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Novel mode of transcription regulation by SdiA, an Escherichia coli homologue of the quorum‐sensing regulator
Author(s) -
Yamamoto Kaneyoshi,
Yata Katsumori,
Fujita Nobuyuki,
Ishihama Akira
Publication year - 2001
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1046/j.1365-2958.2001.02585.x
Subject(s) - rna polymerase , rna polymerase ii holoenzyme , biology , rna polymerase ii , transcription (linguistics) , transcription factor ii d , sigma factor , microbiology and biotechnology , operon , promoter , general transcription factor , polymerase , rna , gene expression , genetics , gene , mutant , linguistics , philosophy
SdiA, an Escherichia coli homologue of the quorum‐sensing regulator, controls the expression of the ftsQAZ operon for cell division. Transcription of ftsQ is under the control of two promoters, upstream ftsQ P2 and downstream ftsQ P1, which are separated by 125 bp. SdiA activates transcription from ftsQ P2 in vivo . Here, we demonstrate that SdiA facilitates the RNA polymerase binding to ftsQ P2 and thereby stimulates transcription from P2. Gel shift and DNase I footprinting assays indicated that SdiA binds to the ftsQ P2 promoter region between −51 and −25 with respect to the P2 promoter. Activation of ftsQ P2 transcription by SdiA was observed with a mutant RNA polymerase containing a C‐terminal domain (CTD)‐deleted α‐subunit (α235) but not with RNA polymerase containing σ S or a CTD‐deleted σ D (σ D 529). In good agreement with the transcription assay, no protection of P2 was observed with the RNA polymerase holoenzymes, Eσ S and Eσ D 529. These observations together indicate that: (i) SdiA supports the RNA polymerase binding to ftsQ P2; and (ii) this recruitment of RNA polymerase by SdiA depends on the presence of intact σCTD. This is in contrast to the well‐known mechanism of RNA polymerase recruitment by protein–protein contact between class I factors and αCTD. In addition to the P2 activation, SdiA inhibited RNA polymerase binding to the ftsQ P1 promoter and thereby repressed transcription from P1. Gel shift assays indicate weak binding of SdiA to the P1 promoter region downstream from −13 (or +112 with respect to P2). Neither αCTD nor σCTD are required for this inhibition. Thus, the transcription repression of P1 by SdiA may result from its competition with the RNA polymerase in binding to this promoter.