Promoters in the Transfer Region of Plasmid F

Abstract

Regulation of the conjugation (tra) genes of IncF plasmids occurs by a complex, 2-stage process. Most IncF plasmids carry 2 fertility inhibition genes, finO and finP, the products of which act in concert to prevent transcription of traJ, a gene which has its own promoter (6, 22). F itself lacks finO but carries both a finP gene and the site at which FinOP regulation occurs, fisO. In turn, the traJ protein (pTraJ) is required for transcription of the major 32-kb traY→Z operon (10,22). The transfer region contains 2 further promoters, that for traM (21,23), and a weak promoter that also transcribes traI and traZ (1,23). There have also been suggestions that the F traT surface exclusion gene has its own promoter (18), as does the traT gene of R100 (16), although the polarity on surface exclusion and traD of Mu insertions into the traYZ operon argues against this (8,10). These regulatory stages were reviewed by Willetts and Skurray (24).