Impaired Repair of Ionizing Radiation-Induced DNA Damage in Cockayne Syndrome Cells

• Published in: Radiation research 2011-04, Vol.175 (4), p.432-443
• Main Authors: Cramers, Patricia, Verhoeven, Esther E, Filon, A. Ronald, Rockx, Davy A. P, Santos, Susy J, van der Leer, Anneke A, Kleinjans, Jos C. S, van Zeeland, Albert A, Mullenders, Leon H. F
• Format: Article
• Language: English
• Subjects: Cell lines; Cell Survival - radiation effects; Cells, Cultured; Cockayne Syndrome - genetics; Cockayne Syndrome - pathology; DNA; DNA damage; DNA Damage - genetics; DNA Repair - genetics; DNA Repair - radiation effects; Dose-Response Relationship, Radiation; Fibroblasts; Humans; Irradiation; Lesions; Radiation damage; Radiation Dosage; REGULAR ARTICLES; RNA; Solar X rays
• ISSN: 0033-7587; 1938-5404
• DOI: 10.1667/RR1972.1

Cockayne syndrome (CS) cells are defective in transcription-coupled repair (TCR) and sensitive to oxidizing agents, including ionizing radiation. We examined the hypothesis that TCR plays a role in ionizing radiation-induced oxidative DNA damage repair or alternatively that CS plays a role in transcription elongation after irradiation. Irradiation with doses up to 100 Gy did not inhibit RNA polymerase II-dependent transcription in normal and CS-B fibroblasts. In contrast, RNA polymerase I-dependent transcription was severely inhibited at 5 Gy in normal cells, indicating different mechanisms of transcription response to X rays. The frequency of radiation-induced base damage was 2 × 10−7 lesions/base/Gy, implying that 150 Gy is required to induce one lesion/30-kb transcription unit; no TCR of X-ray-induced base damage in the p53 gene was observed. Therefore, it is highly unlikely that defective TCR underlies the sensitivity of CS to ionizing radiation. Overall genome repair levels of radiation-induced DNA damage measured by repair replication were significantly reduced in CS-A and CS-B cells. Taken together, the results do not provide evidence for a key role of TCR in repair of radiation-induced oxidative damages in human cells; rather, impaired repair of oxidative lesions throughout the genome may contribute to the CS phenotype.