Variable pause positions of RNA polymerase II lie proximal to the c-myc promoter irrespective of transcriptional activity.

Transcriptional activation of the c-myc proto-oncogene is mediated by the transition of promoter proximal, paused RNA polymerase II (pol II) into a processive transcription mode. Using a transcription assay which allows the high resolution mapping of transcriptional complexes in intact nuclei, we have characterized the promoter proximal pause positions of pol II. Pol II paused in a nucleosome-free region close to the transcription start site as well as further downstream, between positions +17 and +52. These pause positions were detected in both transcriptionally active and inactive c-myc genes. Pharmacological inhibition of the C-terminal phosphorylation of the large subunit of pol II did not affect the paused transcription complexes, but had an inhibitory effect on transcription of nucleosomal DNA downstream of position +150. The different properties of pol II proximal and distal to the promoter suggest a model in which c-myc transcription is regulated by the activation of promoter bound polymerases.