal novel interacting partners of the BRPF2 bromodomain that recognizes different acetyllysine residues on the N-terminus of histone H4, H3, and H2A and preferentially binds to H4K5ac, H4K8ac, and H4K5acK12ac modifications. Moreover, pull-down assays on the endogenous histones and mononucleosomes isolated from human cells confirmed that the BRPF2 bromodomain specifically showed a stronger affinity to H4K5ac marks. Further, mutational analysis of BRPF2 bromodomain coupled with ITC binding and pull-down assays on the histone substrates identified critical residues responsible for acetyllysine binding. Together, our study provides novel insights into how the histone binding function of the BRPF2 bromodomain directs the recruitment of the HBO1 HAT complex to chromatin to regulate gene expression. ![Figure][1] ### Competing Interest Statement The authors have declared no competing interest. * BRD : Bromodomain ITC : Isothermal titration calorimetry MD : Molecular dynamics BRPF1/2/3 : Bromodomain and PHD finger containing protein 1/2/3 PHD : Plant homeodomain ATAD2B : ATPase family AAA+ domain containing 2B PTM : Posttranslational modifications HBO1 : Histone acetyltransferase binding to ORC1 RMSD : Root-mean-square deviation TSA : Trichostatin A [1]: pending:yes