FIG. 8.

Posttranscriptional heat shock induction of YobF. (A) Sequence of the yobF-cspC promoter and coding region. The +1 site of both the longer transcript (position 1905817 of the E. coli K-12 genome) and the shorter transcript (position 1996212 of the E. coli K-12 genome) are denoted by arrows. Possible σ⁷⁰ binding sites are indicated in bold, and nucleotides that are predicted to base pair with the OxyS small RNA are denoted with dots. (B) yobF-cspC mRNA (top) and YobF-SPA protein (bottom) levels in cells exposed to heat shock. Samples were treated as for Fig. 7A. Cells were harvested before transfer (T0) and after 20 min at 30°C or 45°C. (C) YobF-SPA levels in a Δlon mutant strain. Again, cells were harvested from samples kept at 30°C or 45°C for 20 min or before transfer (T0). (D) YobF heat shock induction with and without hydrogen peroxide exposure in MG1655 and an ΔoxyS mutant. Heat shock induction was conducted as described for panel C, except that in some cases, hydrogen peroxide was added to the cells to a final concentration of 250 μM, 10 min prior to heat shock. Northern analysis was performed as described for Fig. 3. The prominent smaller RNA band runs at ∼600 nucleotides, consistent with the expected size of the shorter yobF-SPA transcript. Western blot analysis was performed as stated for Fig. 2. The asterisk denotes a band corresponding to the full-length SPA-tagged YobF protein.