Dynamic Competing Histone H4 K5K8 Acetylation and Butyrylation Are Hallmarks of Highly Active Gene Promoters

Recently discovered histone lysine acylation marks increase the functional diversity of nucleosomes well beyond acetylation. Here, we focus on histone butyrylation in the context of sperm cell differentiation. Specifically, we investigate the butyrylation of histone H4 lysine 5 and 8 at gene promoters where acetylation guides the binding of Brdt, a bromodomain-containing protein, thereby mediating stage-specific gene expression programs and post-meiotic chromatin reorganization. Genome-wide mapping data show that highly active Brdt-bound gene promoters systematically harbor competing histone acetylation and butyrylation marks at H4 K5 and H4 K8. Despite acting as a direct stimulator of transcription, histone butyrylation competes with acetylation, especially at H4 K5, to prevent Brdt binding. Additionally, H4 K5K8 butyrylation also marks retarded histone removal during late spermatogenesis. Hence, alternating H4 acetylation and butyrylation, while sustaining direct gene activation and dynamic bromodomain binding, could impact the final male epigenome features. [Display omitted] •Active gene TSSs are marked by competing H4 K5K8 acetylation and butyrylation•Histone butyrylation directly stimulates transcription•H4K5 butyrylation prevents binding of the testis specific gene expression-driver Brdt•H4K5K8 butyrylation is associated with delayed histone removal in spermatogenic cells Histone butyrylation stimulates gene transcription while competing with acetylation at H4K5 to control Brdt bromodomain binding. Differential chromatin labeling with interchangeable H4 acylations is an important epigenetic regulatory mechanism controlling gene expression and chromatin reorganization.