Re-evaluating the localization of sperm-retained histones using nucleoplasmin. Mus

The question of whether retained histones in the sperm genome localize to gene coding regions or gene deserts has been debated for years. Previous contradictory observations are likely caused by the non-uniform sensitivity of sperm chromatin to micrococcal nuclease (MNase) digestion. Sperm chromatin has a highly condensed but heterogeneous structure, and in mouse is composed of ~99% protamines and ~1% histones. In this study, we utilized nucleoplasmin (NPM) to improve the solubility of sperm chromatin by removing protamines in vitro. NPM treatment efficiently solubilized histones while maintaining quality and quantity. ChIP-seq analyses using NPM-treated sperm were performed to re-evaluate the localization of sperm-retained histones.