Figure 4.
RNase H overexpression suppresses DNA rearrangement and recombination resulting from Sγ3 transcription. (A) Southern blot analysis of chromosomal regions surrounding the Sγ3 transcription unit. The lacZ::PT7-Sγ3-F strain was transformed with vector or an RNase H expression construct, respectively. Transformants were grown in the presence of 1 mM IPTG for the indicated times and subjected to Southern blot analysis as described above. (B) The lacZ::PT7-Sγ3-K-F strain was transformed with vector, an RNase H expression construct, vector plus a T7 RNAP expression construct, or RNase H plus T7 RNAP expression constructs, respectively. Transformants were grown in the presence of 1 mM IPTG for 30 min, allowed to recover for 1 h, and then plated on Kan-containing LB plates to select for cells carrying the functional kan resistance gene. Relative rates of recombination were calculated and are shown in the graph. Error bars represent the average deviation from three independent experiments.