Flexibility of Vibrio cholerae ToxT in transcription activation of genes having altered promoter spacing.
Cholera, a severe diarrheal disease, is caused by ingestion of the gram-negative bacterium Vibrio cholerae. Expression of V. cholerae virulence factors is highly regulated at the transcriptional and posttranscriptional levels by a complex network of proteins and small noncoding RNAs. The direct activator of transcription of most V. cholerae virulence genes is the ToxT protein. ToxT binds to a 13-bp sequence, the toxbox, located upstream of genes in its regulon. However, the organization of toxboxes relative to each other and to the core promoter elements at different genes varies dramatically. At different ToxT-activated genes a single toxbox may be necessary and sufficient for full activation, or pairs of toxboxes organized as either inverted or direct repeats may be required for full activation. Although all toxboxes are located at positions consistent with a class I promoter architecture, the locations of toxboxes relative to the transcription start site also vary from gene to gene. To further assess the ability of ToxT to activate transcription from different configurations relative to the core promoter elements, we constructed promoter-lacZ fusions having altered spacing both between toxbox pairs and between the promoter-proximal toxbox and the -35 box at five different ToxT-activated promoters. Our results suggest that that ToxT has remarkable flexibility in its positioning as a transcription activator and that different interactions between ToxT and RNA polymerase occur during transcription activation of promoters having different toxbox configurations.
Department of Immunology and Microbiology, Wayne State University School of Medicine, Detroit, MI 48201, USA.
Michelle
M
Bellair
Jeffrey H
JH
Withey
D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D018983:DNA Footprinting; D004269:DNA, Bacterial / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D009154:Mutation; D011401:Promoter Regions, Genetic; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014734:Vibrio cholerae / Q000235:genetics* / Q000378:metabolism
D001426:Bacterial Proteins; D004269:DNA, Bacterial; D014157:Transcription Factors; C075626:tcpN protein, Vibrio cholerae