Contribution of H3K4 demethylase KDM5B to nucleosome organization in embryonic stem cells revealed by micrococcal nuclease sequencing

Positioning of nucleosomes along DNA is an integral regulator of chromatin accessibility and gene expression in diverse cell types. However, the precise nature of how post-translational modification of histones such as activating trimethylated histone 3 lysine 4 (H3K4me3), or histone demethylases including the H3K4 demethylase, KDM5B, impacts nucleosome positioning around transcriptional start sites (TSS) of active genes is poorly understood. Here, we report that KDM5B is a critical regulator of nucleosome positioning in embryonic stem (ES) cells. Micrococcal nuclease sequencing (MNase-Seq) revealed increased enrichment of nucleosomes around TSS regions and DNase I hypersensitive sites in KDM5B-depleted ES cells. Moreover, depletion of KDM5B resulted in a widespread redistribution and disorganization of nucleosomes in a sequence-dependent manner. Dysregulated nucleosome phasing was also evident in KDM5B-depleted ES cells, including asynchronous nucleosome spacing surrounding TSS regions, where nucleosome variance was positively correlated with the degree of asynchronous phasing. The redistribution of nucleosomes around TSS regions in KDM5B-depleted ES cells is correlated with dysregulated gene expression, and altered H3K4me3 and RNA polymerase II occupancy. In addition, we found that DNA shape features varied significantly at regions with shifted nucleosomes. Altogether, our data support a role for KDM5B in regulating nucleosome positioning in ES cells. MNase-Seq of murine shLuc and Kdm5b ES cells