Delineation of the regulatory region sequences of Agrobacterium tumefaciens virB operon.
A virB-lacZ translational fusion was constructed to monitor expression of the Agrobacterium tumefaciens virB operon. Expression of the fusion gene was dependent on the presence of pTiA6 virA, virG, and a plant factor acetosyringone. Analysis of deletion mutants, constructed by exonuclease Bal31 digestion, showed that 68 residues upstream of the virB transcription initiation site was necessary for its expression. A TT----CC substitution at positions -62 and -61 led to a 7 fold reduction in virB expression. The virB upstream region contains a tetradecameric sequence, dPuT/ATDCAATGHAAPy (D = A, G or T; H = A, C or T), that is conserved in the non-transcribed regions of all vir genes. Alteration of the position of this sequence relative to the promoter region sequences had a drastic negative effect on virB expression.
Das
A
A
Department of Biochemistry, University of Minnesota, St Paul 55108.
Pazour
G J
GJ
D001483:Base Sequence; D005798:Genes, Bacterial; D008969:Molecular Sequence Data; D009152:Mutagenicity Tests; D009876:Operon; D010957:Plasmids; D012045:Regulatory Sequences, Nucleic Acid; D012231:Rhizobium / Q000235:genetics*; D012689:Sequence Homology, Nucleic Acid