Coordinated regulation of gene expression by E ... - Jacobs University

RESULTS
parC) which allows the supercoiling in this strain to be maintained after norfloxacin
treatment at near physiological levels (σ = - 0.073) [Zechiedrich et al., 1997]. In
contrast, the same treatment induces DNA relaxation in LZ41 and hypernegative
supercoiling in LZ54 (Figure 12A). Under these conditions the response of the rrnA P1
promoter is dependent on the fis genotype, implying that there are no significant
variations in FIS levels during the norfloxacin treatment [Rochman et al., 2002]. All the
strains used in the experiment shown in Figure 18 contain FIS. In this genetic
background the activities of ∆61 derivatives of the wild-type and discriminator mutant
promoters both exhibited a strong dependence on superhelical density (Figure 18).
Figure 18: In vivo expression of tyrT promoter constructs.
(A) In vivo expression from tyrT promoter at different superhelical densities. Primer extension product of
transcription from genomic total ribosomal RNA P1 promoters (rrn P1), used as a control, is also shown.
(B) Graphical representation of tyrT transcript intensities.
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