RESECTION AND MUTAGENESIS OF THE ACID PH-INDUCIBLE P2 PROMOTER OF THEAGROBACTERIUM-TUMEFACIENS VIRG GENE

Transcription of the virG gene initiates from two tandem promoters, de signated P1 and P2, that are located 50 nucleotides apart. Transcripti on of the P2 promoter is induced by extracellular acidity. cis-acting sites required for P2 activity were identified by constructing and ass aying a series of 5' and 3' resections and site-directed nucleotide su bstitutions. Nucleotides between positions -9 and -37 were sufficient for regulated promoter activity. Within this region, nucleotide substi tutions at the predicted -10 and -35 regions strongly reduced P2 expre ssion. In addition, alterations in the region between nucleotides -24 and -32 also eliminated or strongly reduced promoter activity. These d ata suggest that this promoter may be regulated by a positive transcri ption factor that binds to nucleotide residues in this interval.