Abstract
The faithful replication of DNA and mechanisms of repair are essential cellular functions. In the model bacterium, Escherichia coli the mechanisms that protect DNA and ensure accurate replication have shown to be conserved across species. In this work we detail an SOS-independent response to DNA damage that links the signals of DNA replication and nutrient starvation through the regulation of the gene iraD. The master regulator of DNA replication, DnaA and the Stringent Starvation Protein, SspA are transcription factors that modulate iraD expression. We look further into the molecular mechanisms by which SspA is sensing and responding to DNA damage during starvation and healthy growth conditions. SspA physically interacts with RNA transcription machinery to act as a transcriptional activator and modulate R-loop formation during RNA exit or transcription termination. Previous work established sspA∆ as a growth defect suppressor of holC∆, a replisome associated protein. Our work seeks to explain this suppression by sspA∆’s increased prevalence of R-loop structures that are advantageous for replication restart. HolC directs the replisome to sites of ssDNA through the interaction with SSB that coats ssDNA across from R-loop structures. Taken together, our work shows that SspA is a protein with diverse functionality in its response to starvation conditions, DNA damage, and DNA replication dynamics in E. coli.