Mechanisms and Genetic Consequences of Break-Induced Replication.

PROJECT SUMMARY During normal cell metabolism, exogenous and endogenous factors cause double-strand DNA breaks (DSBs) that result in genome instability. DSB repair is critical for cell viability, but some DSB repair processes exacerbate genome instability. Break-induced replication (BIR) is a unique DSB repair mechanism associated with telomerase-independent telomere maintenance and genome instability. Although BIR is evolutionarily conserved from phages to mammals, BIR in mammals has only recently gained attention. Because BIR involves non-reciprocal copying of the template through conservative DNA synthesis, errors in this process occur and can lead to catastrophic genome instability in the form of genomic duplications, translocations, and rearrangements. BIR, which is less frequent than other DNA repair mechanisms, is context-specific. Because its role in mammalian cells was only recently discovered, and BIR has often been overlooked in favor of more common DNA repair mechanisms, here we argue that an in-depth study of BIR mechanisms is needed. My long-term goal is to understand the role of BIR in promoting genome instability and maintaining telomere lengths. To understand the mechanisms and genetic consequences of BIR, I will take a multidisciplinary approach that combines cell biology, biochemistry, and genomics. My goals for the next 5 years are (1) to determine the mechanisms by which BIR is regulated at telomeres and transcriptionally active loci in the genome and (2) to develop new experimental tools and techniques for studying BIR. Collectively, the proposed projects will elucidate the connection between BIR, genome instability, and telomere elongation. Further, we will identify the upstream regulatory mechanisms that initiate BIR coupled with transcription. Ultimately, these studies will advance our understanding of the relationship between transcription and genome instability.