Transcriptional regulation of MG-149, an osmoinducible lipoprotein gene from Mycoplasma genitalium

Transcriptional regulation remains poorly understood in Mycoplasma genitalium, the smallest self-replicating cell and the causative agent of a spectrum of urogenital diseases. Previously, we reported that MG-149, a lipoprotein-encoding gene, was highly induced under physiological hyperosmolarity conditions. In this study we further analysed MG-149 transcription with a focus on the identification of promoter elements and regulatory mechanisms. We established MG-149 as a genuine osmoinducible gene that exhibited the highest transcript abundance compared with other lipoprotein genes. Using genetic approaches, we demonstrated that the -10 region of the MG-149 promoter was essential for osmoinduction. Moreover, we showed that MG-149 osmoinduction was regulated by DNA supercoiling, as the presence of novobiocin decreased MG-149 expression in a dose-dependent manner. Taken together, these results indicate that DNA supercoiling participates in controlling MG-149 expression during in vivo-like conditions.