Nut is a cell type-specific stimulator of p300 enhancing H4 hyperacetylation during haploid male genome programming

NUT, nuclear protein in testis is the universal fusion partner of BRD4 in the highly aggressive NUT Midline Carcinoma (NMC), but its physiological function is unknown. Here we show that Nut is exclusively expressed in post-meiotic spermatogenic cells, at the time of genome-wide histone hyperacetylation. Inactivation of Nut induces a spermatogenesis arrest at the histone-to-protamine replacement stage, leading to male infertility. Subsequent molecular investigations show that Nut sustains global histone H4 hyperacetylation in post-meiotic cells. Additionally, Nut mediates a p300/CBP-dependent gene expression program and, by enhancing acetylation of H4 at both K5 and K8 sites, provides binding sites for the first bromodomain of Brdt, which drives histone removal. Our results bring the first evidence of Nut’s function in spermatogenic cells where it uses the ubiquitous HATs p300/CBP to direct a cell-type specific histone H4 hyperacetylation. The ectopic activity of Nut in NMC recreates a forced p300-induced histone hyperacetylation / bromodomain-binding loop that normally operates in post-meiotic spermatogenic cells. MNase-Seq in round-elongating spermatids from WT and Nut-KO mice