Human cells deficient in transcription-coupled repair show prolonged activation of the Jun N-terminal kinase and increased sensitivity following cisplatin treatment
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PURPOSE: The Jun N-terminal kinases (JNKs) are activated by many biological, physical, and chemical stimuli, including the chemotherapeutic agent cisplatin. The primary pathway that repairs cisplatin-DNA adducts is nucleotide excision repair (NER). Xeroderma pigmentosum (XP) cells from complementation group C (XP-C) are competent in the transcription-coupled repair (TCR) pathway of NER but deficient in global genomic repair (GGR), Cockayne's syndrome (CS) cells are deficient in TCR but have normal GGR, and XP-A cells are deficient in both TCR and GGR. We used NER-deficient human fibroblasts to study the role of DNA damage in the activation of JNK and cell death following cisplatin treatment. MATERIALS AND METHODS: JNK-1 activity and clonogenic survival were examined in normal and NER-deficient human fibroblasts following cisplatin treatment. RESULTS: Cisplatin induced a transient increase in JNK-1 activity of about tenfold in normal and XP-C fibroblasts, which declined to about two- to threefold 24 h after treatment. In contrast, the activation of JNK-1 was persistent in XP-A and CS fibroblasts at 24 h after treatment and CS cells and XP-A cells, but not XP-C cells, were more sensitive to cisplatin than normal cells. CONCLUSIONS: These results suggest that a deficiency in the TCR pathway of NER results in amplified and prolonged JNK activation due to persistent damage within the transcribed strand of active genes. Further, it is this amplified and prolonged JNK activation that correlates with cisplatin-induced cell death.
