Struktur/Funktions-Beziehungen der sigma S-haltigen "Stress"-RNA-Polymerase in Escherichia coli
Final Report Abstract
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 recognise clearly distinguishable promoter DNA determinants, and thereby activate distinct gene sets, known as their regulons. In summary, we could demonstrate how the principle sigma factor in stationary phase and in stressful conditions in Escherichia coli, σs (RpoS), can specifically target its large regulon in vivo, although it is known to recognise the same core promoter elements in vitro as the housekeeping sigma factor, σ70 (RpoD). Variable combinations of cis-acting promoter features and trans-acting protein factors determine whether a promoter is recognised by RNAP containing σs or σ70, or by both holoenzymes. For how these promoter features impose σs-selectivity we could provide precise hypotheses. Moreover, additional pathways, as e.g. the induction of the σs-binding Crl protein, allow σs to compete more efficiently than σ70 for limiting amounts of core RNAP (E) and thereby enhance Eσs formation and effectiveness. Finally, we could also discuss these topics 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.
Publications
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Typas, A., and R. Hengge (2005) Differential ability of σs and σ70 of Escherichiacoli to utilise promoters containing half or full UP-element sites. Mol. Microbiol. 55, 250- 260.
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2006 Athanasios Typas: Deciphering the way σs-containing RNA polymerase (Eσs) targets its promoters in Escherichia coli (Freie Universität Berlin).
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Typas, A., and R. Hengge (2006) Role of the spacer between the -35 and -10 region in σs promoter selectivity in Escherichia coli. Mol. Microbiol, 59, 1037-1051,
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Typas, A., S. Stella, R.C. Johnson, and R. Hengge (2007) The -35 sequence location and the Fis-sigma factor interface determine σs selectivity of the proP(P2) promoter in Escherichia coli. Mol. Microbiol. 63, 780-796.
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Typas, A., and R. Hengge (2005) Promoter features that confer selectivity for as-containing RNA polymerase. FASEB Conference on Mechanism and Regulation of Prokaryotic Transcription, Saxtons River, VE, USA.
