Histone H2A variants alpha1-extension helix directs RNF168-mediated ubiquitination

Jessica L Kelliher,Qingguo Gong,Kirk L West,Justin W C Leung

doi:10.1038/s41467-020-16307-4

Abstract

Histone ubiquitination plays an important role in the DNA damage response (DDR) pathway. RNF168 catalyzes H2A and H2AX ubiquitination on lysine 13/15 (K13/K15) upon DNA damage and promotes the accrual of downstream repair factors at damaged chromatin. Here, we report that RNF168 ubiquitinates the non-canonical H2A variants H2AZ and macroH2A1/2 at the divergent N-terminal tail lysine residue. In addition to their evolutionarily conserved nucleosome acidic patch, we identify the positively charged alpha1-extension helix as essential for RNF168-mediated ubiquitination of H2A variants. Moreover, mutation of the RNF168 UMI (UIM- and MIU-related UBD) hydrophilic acidic residues abolishes RNF168-mediated ubiquitination as well as 53BP1 and BRCA1 ionizing radiation-induced foci formation. Our results reveal a juxtaposed bipartite electrostatic interaction utilized by the nucleosome to direct RNF168 orientation towards the target lysine residues in proximity to the H2A alpha1-extension helix, which plays an important role in the DDR pathway.

Highlights

Histone ubiquitination plays an important role in the DNA damage response (DDR) pathway
RNF168 inactivation abolishes the recruitment of DNA repair proteins including BRCA1, RAD18, and RAP80 to DNA DSBs8,12, which highlights the important role of RNF168 as a mediator in the assembly of DNA
Histone ubiquitination is an integral part of the DDR pathway[1]

Summary

Introduction

Histone ubiquitination plays an important role in the DNA damage response (DDR) pathway. We report that RNF168 ubiquitinates the non-canonical H2A variants H2AZ and macroH2A1/ 2 at the divergent N-terminal tail lysine residue In addition to their evolutionarily conserved nucleosome acidic patch, we identify the positively charged alpha1-extension helix as essential for RNF168-mediated ubiquitination of H2A variants. In DSB repair, RNF168-mediated H2A and H2AX K15 ubiquitination recruits 53BP1 to damaged chromatin via direct protein-protein interaction. RNF168 inactivation abolishes the recruitment of DNA repair proteins including BRCA1, RAD18, and RAP80 to DNA DSBs8,12, which highlights the important role of RNF168 as a mediator in the assembly of DNA repair proteins at damaged chromatin. RNF168 has multiple ubiquitin-binding domains (UBD) including two MIU

Methods

Results

Conclusion