SIRT6 and obesity due to melanocortin 4 receptor deficiency: Regarding the physiological role of H3K56 acetylation, recent work in Sirt6 knock-out mice reveals the association between hyperacetylation of H3K56 and obesity [16]: neural specific Sirt6-deleted mice have adult-onset obesity, and they show hyperacetylation at H3K9 and H3K56 in various brain regions [16].