Transcriptional Organization and In Vivo Role of the Escherichia coli rsd Gene, Encoding the Regulator of RNA Polymerase Sigma D

Abstract

ABSTRACT The regulator of sigma D (Rsd) was identified as an RNA polymerase ς 70 -associated protein in stationary-phase Escherichia coli with the inhibitory activity of ς 70 -dependent transcription in vitro (M. Jishage and A. Ishihama, Proc. Natl. Acad. Sci. USA 95:4953–4958, 1998). Primer extension analysis of rsd mRNA indicated the presence of two promoters, ς S -dependent P1 and ς 70 -dependent P2 with the gearbox sequence. To get insight into the in vivo role of Rsd, the expression of a reporter gene fused to either the ς 70 - or ς S -dependent promoter was analyzed in the absence of Rsd or the presence of overexpressed Rsd. In the rsd null mutant, the ς 70 - and ς S -dependent gene expression was increased or decreased, respectively. On the other hand, the ς 70 - or ς S -dependent transcription was reduced or enhanced, respectively, after overexpression of Rsd. The repression of the ς S -dependent transcription in the rsd mutant is overcome by increased production of the ς S subunit. Together these observations support the prediction that Rsd is involved in replacement of the RNA polymerase ς subunit from ς 70 to ς S during the transition from exponential growth to the stationary phase.