086 the Role of Excision Repair Cross-Complementation Group 8 Protein in the Modulation of Oxidative Stress and Senescent-Associated Secretory Phenotype in Keratinocytes from a Patient Suffering from Cockayne Syndrome

Nucleotide excision repair (NER) is a DNA repair mechanism involving proteins dedicated to the removal of helix-distorting lesions. Defects in Excision Repair Cross-Complementation Group 8 (ERCC8) gene cause the autosomal recessive Cockayne syndrome type A (CSA) characterized by premature aging features. Patients with CS display a short life-span with neurological and cognitive dysfunction and skin photosensitivity. Clinical features cannot be solely attributed to defects in DNA repair. Indeed, CS proteins may have additional functions beyond their role in DNA repair, such as transcription regulation following genotoxic stress and control of oxidative metabolism. Primary keratinocytes from a CSA patient displayed premature aging features, namely premature clonal conversion accompanied by stem cell depletion, high steady-state levels of 8-OH-dG and a senescent-associated secretory phenotype (SASP). CSA keratinocytes were stably transduced with wild type ERCC8 using a retroviral infection method. The exogenous protein was predominantly localized to the nucleus. Gene correction restored the DNA repair capacity of the cells following UV irradiation. Phenotypic reversion was also characterized by: clonal conversion restoration and proper expression of clonal conversion key regulators (p16INK4a and p63), reduction of the steady-state level of 8-OH-dG due to the increased ability to remove 8-OH-dG residues after UV irradiation, and decreased NFkB activity and secretion of SASP mediators. Altogether these findings demonstrate a protective role of CSA against oxidative stress and SASP-mediated inflammatory phenotype.