Dynamic competing histone H4 K5K8 acetylation and butyrylation are hallmarks of highly active gene promoters. Mus musculus

Newly discovered histone lysine acylations 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-and-extra-terminal protein, thereby mediating stage-specific gene expression programs. Genome-wide mapping data show that highly active Brdt-bound gene promoters systematically harbour competing histone acetylation and butyrylation marks at H4 K5 and K8. Histone butyrylation, despite acting as a direct stimulator of transcription, competes with acetylation, especially at H4 K5, to prevent Brdt binding. The observed in vivo H4 K5K8 acetylation butyrylation state at active promoters is reproduced in vitro where p300 indistinctly acetylates and butyrylates H4 K5 and K8. Altogether, highly active gene promoter regions are characterized by alternating H4 acetylation and butyrylation sustaining direct gene activation and a dynamic bromodomain binding. Overall design: Examination of 4 different histone modifications, butyrylation of H4K5 and of H4K8, and acetylation of H4K5 and H4K8, in mouse spermatogenic cells at 2 stages: spermatocytes and round spermatids.