Figure 5

Effect of RecA variants on gene transcription. (A) The scheme represents the effect of RecA persistently bound to DNA on transcription: when RecA binds to DNA and then dissociates, the transcription of lacZ gene is normal. When RecA is persistently bound to DNA, the transcription is blocked. (B) Transcription was assessed by measuring the β-galactosidase activity of MG1655 recA::Cm cells transformed with pQE-80L plasmid derivatives containing each of the seven recA variants and induced by 0.05 mM IPTG. The ratios of β-galactosidase activity in the presence of the variant versus β-galactosidase activity in the presence of EcRecA, used as a reference, were calculated for 3 different biological experiments. These ratios are represented as a histogram. The strains analysed are RecA + strain (green dot filled bar), ΔrecA strain (unfilled bar), ∆recA strain producing EcRecA (green filled bar, it is the reference but is presented for visual comprehension) and ∆recA strains producing the variants PaRecA, DrRecA, EcPa, EcRecAV1 and EcRecAV2 (green dot filled bars). NS indicated a non-significant p-value (from the one sample t test compared to 1, the EcRecA value), * indicates a significant p-value < 0.05 and ** a significant p-value < 0.005. Error-bars indicate SD.