Transcription has the capacity to mechanically modify DNA topology, DNA 
structure and nucleosome arrangement. Resulting from ongoing transcription, 
these modifications in turn may provide instant feedback to the transcription 
machinery. To substantiate the connection between transcription and DNA 
dynamics, we charted an ENCODE map of transcription-dependent dynamic 
supercoiling in human Burkitt's lymphoma cells by using psoralen photobinding to 
probe DNA topology in vivo. Dynamic supercoils spread ~1.5 kilobases upstream of 
the start sites of active genes. Low- and high-output promoters handled this 
torsional stress differently, as shown by using inhibitors of transcription and 
topoisomerases and by chromatin immunoprecipation of RNA polymerase and 
topoisomerases I and II. Whereas lower outputs are managed adequately by 
topoisomerase I, high-output promoters additionally require topoisomerase II. 
The genome-wide coupling between transcription and DNA topology emphasizes the 
importance of dynamic supercoiling for gene regulation.