Repair of topoisomerase-mediated and oxidative-stress induced DNA damage: novel factors and implications on neuronal function. (360G-Wellcome-091043_Z_09_Z)

DNA topoisomerases (Topos) regulate DNA topology ahead of important cellular processes such as transcription, replication, and repair. Topos generate transient DNA breaks in which the Topo is attached to DNA via a covalent phosphotyrosyl bond. Failure to re-ligate these intermediates leads to persistent DNA breaks, which ultimately needs to be repaired. One such repair mechanism involves the hydrolytic cleavage of the phosphodiester bond between the stalled Topo and DNA. The prototype enzyme for such an activity is TDP1, which is also involved in the repair of a variety of oxidative 3 -termini and mutation of which is associated with the neurological disorder SCAN1. Despite this important catalytic function fulfilled by TDP1, it remains the only human enzyme that displays this activity. Here, we aim to (1) characterise and identify novel mechanisms for the repair of DNA topoisomerase-mediated and/or oxidative stress-induced DNA breaks, using a combined approach of yeast genetics and bi ochemical analysis (employing synthetic oligonucleotide substrates). (2) Define the impact of defective repair of oxidative and Top1-mediated DNA breaks on neural cell fate. In particular, we aim to examine the impact on mitochondrial genome stability, using a combination of biochemical, microscopical, and whole animal approaches.