Regulation of sigma factor competition by the alarmone ppGpp.
Many regulons controlled by alternative sigma factors, including sigma(S) and sigma(32), are poorly induced in cells lacking the alarmone ppGpp. We show that ppGpp is not absolutely required for the activity of sigma(S)-dependent promoters because underproduction of sigma(70), specific mutations in rpoD (rpoD40 and rpoD35), or overproduction of Rsd (anti-sigma(70)) restored expression from sigma(S)-dependent promoters in vivo in the absence of ppGpp accumulation. An in vitro transcription/competition assay with reconstituted RNA polymerase showed that addition of ppGpp reduces the ability of wild-type sigma(70) to compete with sigma(32) for core binding and the mutant sigma(70) proteins, encoded by rpoD40 and rpoD35, compete less efficiently than wild-type sigma(70). Similarly, an in vivo competition assay showed that the ability of both sigma(32) and sigma(S) to compete with sigma(70) is diminished in cells lacking ppGpp. Consistently, the fraction of sigma(S) and sigma(32) bound to core was drastically reduced in ppGpp-deficient cells. Thus, the stringent response encompasses a mechanism that alters the relative competitiveness of sigma factors in accordance with cellular demands during physiological stress.
Jishage
Miki
M
Department of Cell and Molecular Biology-Microbiology, Göteborg University, 405 30 Göteberg, Sweden.
Kvint
Kristian
K
Shingler
Victoria
V
Nyström
Thomas
T
D001426:Bacterial Proteins / Q000235:genetics*; D001667:Binding, Competitive; D017931:DNA Primers / Q000737:chemistry; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D012321:DNA-Directed RNA Polymerases / Q000235:genetics* / Q000378:metabolism; D004926:Escherichia coli / Q000235:genetics* / Q000254:growth & development; D017353:Gene Deletion; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics; D006159:Guanosine Tetraphosphate / Q000235:genetics / Q000378:metabolism*; D009154:Mutation; D010957:Plasmids; D011401:Promoter Regions, Genetic / Q000235:genetics; D012808:Sigma Factor / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D013489:Suppression, Genetic; D014158:Transcription, Genetic / Q000235:genetics; D001616:beta-Galactosidase / Q000235:genetics / Q000378:metabolism
D001426:Bacterial Proteins; D017931:DNA Primers; D004268:DNA-Binding Proteins; D012808:Sigma Factor; D006159:Guanosine Tetraphosphate; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases; D001616:beta-Galactosidase