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Nucleic Acids Res. 2016 Feb 18;44(3):1161-78. doi: 10.1093/nar/gkv1196. Epub 2015 Nov 17.

DNA-PK triggers histone ubiquitination and signaling in response to DNA double-strand breaks produced during the repair of transcription-blocking topoisomerase I lesions.

Author information

1
Cancer Research Center of Toulouse, INSERM UMR1037, Toulouse 31037, France.
2
Department of Pharmacy and Biotechnology, University of Bologna, Bologna 40126, Italy.
3
Université de Toulouse, UPS, LBCMCP, 31062 Toulouse, France CNRS, LBCMCP, 31062 Toulouse, France.
4
Cancer Research Center of Toulouse, INSERM UMR1037, Toulouse 31037, France olivier.sordet@inserm.fr.

Abstract

Although defective repair of DNA double-strand breaks (DSBs) leads to neurodegenerative diseases, the processes underlying their production and signaling in non-replicating cells are largely unknown. Stabilized topoisomerase I cleavage complexes (Top1cc) by natural compounds or common DNA alterations are transcription-blocking lesions whose repair depends primarily on Top1 proteolysis and excision by tyrosyl-DNA phosphodiesterase-1 (TDP1). We previously reported that stabilized Top1cc produce transcription-dependent DSBs that activate ATM in neurons. Here, we use camptothecin (CPT)-treated serum-starved quiescent cells to induce transcription-blocking Top1cc and show that those DSBs are generated during Top1cc repair from Top1 peptide-linked DNA single-strand breaks generated after Top1 proteolysis and before excision by TDP1. Following DSB induction, ATM activates DNA-PK whose inhibition suppresses H2AX and H2A ubiquitination and the later assembly of activated ATM into nuclear foci. Inhibition of DNA-PK also reduces Top1 ubiquitination and proteolysis as well as resumption of RNA synthesis suggesting that DSB signaling further enhances Top1cc repair. Finally, we show that co-transcriptional DSBs kill quiescent cells. Together, these new findings reveal that DSB production and signaling by transcription-blocking Top1 lesions impact on non-replicating cell fate and provide insights on the molecular pathogenesis of neurodegenerative diseases such as SCAN1 and AT syndromes, which are caused by TDP1 and ATM deficiency, respectively.

PMID:
26578593
PMCID:
PMC4756817
DOI:
10.1093/nar/gkv1196
[Indexed for MEDLINE]
Free PMC Article

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