Generation of DNA single-strand displacement by compromised nucleotide excision repair

• Published in: The EMBO journal Vol. 31; no. 17; pp. 3550 - 3563
• Main Authors: Godon, Camille, Mourgues, Sophie, Nonnekens, Julie, Mourcet, Amandine, Coin, Fréderic, Vermeulen, Wim, Mari, Pierre-Olivier, Giglia-Mari, Giuseppina
• Format: Journal Article
• Language: English
• Published: Chichester, UK John Wiley & Sons, Ltd 29.08.2012; Nature Publishing Group UK; Springer Nature B.V; Nature Publishing Group
• Subjects: Animals; Cell Line; Deoxyribonucleic acid; DNA; DNA Damage; DNA Repair; DNA, Single-Stranded - genetics; DNA-Binding Proteins - genetics; EMBO13; EMBO24; Endonucleases - genetics; Exo1; Humans; Irradiation; Lesions; Mice; Mice, Transgenic; Molecular biology; Mutagenesis; Mutation; Nuclear Proteins - genetics; nucleotide excision repair; Signal transduction; Transcription Factors - genetics; Ultraviolet radiation; Ultraviolet Rays; Xeroderma Pigmentosum Group D Protein - genetics; XPD helicase; XPG endonuclease; γH2AX; Exo1; γH2AX; nucleotide excision repair; XPD helicase; XPG endonuclease
• ISSN: 0261-4189; 1460-2075; 1460-2075
• DOI: 10.1038/emboj.2012.193

Nucleotide excision repair (NER) is a precisely coordinated process essential to avoid DNA damage‐induced cellular malfunction and mutagenesis. Here, we investigate the mechanistic details and effects of the NER machinery when it is compromised by a pathologically significant mutation in a subunit of the repair/transcription factor TFIIH, namely XPD. In contrast to previous studies, we find that no single‐ or double‐strand DNA breaks are produced at early time points after UV irradiation of cells bearing a specific XPD mutation, despite the presence of a clear histone H2AX phosphorylation (γH2AX) signal in the UV‐exposed areas. We show that the observed γH2AX signal can be explained by the presence of longer single‐strand gaps possibly generated by strand displacement. Our in vivo measurements also indicate a strongly reduced TFIIH‐XPG binding that could promote single‐strand displacement at the site of UV lesions. This finding not only highlights the crucial role of XPG's interactions with TFIIH for proper NER, but also sheds new light on how a faulty DNA repair process can induce extreme genomic instability in human patients. Strong tumorigenic effects of a particular mutation in the key nucleotide excision repair factor XPD may not be due to DNA break generation, but caused by inefficient excision steps resulting in long single‐strand gaps and genomic instability.