SwrA extends DegU over an UP element to activate flagellar gene expression in Bacillus subtilis .

requires an UP element and is activated by a heteromeric transcription factor of DegU and SwrA. Our evidence suggests that SwrA oligomerizes DegU over the DNA to allow RNA polymerase to interact with DegU and the UP element simultaneously. Heteromeric activator complexes are known but poorly-understood in bacteria and we speculate they may be needed to resolve spatial conflicts in the DNA sequence.