REGULATION OF THE EXPRESSION OF THE TRAM GENE OF THE F-SEX FACTOR OF ESCHERICHIA-COLI

Conjugative F-plasmid transfer is mediated by the transfer (tra) regio n which encodes nearly 40 genes, 25 of which are essential for this pr ocess in Escherichia coli. TraM is required for conjugation and is enc oded on a separate operon between the origin of transfer and the traJ gene. The traJ gene product is the positive regulator of transcription of the 30 kb tra operon, the first gene of which is traY. Using prime r-extension assays and immunoblots on the F plasmid itself and its der ivatives, we demonstrate that F TraM regulates its own expression from two promoters and that it requires TraY as well as expression of the tra operon for maximal traM transcription. traY is the first gene in t he tra operon under the control of the TraJ regulator, which is in tur n negatively regulated by the antisense RNA, FinP, and the FinO protei n. Thus, a control circuit has been established whereby traM is negati vely regulated by the FinOP fertility inhibition system through its re pression of TraJ expression, which adversely affects transcription of the fray gene.