FIG. 7.

Model for transcriptional regulation of junB by DSIF- and NELF-mediated pausing. Before induction, DSIF and NELF cause RNAPII pausing in the promoter-proximal region of junB, where chromatin structure is decondensed and permissive for PIC assembly (for details, see Discussion). After IL-6 stimulation, STAT3 binds to the promoter and 3′ enhancer regions and increases the efficiency of both PIC assembly and transcription elongation, allowing the polymerase to reach the 3′ end of the gene, possibly by recruiting P-TEFb or other proteins with elongation activation activity. However, DSIF- and NELF-mediated pausing persists in the promoter-proximal region and acts to reduce the maximal level of its expression. Two possible mechanisms for attenuation by NELF are presented.