We report that the expression of the Bacillus megaterium bmlP1 gene is subj
ect to negative regulation by the bmlP1 3' flanking region. This repression
occurred both in B. megaterium and in Escherichia coli. When the bmlP1 pro
moter 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 repress
ion on a heterologous gene vt hen fused downstream in either orientation, a
nd 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 w
ithin a 116-bp region immediately following the bmlP1 gene. Possible mechan
isms for this repression are discussed.