Oferta TFM | ID 43

DNA damage is largely inevitable and constitutes a major cause of genomic instability, a hallmark of cancer as well as a feature of neurological disorders, premature aging, inflammatory signalling and developmental abnormalities. To maintain genome integrity, cells have evolved complex DNA damage detection and repair pathways. However, despite their high efficiency, some DNA lesions escape repair and must instead be tolerated. This is particularly important during chromosome replication, as unrepaired DNA lesions can stall replication forks, thereby compromising faithful genome duplication and leading to genomic instability. Cells cope with these challenges through evolutionarily conserved DNA damage tolerance (DDT) mechanisms that mediate the bypass of unrepaired DNA lesions blocking replication forks. These mechanisms ensure the completion of chromosome replication in the presence of DNA damage and are therefore essential for maintaining genome integrity. DDT is mainly mediated by either homologous recombination-dependent template switching, which is largely error-free, or translesion DNA synthesis (TLS), which is frequently error-prone. These pathways are interconnected, regulated by post-translational modifications of PCNA, and mediated, respectively, by the budding yeast protein Rad5 (the human orthologue HLTF), an E3 ubiquitin ligase with ATPase/helicase activity, and by specialized TLS DNA polymerases.

Despite considerable progress, many aspects of DDT remain poorly understood. In particular, little is known about how DDT components are regulated, how cells choose between different DNA damage bypass pathways, or how DDT is coordinated with other cellular processes. The aim of this project is to address these questions and improve our understanding of how eukaryotic cells respond to DNA damage-induced replicative stress to preserve genome stability.

This Master's Thesis (TFM) project will focus on the regulation and function of DDT mechanisms and their role in maintaining genome integrity. It addresses a topic of broad interest with important implications for both basic research and biomedicine, while providing multidisciplinary training. The project will be carried out in the Chromosome and Genome Stability Laboratory at the CBM (CSIC-UAM) and will address four objectives: (1) subcellular relocalization of DDT proteins under stress conditions; (2) identification and characterization of post-translational modifications relevant to DDT regulation and function; (3) modulation of DDT mechanisms by different cellular pathways; and (4) crosstalk between DDT pathways and other processes involved in cellular homeostasis.The project will combine molecular biology, genetics, cell biology and biochemistry approaches. Because the mechanisms under study are evolutionarily conserved, the genetically tractable yeast Saccharomyces cerevisiae will be used as the experimental eukaryotic model. Indeed, S. cerevisiae is a powerful model system for investigating fundamental molecular mechanisms and has been instrumental in elucidating the molecular basis of numerous diseases. As part of their scientific training, the student will learn to design experiments, analyse and interpret results, critically evaluate the scientific literature, and communicate research findings through seminars and scientific publications.

References

• Lehmann CP, González-Fernández P, Tercero JA (2024) Nucleic Acids Res. 52:1156-1172.
• Jiménez-Martín A, Saugar I, Joseph CR, Mayer A, Lehmann CP, Szakal B, Branzei D, Tercero JA (2020) Sci. Adv. 6:eaaz3327.
• Waizenegger A, Urulangodi M, Lehmann CP, Clarisse-Reyes TA, Saugar I, Tercero JA, Szakal B, Branzei D (2020) Nat. Commun. 11:5746.
• Lehmann CP, Jiménez-Martín A, Branzei D, Tercero JA (2020) Curr. Genet. 4:1045-1051 (review).
• Saugar I, Jiménez-Martín A, Tercero JA (2017) Cell Rep. 20:1553-1562.
• Ortiz-Bazán MA, Gallo-Fernández M, Saugar I, Jiménez-Martín A, Vázquez MV, Tercero JA (2014). Cell Rep. 9: 460-468.