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EMBO J. 2017 Apr 13;36(8):1066-1083. doi: 10.15252/embj.201695151. Epub 2017 Mar 8.

Ataxin-3 consolidates the MDC1-dependent DNA double-strand break response by counteracting the SUMO-targeted ubiquitin ligase RNF4.

Author information

1
Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden.
2
Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands.
3
Department of Human Genetics, Leiden University Medical Center, Leiden, The Netherlands h.van.attikum@lumc.nl nico.dantuma@ki.se.
4
Department of Cell and Molecular Biology, Karolinska Institutet, Stockholm, Sweden h.van.attikum@lumc.nl nico.dantuma@ki.se.

Abstract

The SUMO-targeted ubiquitin ligase RNF4 functions at the crossroads of the SUMO and ubiquitin systems. Here, we report that the deubiquitylation enzyme (DUB) ataxin-3 counteracts RNF4 activity during the DNA double-strand break (DSB) response. We find that ataxin-3 negatively regulates ubiquitylation of the checkpoint mediator MDC1, a known RNF4 substrate. Loss of ataxin-3 markedly decreases the chromatin dwell time of MDC1 at DSBs, which can be fully reversed by co-depletion of RNF4. Ataxin-3 is recruited to DSBs in a SUMOylation-dependent fashion, and in vitro it directly interacts with and is stimulated by recombinant SUMO, defining a SUMO-dependent mechanism for DUB activity toward MDC1. Loss of ataxin-3 results in reduced DNA damage-induced ubiquitylation due to impaired MDC1-dependent recruitment of the ubiquitin ligases RNF8 and RNF168, and reduced recruitment of 53BP1 and BRCA1. Finally, ataxin-3 is required for efficient MDC1-dependent DSB repair by non-homologous end-joining and homologous recombination. Consequently, loss of ataxin-3 sensitizes cells to ionizing radiation and poly(ADP-ribose) polymerase inhibitor. We propose that the opposing activities of RNF4 and ataxin-3 consolidate robust MDC1-dependent signaling and repair of DSBs.

KEYWORDS:

SUMO ; DNA damage response; DNA repair; deubiquitylation enzyme; ubiquitin

PMID:
28275011
PMCID:
PMC5391139
DOI:
10.15252/embj.201695151
[Indexed for MEDLINE]
Free PMC Article

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