Transcriptional Pausing Caused by NELF Plays a Dual Role in Regulating Immediate-Early Expression of the junB Gene

Human 5,6-dichloro-1-β-d -ribofuranosylbenzimidazole sensitivity-inducing factor (DSIF) and negative elongation factor (NELF) negatively regulate transcription elongation by RNA polymerase II (RNAPII) in vitro. However, the physiological roles of this negative regulation are not well understood. Here, by using a number of approaches to identify protein-DNA interactions in vivo, we show that DSIF- and NELF-mediated transcriptional pausing has a dual function in regulating immediate-early expression of the humanjunB gene. Before induction by interleukin-6, RNAPII, DSIF, and NELF accumulate in the promoter-proximal region ofjunB , mainly at around position +50 from the transcription initiation site. After induction, the association of these proteins with the promoter-proximal region continues whereas RNAPII and DSIF are also found in the downstream regions. Depletion of a subunit of NELF by RNA interference enhances thejunB mRNA level both before and after induction, indicating that DSIF- and NELF-mediated pausing contributes to the negative regulation ofjunB expression, not only by inducing RNAPII pausing before induction but also by attenuating transcription after induction. These regulatory mechanisms appear to be conserved in other immediate-early genes as well.