Fig. 8: Model to explain aberrant TOP2 activity as a driver of ATM-deficient thymic malignancies.

TOP2 activity associated with genome organization and transcription throughout the genome can accidentally result in DSBs (top). Additionally, DSBs can arise as a consequence of TOP2 activity derived from genomic reorganization associated to V(D)J recombination, and in particular, the mechanism of RAG scanning to find its RSS targets (bottom). These DSBs concur with RAG-mediated DSBs, increasing the probability of oncogenic translocations to occur. Efficient repair of TOP2-induced DSBs mediated by either TDP2 or ATM-dependent pathways, together with the checkpoint and apoptotic functions of ATM, strongly limit the oncogenic potential of these lesions.