Characterization of Transcription Coupled Repair deficient cells in response to oxidative stress

Abstract

The repair of DNA bases modified by reactive oxygen species (ROS) through the base excision repair (BER) pathway is widely known in literature. However, evidence suggests these types of lesion can also be repaired through the transcription coupled repair (TCR) pathway of the nucleotide excision repair (NER), which repairs lesions that block the progression of the transcription machinery (bulky lesions). The transcription stalled by oxidated base lesions is presented as a plausible hypothesis to explain the neurodegeneration phenotype of Cockayne Syndrome (CS), a genetic disease related to the compromising of the TCR-NER pathway. Mutant CSB cells have been characterized in regards to their UV light sensibility, agent known to cause bulky lesions, due to their deficiency on the CSB protein, important for the TCR-NER pathway. So, this work proposes to characterize the response of CSB mutant cells to oxidative stress causing agents, from the transcription stall by oxidated bases. Furthermore, evidences suggest the role of the TCR-NER proteins in the resolution of R-loops, structures formed by DNA:RNA hybrids. The increase in R-loops, and DNA double strand breaks as a consequence, presents as a plausible mechanism to cause death in cells deficient in this pathway. Therefore, this work also proposes to quantify R-loops of CSB cells under oxidative stress, in search to explain the clinical phenotypes of neurodegeneration and early aging found in CS patients.Furthermore, evidences suggest the role of the TCR-NER proteins in the resolution of R-loops, structures formed by DNA:RNA hybrids. The increase in R-loops, and DNA double strand breaks as a consequence, presents as a plausible mechanism to cause death in cells deficient in this pathway. Therefore, this work also proposes to quantify R-loops of CSB cells under oxidative stress, in search to explain the clinical phenotypes of neurodegeneration and early aging found in CS patients.