Transcriptional regulation of stress responses by the Universal stress proteins A and C in Escherichia Coli

The Universal stress proteins A and C are small, cytoplasmic proteins that are expressed during stasis and under a wide variety of stress conditions. While their expression has been shown to confer resistance to such stresses, the exact biochemical and physiological function(s) of these paralogs remains unknown. The putative global stress response regulatory roles of UspA and UspC were investigated by characterizing the effects of uspA and/or uspC deletion on (i) survival and (ii) transcriptional activity of genes known to respond to and remediate specific types of stress in Escherichia coli. Transcription levels were quantified in vivo using pUCD615-based promoter::luxCDABE reporter fusions and luminometric assay. Loss of uspA and/or uspC results in increased sensitivity to genotoxic (UV), heat shock (ethanol), and oxidative (peroxide) stress in a non-additive fashion. Strains lacking uspA exhibit hyper-induction of recA, dnaK, katG, and pta/ack transcription in response to genotoxic, heat shock, oxidative, and glucose upshift stresses (respectively), while glnAp2 activity is silenced in the uspA mutant. Strains lacking uspC exhibit the same transcriptional phenotypes as uspA mutants with the following exceptions: dnaK and pta/ack induction is abrogated, and basal levels of dnaK are constitutively elevated. Thus, UspA and UspC regulate stress-responsive genes in distinct and overlapping ways that may offer insight into the diverse phenotypes and sensitivities of usp mutants