Protective role of Cockayne Syndrome B (CSB) protein in maintaining genome integrity in human cells under oxidative stress

Cockayne Syndrome (CS), a progeroid disorder characterised by premature ageing and neurodevelopmental abnormalities, is primarily caused by mutations in the CSB protein, a key component of the transcription-coupled nucleotide excision repair pathway. This study investigates the role of CSB in managing oxidative DNA damage and preserving telomere integrity under oxidative stress. Using CSB-deficient human fibroblasts (CS-B) and matched controls, we exposed cells to acute and chronic oxidative stress via hydrogen peroxide (H₂O₂) and elevated oxygen (40 %) levels. CS-B fibroblasts showed relative resistance to acute oxidative stress in terms of cell death, maintaining viability and displaying limited cell cycle arrest. In contrast, chronic oxidative exposure induced accelerated senescence in CS-B cells, evidenced by increased telomere attrition, senescent morphology, and early activation of senescence-associated β-galactosidase associated with increased DNA damage and aberrant DNA repair. Gene expression profiling revealed downregulation of key DNA repair and cell cycle genes in CS-B fibroblasts following H₂O₂ treatment, indicating impaired damage response pathways. These findings highlight the essential role of CSB in genome maintenance and suggest that its loss contributes to CS pathology through heightened sensitivity to chronic oxidative stress and telomere dysfunction. This work enhances our understanding of CS-related cellular mechanisms and may inform future therapeutic strategies targeting oxidative stress and DNA repair.