The H2B ubiquitin-protein ligase RNF40 is required for somatic cell reprogramming

Wanhua Xie,Michaela Miehe,Steven A Johnsen,Sandra Laufer

doi:10.1038/s41419-020-2482-4

Abstract

Direct reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) requires a resetting of the epigenome in order to facilitate a cell fate transition. Previous studies have shown that epigenetic modifying enzymes play a central role in controlling induced pluripotency and the generation of iPSC. Here we show that RNF40, a histone H2B lysine 120 E3 ubiquitin-protein ligase, is specifically required for early reprogramming during induced pluripotency. Loss of RNF40-mediated H2B monoubiquitination (H2Bub1) impaired early gene activation in reprogramming. We further show that RNF40 contributes to tissue-specific gene suppression via indirect effects by controlling the expression of the polycomb repressive complex-2 histone methyltransferase component EZH2, as well as through more direct effects by promoting the resolution of H3K4me3/H3K27me3 bivalency on H2Bub1-occupied pluripotency genes. Thus, we identify RNF40 as a central epigenetic mediator of cell state transition with distinct functions in resetting somatic cell state to pluripotency.

Highlights

Somatic cells can be directly reprogrammed into a pluripotent state by forced expression of the Yamanaka factors Oct[4], Sox[2], Klf[4], and c-Myc[1]
Previous studies revealed that the H2B ubiquitin ligases RNF20 and RNF40 are essential for human mesenchymal stem cell and mouse embryonic stem cell differentiation by controlling cell lineage-specific gene expression[10,11,13]
The efficiency of induced pluripotent stem cells (iPSCs) generation was analyzed at day 20 by counting the alkaline phosphatase-positive (AP+) colonies (Fig. 1a)[42]

Summary

Introduction

Somatic cells can be directly reprogrammed into a pluripotent state by forced expression of the Yamanaka factors Oct[4], Sox[2], Klf[4], and c-Myc[1]. Even though these factors can be stably activated in somatic cells, the generation of high-quality induced pluripotent stem cells (iPSCs) is highly inefficient, with low frequency and a long latency[2,3]. Epigenetic modifications, including DNA methylation and post-translational histone modifications, have been demonstrated to activate or repress particular important subsets of genes during cell fate transition.

Methods

Results

Conclusion