CSA and CSB play a role in the response to DNA breaks.

Barbara Pascucci,Alessandra Fragale,Eugenia Dogliotti,Mariarosaria D’Errico,Angelo Salvatore Calcagnile,Giuseppe Leuzzi,Eleonora Parlanti,Annapaola Franchitto,Veronica Marabitti

doi:10.18632/oncotarget.24342

Barbara Pascucci, Alessandra Fragale + Show 7 more

Open Access

https://doi.org/10.18632/oncotarget.24342

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Abstract

CS proteins have been involved in the repair of a wide variety of DNA lesions. Here, we analyse the role of CS proteins in DNA break repair by studying histone H2AX phosphorylation in different cell cycle phases and DNA break repair by comet assay in CS-A and CS-B primary and transformed cells. Following methyl methane sulphate treatment a significant accumulation of unrepaired single strand breaks was detected in CS cells as compared to normal cells, leading to accumulation of double strand breaks in S and G2 phases. A delay in DSBs repair and accumulation in S and G2 phases were also observed following IR exposure. These data confirm the role of CSB in the suppression of NHEJ in S and G2 phase cells and extend this function to CSA. However, the repair kinetics of double strand breaks showed unique features for CS-A and CS-B cells suggesting that these proteins may act at different times along DNA break repair.The involvement of CS proteins in the repair of DNA breaks may play an important role in the clinical features of CS patients.

Highlights

Cockayne syndrome (CS) is a rare genetic progeroid disorder characterized by growth and development defects, severe cutaneous photosensitivity, cachectic dwarfism, progressive neurological dysfunction, and precocious aging
Primary fibroblasts were affected by a significant inter-strain variability that is often associated with the use of cells derived from different subjects, a trend towards higher levels of DNA breaks immediately after treatment was noticed in CS cells as compared to cells from healthy subjects (Figure 1A and 1B)
Transformed CS fibroblasts complemented with the wild-type CSA or CSB genes confirmed the results obtained with primary fibroblasts (Supplementary Figure 1) reinforcing a role of CS proteins in the processing of DNA single strand breaks (SSBs)

Summary

Introduction

Cockayne syndrome (CS) is a rare genetic progeroid disorder characterized by growth and development defects, severe cutaneous photosensitivity, cachectic dwarfism, progressive neurological dysfunction, and precocious aging. CS-defective cells show hypersensitivity to UV light, impaired repair of bulky DNA lesions, delayed recovery of RNA synthesis after UV-damage, and enhanced apoptosis after transcription blockage (reviewed in [1]), patients with CS do not present increased cancer risk as expected in DNA repair defective syndromes. A growing body of evidence indicate that, besides the typical NER lesions, CS cells are defective in the repair of a broad range of DNA damage that may account for the clinical symptoms of CS [7]. It www.impactjournals.com/oncotarget is well established that, upon oxidative stress, CS-A and CS-B cells accumulate oxidatively induced DNA damage. CSB has been shown to repair DSBs by homologous recombination (HR) pathways at transcriptionally active sites [18, 19]

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