J. Bacteriol., 11 1996, 6389-6393, Vol 178, No. 21
Copyright © 1996, American Society for Microbiology

In vitro transcriptional analysis of TyrR-mediated activation of the mtr and tyrP+3 promoters of Escherichia coli

J Yang, H Camakaris and AJ Pittard
Department of Microbiology, The University of Melbourne, Parkville, Victoria, Australia.

In order to understand the mechanism by which the TyrR protein activates transcription from the mtr and tyrP+3 promoters, we have carried out in vitro transcription experiments with supercoiled DNA templates. We have shown that addition of the histone-like protein HU or integration host factor (IHF) greatly inhibited the transcription from the mtr and tyrP+3 promoters. In the presence of phenylalanine, the wild-type TyrR protein, but not a mutant TyrR protein (activation negative), was able to relieve the HU- or IHF-mediated inhibition of transcription. In contrast, the alleviation of the HU- or IHF-mediated transcription inhibition by the wild-type TyrR protein did not occur when a mutant RNA polymerase with a C-terminally truncated alpha subunit was used to carry out the transcription reaction.

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