Figure 4.

Requirement of RNase HI for the repression of RnlA activity by RnlB. (A) Wild-type (WT) or ΔrnhA cells harboring pBAD33-Flag-rnlA were grown in LB medium until the OD₆₆₀ reached approximately 0.3, and then treated with or without 0.2% arabinose. Duplicate measurements were performed and similar results were obtained for each measurement; (B) WT or ΔrnhA cells harboring pBAD33-Flag-rnlA were grown until the OD₆₀₀ reached 0.5, and then treated with (+) or without (–) 0.2% arabinose. Total RNAs were extracted at the indicated times and subjected to northern blotting with probes for ompA (upper panel) and lpp (middle panel). Ethidium bromide-stained 16S rRNA is shown as a loading control (bottom panel); (C) WT or ΔrnhA cells harboring pBAD33-Flag-rnlA were treated with 0.2% arabinose for 5 min when the OD₆₀₀ reached 0.5, and then total RNAs were extracted at the indicated times after addition of rifampicin to a final concentration of 500 µg/mL and subjected to northern blotting with probes for ompA and lpp mRNAs. Triplicate experiments were performed and similar results were obtained for each experiment. The time required for a 50% reduction was taken as a half-life (t_1/2) of each mRNA shown below the figure.