Histone H2B ubiquitination mediated chromatin relaxation is essential for the induction of somatic cell reprogramming

OBJECTIVES: Cell reprogramming has significant impacts on their potential application in regenerative medicine. Chromatin remodelling plays a very important role in cell reprogramming, but its underlying mechanism remains poorly understood. MATERIALS AND METHODS: RNA‐seq, quantitative RT‐PCR and western blot analysis were applied to study the role of RNF20 and H2B ubiquitination during mouse somatic cell reprogramming. Chromatin structure and the recruitment of transcription factors were analysed by ChIP‐seq, micrococcal nuclease sensitivity assays and immunofluorescence staining. RESULTS: We show that RNF20 is highly expressed at the early stage of reprogramming along with the accumulation of H2B ubiquitination at the same stage, and Rnf20 knockout results in the failure of reprogramming at the initial stage but not the maturation and stabilization stages. RNA‐seq showed that Rnf20 knockout mainly affects the early stage of cell reprogramming by impairing the transcription of MET‐related genes and early pluripotency genes. Importantly, Rnf20 knockout results in a more compacted chromosomes structure in reprogrammable cells, suppressing the recruitment of reprogramming transcription factors to their proper locations on the chromosomes, and finally resulting in the failure of pluripotent gene network establishment. CONCLUSIONS: Histone H2B ubiquitination mediated chromatin relaxation is essential for the induction of somatic cell reprogramming.