title: Long-term XPC silencing reduces DNA double-strand break repair.
abstract: To study the relationships between different DNA repair pathways, we established a set of clones in which one specific DNA repair gene was silenced using long-term RNA interference in HeLa cell line. We focus here on genes involved in either nucleotide excision repair (XPA and XPC) or nonhomologous end joining (NHEJ; DNA-PKcs and XRCC4). As expected, XPA(KD) (knock down) and XPC(KD) cells were highly sensitive to UVC. DNA-PKcs(KD) and XRCC4(KD) cells presented an increased sensitivity to various inducers of double-strand breaks (DSBs) and a 70% to 80% reduction of in vitro NHEJ activity. Long-term silencing of XPC gene expression led to an increased sensitivity to etoposide, a topoisomerase II inhibitor that creates DSBs through the progression of DNA replication forks. XPC(KD) cells also showed intolerance toward acute gamma-ray irradiation. We showed that XPC(KD) cells exhibited an altered spectrum of NHEJ products with decreased levels of intramolecular joined products. Moreover, in both XPC(KD) and DNA-PKcs(KD) cells, XRCC4 and ligase IV proteins were mobilized on damaged nuclear structures at lower doses of DSB inducer. In XPC-proficient cells, XPC protein was released from nuclear structures after induction of DSBs. By contrast, silencing of XPA gene expression did not have any effect on sensitivity to DSB or NHEJ. Our results suggest that XPC deficiency, certainly in combination with other genetic defects, may contribute to impair DSB repair.
authors.affiliation: Commissariat à l'Energie Atomique, Laboratoire de Génétique de la Radiosensibilité, Département de Radiobiologie et de Radiopathologie, Direction des Sciences du Vivant, Fontenay-aux-Roses, France. emmanuelle.despras@cea.fr
authors.forename: Emmanuelle
authors.initials: E
authors.lastname: Despras
authors.forename: Petra
authors.initials: P
authors.lastname: Pfeiffer
authors.forename: Bernard
authors.initials: B
authors.lastname: Salles
authors.forename: Patrick
authors.initials: P
authors.lastname: Calsou
authors.forename: Steffi
authors.initials: S
authors.lastname: Kuhfittig-Kulle
authors.forename: Jaime F
authors.initials: JF
authors.lastname: Angulo
authors.forename: Denis S F
authors.initials: DS
authors.lastname: Biard
mesh_terms: D004249:DNA Damage; D000072481:DNA Ligase ATP; D011088:DNA Ligases / Q000378:metabolism; D004260:DNA Repair / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D051747:DNA-Activated Protein Kinase / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D005047:Etoposide / Q000494:pharmacology; D005720:Gamma Rays; D020868:Gene Silencing; D006367:HeLa Cells; D006801:Humans; D034622:RNA Interference
chemical_list: D004268:DNA-Binding Proteins; C101467:XRCC4 protein, human; C086984:XPC protein, human; D005047:Etoposide; D051747:DNA-Activated Protein Kinase; D011088:DNA Ligases; D000072481:DNA Ligase ATP