Determining the Protein-Protein Interactions Within the Bacterial mRNA Degradosome and the Regulators of RpoS Under Nitrogen Limiting Conditions

Abstract

Bacteria encounter a range of conditions throughout their lives and must be able to defend themselves against stressful environments. For Escherichia coli, α factors are integral to this adaptation process. These factors and their regulators are therefore prime targets for more specific antibacterial therapies. Some of the α factors are induced under a specific stress to bind RNA polymerase in order to upregulate the genes required to combat the particular stress encountered. RpoS is one such sigma factor and is indispensable for E. coli 's survivial . Integral in facilitating RpoS function are the anti-adaptor proteins IraP, IraM and IraD, and the sRNA's DsrA and RprA, which upregulate RpoS during different stress conditions. In this study we demonstrate that IraP and the sRNA DsrA post-translationally and translationally upregulate RpoS, respectively, during nitrogen-limited conditions. Additionally, we demonstrate that AppY, previously considered only to be a transcriptional activator, possibly interacts directly with SprE as an anti-adaptor to post-translationally upregulate RpoS. Interestingly, SprE has a second function independent of its effects on RpoS levels, which is to assist in mRNA degradation. Although the components responsible for mRNA degradation have largely been discovered and their general functions teased apart, SprE's role in the mRNA degradosome pathway remains unknown. Here we demonstrate via bacterial two-hybrid analysis that SprE possibly interacts directly with the core degradosome component PNPase and transiently, or indirectly with PAPI.