The finM promoter and the traM promoter are the principal promoters of the traM gene of the antibiotic resistance plasmid R100

finP multicopy repression and traJ multicopy derepression indicate that the ratio of sense to antisense transcripts is important in the regulation of R100 conjugation. The extension of R100 traM transcripts into traJ shows that promoters in traM can affect this ratio, making the regulation of traM transcription important in the regulation of R100 conjugation, Since R100 traM, traY and tral proteins bind to the traM promoter region, we examined traM transcription in R100-1 traM, tray and tral mutants and compared it with traM transcription in both R100-1 and R100. We verified that the traM and finM promoters provide virtually ail the transcripts originating in the R100-1 traM gene. When either is deleted, as in VAR22 or VAR30, the remaining promoter is highly active. We show here that traY positively regulates R100-1 traM transcription, as has been found for F. We found that tral did not regulate R100-1 traM transcription. The measured activity of the native R100 traM promoter was 12% of that in R100-1, whereas the native R100 finM promoter was 45% of that in R100-1. These data and data from the R100-1 tray and tral mutants show that the activities of the two promoters Varied independently.