H2A.Z.1 Monoubiquitylation Antagonizes BRD2 to Maintain Poised Chromatin in ESCs.

Lauren E Surface,Sally E Peach,Jacob D Jaffe,Russell Behmer,Laurie A Boyer,Namrata Udeshi,Steven A Carr,Vidya Subramanian,Paul A Fields

doi:10.1016/j.celrep.2015.12.100

Lauren E Surface, Sally E Peach + Show 7 more

Open Access

https://doi.org/10.1016/j.celrep.2015.12.100

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Abstract

Histone variant H2A.Z occupies the promoters of active and poised, bivalent genes in embryonic stem cells (ESCs) to regulate developmental programs, yet how it contributes to these contrasting states is poorly understood. Here, we investigate the function of H2A.Z.1 monoubiquitylation (H2A.Z.1ub) by mutation of the PRC1 target residues (H2A.Z.1(K3R3)). We show that H2A.Z.1(K3R3) is properly incorporated at target promoters in murine ESCs (mESCs), but loss of monoubiquitylation leads to de-repression of bivalent genes, loss of Polycomb binding, and faulty lineage commitment. Using quantitative proteomics, we find that tandem bromodomain proteins, including the BET family member BRD2, are enriched in H2A.Z.1 chromatin. We further show that BRD2 is gained at de-repressed promoters in H2A.Z.1(K3R3) mESCs, whereas BRD2 inhibition restores gene silencing at these sites. Together, our study reveals an antagonistic relationship between H2A.Z.1ub and BRD2 to regulate the transcriptional balance at bivalent genes to enable proper execution of developmental programs.

Highlights

Pluripotent cells must translate signaling cues into rapid transcriptional responses during development to specify the many cell types in the adult
Using a transgenic murine ESCs (mESCs) system, we show that H2A.Z.1ub is necessary for both proper induction of developmental programs and the maintenance of bivalent chromatin, including PRC2 recruitment
We found that H2A.Z.1WT and H2A.Z.1K3R3 are enriched in chromatin by fractionation of mESCs lysates (Figure S2H)

Summary

Graphical Abstract

Shedding light on the contrasting functions of the histone variant H2A.Z.1 in gene regulation, Surface et al show that H2A.Z.1 monoubiquitylation is required for the transcriptional repression of developmental promoters in mESCs by antagonizing downstream transcriptional activators including the BET bromodomain family member BRD2. Highlights d Polycomb-mediated H2A.Z.1ub is required for repression of bivalent genes in mESCs. GSE53208 GSE67944 d Loss of H2A.Z.1ub leads to faulty lineage commitment of mESCs d H2A.Z.1ub promotes the association of PRC2 and H3K27me with bivalent promoters d H2A.Z.1ub antagonizes binding of the BET bromodomain transcriptional activator BRD2.

SUMMARY

INTRODUCTION

RESULTS

H2A-YFP

DISCUSSION

EXPERIMENTAL PROCEDURES