Transcriptional regulation at a distance in bacteria.
Transcriptional enhancers are cis-acting DNA elements that are binding sites for regulatory proteins and function at large distances from promoter elements to stimulate transcription. Once thought to be unique to eukaryotes, enhancer-like elements have been discovered in a wide variety of bacteria. The regulatory proteins that bind to these bacterial enhancers must contact RNA polymerase to activate transcription. In principle, interactions between bacterial enhancer-binding proteins and RNA polymerase can occur by either DNA looping or tracking of the enhancer-binding protein along the DNA. Paradigms for each of these methods are found in bacterial systems. Activators of sigma(54)-RNA polymerase holoenzyme contact polymerase by DNA looping, while bacteriophage T4 gp45 functions as a sliding clamp that tracks along DNA until it engages RNA polymerase. Significant advances have been made over the last few years towards understanding the mechanisms by which bacterial enhancer-binding proteins activate transcription, but important aspects of these mechanisms are still poorly defined.
Department of Microbiology, 527 Biological Sciences Building, University of Georgia, Athens, Georgia 30602, USA.
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D000595:Amino Acid Sequence; D004268:DNA-Binding Proteins / Q000235:genetics*; D012321:DNA-Directed RNA Polymerases / Q000378:metabolism; D004742:Enhancer Elements, Genetic; D015964:Gene Expression Regulation, Bacterial; D008969:Molecular Sequence Data; D051877:RNA Polymerase Sigma 54; D012808:Sigma Factor / Q000378:metabolism; D014157:Transcription Factors; D014158:Transcription, Genetic
D004268:DNA-Binding Proteins; D012808:Sigma Factor; D014157:Transcription Factors; D012321:DNA-Directed RNA Polymerases; D051877:RNA Polymerase Sigma 54