Characterization of mitochondrial function in cells from patients with Xeroderma pigmentosum variant to investigate a possible link between DNA damage response and energetic metabolism

• Grant number: 24/03685-9
• Support Opportunities: Scholarships in Brazil - Master
• Start date: August 01, 2024
• End date: February 28, 2026
• Field of knowledge: Biological Sciences - Biochemistry - Metabolism and Bioenergetics
• Principal Investigator: Nadja Cristhina de Souza Pinto
• Grantee: Beatriz Kopel
• Host Institution: Instituto de Química (IQ). Universidade de São Paulo (USP). São Paulo , SP, Brazil
• Associated scholarship(s): 25/00371-6 - Investigation of possible changes in mitochondrial morphology and mitophagy levels in xeroderma pigmentosum variant cell lines, BE.EP.MS

Abstract

All known cellular organisms have DNA repair pathways, essential for maintaining genomic stability. In biological contexts in which it is not possible to repair DNA lesions before transcription or replication events, tolerance mechanisms that allow the continuation of these processes are relevant. Among the damage tolerance mechanisms, the main one is translesion synthesis (TLS), which involves TLS DNA polymerases, such as DNA polymerase eta (DNA pol eta). Loss of function of this protein increases the mutagenic capacity of cyclobutane pyrimidine dimers (CPDs), the main damage to DNA caused by UV radiation, thus causing the disease xeroderma pigmentosum variant (XP-V), whose phenotype is characterized by photosensitivity and elevated rates of skin cancer. The main cellular role of DNA pol eta is to enable the faithful replication of DNA containing CPDs, which is directly related to the phenotype of high rates of cancer in regions exposed to UV. However, recent results from our group have shown that cells from XP-V patients exhibit a basal redox imbalance, which is exacerbated after UV-A irradiation, suggesting that this phenotype may contribute to increased carcinogenesis. Preliminary data from our laboratory showed that the reduced glutathione/oxidized glutathione ratio is diminished in XP-V cells, and UV-A activates the transcription factor NRF2 only in XP-V cells. Since mitochondria play a central role in redox homeostasis, it is relevant to investigate their role in the redox imbalance observed in XP-V cells. Mitochondrial dysfunction has already been observed in other XP complementation groups, such as XP-A and XP-C, which contributes to the loss of cellular homeostasis in these contexts. Thus, this project proposes to investigate whether the absence of DNA pol eta affects the functional integrity of mitochondria using a bioenergetic approach, in order to relate the response to DNA damage and energy metabolism in cells deficient in DNA pol eta.