Project Summary Replication fork repair is essential for cell survival and stability of genetic material. In humans, inefficiency of repair is associated with cancer proneness, neurological, immunological, developmental defects and premature aging. For microbial pathogens, the ability to repair DNA damage is required for survival of bacterial pathogens and promotes genetic change that can contribute to antibiotic resistance and persistence of infection. The long-term goal of our studies is a more complete mechanistic understanding of the repair of replication forks and how it affects genomic stability. This will be accomplished using the genetic system of Escherichia coli, whose physiology is well understood. A central interest is how bacterial cells signal difficulties in replication to facilitate repair and how this is integrated with other aspects of bacterial growth. By biochemical and genetic analysis, this work will elucidate how a newly discovered conserved DNA helicase protein, YoaA, interacts with the replisome to overcome barriers in replication. This study will specifically address the influence of RNA transcription and DNA protein complexes on replication and genomic instability and what mechanisms are used to overcome conflicts between replication and transcription machinery. The regulatory pathway controlled by stringent starvation protein, SspA, will also be explored to discover how it impacts DNA metabolism. Because all cells repair DNA in fundamentally similar ways by evolutionarily related pathways, these studies using microbial model organisms should reveal mechanisms applicable to repair of DNA in human cells. In addition, because the DNA damage response in microbial pathogens plays a role in toxin production, antibiotic resistance and persistence of infection, this work could provide new information important for the treatment of infectious disease.