A Bacterial Enhancer Functions to Tether a Transcriptional Activator Near a Promoter

• DOI: 10.1126/science.1970441
• Publication Date: 2006-10-05T22:10:14Z
• Authors: Andrew Wedel; David S. Weiss; David Popham; Peter Dröge; Sydney Kustu
• Keywords: DNA, Bacterial; 0303 health sciences; Binding Sites; Transcription, Genetic; DNA, Superhelical; PII Nitrogen Regulatory Proteins; Transposases; DNA-Directed RNA Polymerases; Templates, Genetic; Nucleotidyltransferases; DNA-Binding Proteins; 03 medical and health sciences; Enhancer Elements, Genetic; Bacterial Proteins; Glutamate-Ammonia Ligase; DNA Transposable Elements; Trans-Activators; Promoter Regions, Genetic; Plasmids; Transcription Factors

The nitrogen regulatory protein NtrC of enteric bacteria activates transcription of the glnA gene by catalyzing isomerization of closed complexes between RNA polymerase and the glnA promoter to open complexes. NtrC binds to sites upstream of glnA that have properties of eukaryotic transcriptional enhancers. NtrC-binding sites were found to facilitate open complex formation when these sites and the glnA promoter were located on different rings of a singly linked catenane, but not when the two rings were decatenated. The results provide evidence that NtrC contacts RNA polymerase-promoter complexes in a process mediated by formation of a DNA loop. NtrC-binding sites serve to tether NtrC near the glnA promoter, thereby increasing the frequency of collisions between NtrC and polymerase-promoter complexes.