Evidence that ubiquitylated H2B corrals hDot1L on the nucleosomal surface to induce H3K79 methylation.

Linjiao Zhou,Boyuan Wang,Manuel M Müller,Tom W Muir,Matthew T Holt,Aishan Zhao,Nami Ohashi

doi:10.1038/ncomms10589

Linjiao Zhou, Boyuan Wang + Show 5 more

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https://doi.org/10.1038/ncomms10589

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Abstract

Ubiquitylation of histone H2B at lysine 120 (H2B-Ub), a post-translational modification first discovered in 1980, plays a critical role in diverse nuclear processes including the regulation of transcription and DNA damage repair. Herein, we use a suite of protein chemistry methods to explore how H2B-Ub stimulates hDot1L-mediated methylation of histone H3 on lysine 79 (H3K79me). By using semisynthetic ‘designer' chromatin containing H2B-Ub bearing a site-specifically installed photocrosslinker, here we report an interaction between a functional hotspot on ubiquitin and the N-terminus of histone H2A. Our biochemical studies indicate that this interaction is required for stimulation of hDot1L activity and leads to a repositioning of hDot1L on the nucleosomal surface, which likely places the active site of the enzyme proximal to H3K79. Collectively, our data converge on a possible mechanism for hDot1L stimulation in which H2B-Ub physically ‘corrals' the enzyme into a productive binding orientation.

Highlights

Ubiquitylation of histone H2B at lysine 120 (H2B-Ub), a post-translational modification first discovered in 1980, plays a critical role in diverse nuclear processes including the regulation of transcription and DNA damage repair
The H3K79me/H2B-Ub crosstalk operates in an intranucleosomal fashion and requires a specific surface epitope on ubiquitin since other ubiquitin-like proteins with a similar size and structure to ubiquitin do not stimulate hDot1L activity when conjugated to H2B at the same site, that is, lysine 120
As a starting point for our studies, we focused on the recent identification of a discrete surface epitope on ubiquitin, centred on Leu71/Leu[73], required for hDot1L activation[18]

Summary

Introduction

Ubiquitylation of histone H2B at lysine 120 (H2B-Ub), a post-translational modification first discovered in 1980, plays a critical role in diverse nuclear processes including the regulation of transcription and DNA damage repair. An emerging paradigm in epigenetic regulation is the functional crosstalk between histone post-translational modifications (PTMs), that is, where the presence of a pre-existing PTM on the chromatin template can positively or negatively regulate the local installation or removal of another PTM1. This interplay can operate in cis, where the crosstalk pair is located on the same histone protein, or in trans where the pair is located on different histones either within the same nucleosome or, in principle, spatially adjacent nucleosomes[1]. Our in vitro studies are consistent with a ‘corralling’ type mechanism in which ubiquitin is positioned on the nucleosomal surface so as to occlude non-productive hDot1L binding orientations

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