Nucleotide excision repair roles in R-loops accumulation and telomere maintenance in human cells

Abstract

Genomic instability due the accumulation of DNA lesions is extensively related to processes of aging and carcinogenesis. Therefore, mutations in genes involved in DNA repair lead to syndromes related to premature aging process and cancer susceptibility. In humans, mutations in genes related to nucleotide excision repair (NER) pathway are responsible for xeroderma pigmentosum (XP), with extremely high frequency of skin tumors in regions exposed to sunlight (due to ultraviolet -UV- radiation), and some patients presenting clinical manifestations related to neurodegeneration and premature aging such like in other NER deficiency syndromes as Cockayne syndrome (CS) and trichothiodystrophy (TTD). On the other hand, other factors such as the accumulation of DNA-RNA hybrids structures (R-loops) and deficiencies in telomere maintenance are also related to premature aging phenotypes. Considering the hypothesis that the deficiencies in NER may interfere in transcription process provoking the accumulation of R-loops structures and that NER may have roles in telomere maintenance, we aim to evaluate how human cells holding different mutations in NER genes (that result in diverse phenotypes in relation to premature aging and neurodegeneration (as XP-D, XP/CS and CSB) will respond for these endpoints to the oxidative stress induced by photoactivated methylene blue or the exposure to L-buthionine sulphoximine (BSO, an inhibitor of glutathione synthesis). Finally, the data that will be generate has a great potential to contribute to the comprehension of oxidative stress and DNA repair effects in R-loops accumulation and telomere integrity, eventually establishing a better connection among the different clinical phenotypes caused by NER genes mutations, which are so diverse regarding susceptibility to cancer and premature aging, and better understanding the aging process itself.