Nut is a cell type-specific stimulator of p300 enhancing H4 hyperacetylation during haploid male genome programming. 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. Overall design: MNase-Seq in round-elongating spermatids from WT and Nut-KO mice

睾丸核蛋白（nuclear protein in testis，以下简称NUT）是高侵袭性NUT中线癌（NMC）中BRD4的通用融合伴侣，但其生理功能迄今尚未明确。本研究发现，NUT特异性表达于减数分裂后生精细胞，且表达时点与全基因组组蛋白高度乙酰化阶段重合。NUT失活可诱导精子发生阻滞于组蛋白向鱼精蛋白替换阶段，最终导致雄性不育。后续分子实验显示，NUT能够维持减数分裂后生精细胞的全局组蛋白H4高度乙酰化水平。此外，NUT介导依赖于p300/CBP的基因表达程序，并通过增强H4蛋白K5与K8位点的乙酰化修饰，为Brdt的首个溴结构域提供结合位点，进而推动组蛋白移除。本研究首次揭示了NUT在生精细胞中的功能：NUT借助广泛分布的组蛋白乙酰转移酶（histone acetyltransferases，简称HATs）p300/CBP，调控细胞类型特异性的组蛋白H4高度乙酰化。NUT在NMC中的异位表达活性，重现了正常生理状态下于减数分裂后生精细胞中运作的、由p300诱导的组蛋白高度乙酰化/溴结构域结合环路。实验整体设计：对野生型（wild type，简称WT）与NUT基因敲除（Nut-KO）小鼠的圆形-延长型精子细胞开展微球菌核酸酶测序（MNase-Seq）。