SUMMARY Salmonella enterica serovar Typhimurium is a major cause of foodborne illness in the USA and worldwide. During the initial stages of infection, S. Typhimurium invades gut epithelial cells. Expression of genes required for invasion is controlled by a group of transcription factors encoded with the SPI-1 pathogenicity island. We have recently mapped the regulatory targets of these transcription factors. The majority of the regulatory interactions we identified have not been previously described. Thus, the regulatory network associated with invasion is considerably more complex than previously appreciated. Moreover, our work strongly suggests an important role for regulatory RNAs during invasion. Of particular interest is the regulatory RNA STnc520, whose expression is coordinated with that of other invasion genes, and which has been suggested to be important for establishing an infection in three animal models, based on data from high-throughput transposon screens. Here, we will determine the requirement for STnc520 for S. Typhimurium to invade epithelial cells, both in vitro and in vivo. We will also identify direct regulatory targets of STnc520. Thus, we will establish the role of STnc520 during invasion, laying the foundation for future studies of this and other regulatory RNAs that promote invasion.

NARRATIVE Salmonella enterica serovar Typhimurium is a major cause of foodborne illness in the USA and worldwide. We will determine the requirement for STnc520, a regulatory RNA, for S. Typhimurium to invade epithelial cells, both in vitro and in vivo. We will also identify direct regulatory targets of STnc520, thus establishing the role of STnc520 during invasion.