In order to investigate the role of DNA bending on the regulation of σ54-dependent promot- ers, we introduced the CopG binding site between the enhancer-like element and the core promoter of glnAp2, nifLp and glnHp2, without changing the dis- tance in between. The expression activities of these homologous promoters were either activated or re- pressed by the CopG-induced DNA bending in E. coli. In this case, similar regulatory pattern (either acti- vated or repressed) could be observed, when the bending centers from CopG are in integral DNA he- lixes interval, while opposite regulatory pattern could be observed, when the bending centers from CopG are in integral plus a half DNA helixes interval. These results suggested that CopG-induced DNA bending can exert regulatory effects on the transcription of σ54-dependent promoters probably by altering the relative DNA helix phase of 54 RNA polymerase and NtrC.
