Negative Regulation of Expression of the Bacillus megaterium bmlP1 Gene by the bmlP1 3′ Flanking Region

We report that the expression of the Bacillus megaterium bmlP1 gene is subject to negative regulation by the bmlP1 3′ flanking region. This repression occurred both in B. megaterium and in Escherichia coli. When the bmlP1 promoter was replaced with a heterologous promoter or when the orientation of the bmlP1 3′ flanking region was reversed, the inhibitory effect was still observed. However, the bmlP1 3′ flanking region was unable to exert repression on a heterologous gene when fused downstream in either orientation, and it was incapable of acting in trans. Dot blot and Northern blot analyses revealed that the repression occurred at the RNA level. Deletion analysis showed that the regulatory site responsible for the repression is located within a 116-bp region immediately following the bmlP1 gene. Possible mechanisms for this repression are discussed.