| Summary: | 碩士 === 國立高雄師範大學 === 生物科技系 === 103 === Three different Dps proteins including Dps1 (BC2011), Dps2 (BC5044) and Dps3 (BC1005) encoded in Bacillus cereus confer cell protection. Dps2 regulated by PerR can be induced against oxidative stress and Dps3 in response to general stress is controlled by σB. However, little is known about the regulation of Dps1 except Dps1 is known to be expressed following the growth stage. In the prior study, we proposed that Dps1 was regulated by PerR despite no typical PerR consensus sequence was found within the promoter of dps1. In this study, we demonstrated a PerR binding site upstream of dps1 coding region via EMSA and DNase I Footprinting in vitro. Inconsistently, Western blotting showed that the expression profile of Dps1 was comparable to the wild-type when dps1 under the control of a truncated promoter with loss of PerR binding site was complemented in B. cereus Δdps1,dps2. Moreover, analysis of β-galactosidase showed deletion of PerR did not affect expression of Dps1. Our data suggest that Dps1 is unlikely governed by PerR in vivo. Additionally, we generated clpX mutant to explore whether the ATP-depend Clp proteases regulate Dps1 through eliminating the degradation of Dps1 during the stationary phase. In consequence, Dps1 was constitutively expressed irrelevant to ClpX, while loss ClpX increased the expression of Dps2 under the minimal nutrition condition. On contrast, indistinguishable expressions of Dps1 and Dps2 in the wild-type and clpX mutant were found in rich medium. In summary, our results showed that PerR and ClpX might not be involved in Dps1 regulation. However, ClpX seems to regulate Dps2 at specific condition for example limited nutrition.
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