Hotspot Cancer Mutation Impairs KAT8-mediated Nucleosomal Histone Acetylation.

KAT8 is an evolutionarily conserved lysine acetyltransferase that catalyzes histone acetylation at H4K16 or H4K5 and H4K8 through distinct protein complexes. It plays a pivotal role in male X chromosome dosage compensation in Drosophila and is implicated in the regulation of diverse cellular processes in mammals. Mutations and dysregulation of KAT8 have been reported in human neurodevelopmental disorders and various cancers. However, the precise mechanisms by which these mutations disrupt KAT8's normal function, leading to disease pathogenesis, remain largely unknown. In this study, we focus on a hotspot missense cancer mutation, the R98W point mutation within the Tudor-knot domain. Our study reveals that the R98W mutation leads to a reduction in global H4K16ac levels in cells and downregulates the expression of target genes. Mechanistically, we demonstrate that R98 is essential for KAT8-mediated acetylation of nucleosomal histones by modulating substrate accessibility.