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The molecular basis of selective promoter activation by the σ S subunit of RNA polymerase
Author(s) -
Typas Athanasios,
Becker Gisela,
Hengge Regine
Publication year - 2007
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 - 10.1111/j.1365-2958.2007.05601.x
Subject(s) - regulon , sigma factor , rpos , rna polymerase , biology , genetics , gene , sigma , promoter , protein subunit , transcription (linguistics) , transcription factor , regulation of gene expression , context (archaeology) , specificity factor , computational biology , rna , gene expression , microbiology and biotechnology , linguistics , physics , quantum mechanics , paleontology , philosophy
Summary Different environmental stimuli cause bacteria to exchange the sigma subunit in the RNA polymerase (RNAP) and, thereby, tune their gene expression according to the newly emerging needs. Sigma factors are usually thought to recognize clearly distinguishable promoter DNA determinants, and thereby activate distinct gene sets, known as their regulons. In this review, we illustrate how the principle sigma factor in stationary phase and in stressful conditions in Escherichia coli , σ S (RpoS), can specifically target its large regulon in vivo , although it is known to recognize the same core promoter elements in vitro as the housekeeping sigma factor, σ 70 (RpoD). Variable combinations of cis ‐acting promoter features and trans ‐acting protein factors determine whether a promoter is recognized by RNAP containing σ S or σ 70 , or by both holoenzymes. How these promoter features impose σ S selectivity is further discussed. Moreover, additional pathways allow σ S to compete more efficiently than σ 70 for limiting amounts of core RNAP (E) and thereby enhance Eσ S formation and effectiveness. Finally, these topics are discussed in the context of sigma factor evolution and the benefits a cell gains from retaining competing and closely related sigma factors with overlapping sets of target genes.