Final Report Summary - DSBREPAIR (Developmental and Genetic Analysis of DNA Double-Strand Break Repair)
The overall aim of this study is to identify the repertoire of genes required for cells to correctly process DNA double-strand breaks (DSBs), and to investigate how these processes are developmentally regulated. The fact that cells have to carefully coordinate the activities of systems that respond to DSBs is best illustrated by the dual role that DNA breaks have in biology: on the one hand, orchestrated DSBs are essential for life, i.e. DSBs are necessary for recombination in meiotic cells in germline tissue, and in developing lymphocytes DSB repair provides a diverse range of cell surface antigen receptors and are thus critical for a proper immune system. On the other hand, DSBs that result from genetic insults are considered to be among the most dangerous DNA lesions, which can lead to genomic instability, cell death, and in multi-cellular organisms, neoplastic transformation. Despite the fact that many components of the DSB response pathways are known the picture is far from complete. Identifying additional components and eventually the total set of factors that play a role in the DSB response (and how) is one of the major challenges in future research. In addition, remarkably little is known on the cellular response to DNA breaks during animal development: how DSB repair is influenced by cell fate changes and vice versa how DSB induction affects embryonic development. In this project, we successfully generated sensitive reporter-based transgenic animals (C. elegans) that allow us to study the fate of DSBs directly and to systematically test all genes for a role in DSB processing. We also studied DSB repair in the context of gametogenesis and animals development. We identified novel factors that are required to repair DSBs through conventional pathways and studied the interplay between various routes of DSB repair. The main discovery of our research is the identification of a novel pathway of DNA break repair that we termed Polymerase Theta-mediated End joining, as it critically depends on the activity of the A- family polymerase Theta. This pathway acts as a stand-alone pathway on DNA breaks that result from replication barriers, which are not processed by the well-known DSB repair pathways non-homologous end joining or homologous recombination.