The bromodomain protein BRD4 regulates splicing during heat shock

During heat stress cyto-protective genes including heat shock proteins are transcriptionally up-regulated and post-transcriptional splicing is inhibited. In contrast, co-transcriptional mRNA-splicing is maintained. These factors closely resemble the proteotoxic stress response during tumor development. The bromodomain protein BRD4 has been identified as an integral member of the oxidative stress as well as of the inflammatory response. Furthermore, there is evidence for BRD4''s role in splicing regulation; Using RNA-Seq analyses we indeed found a significant increase in splicing inhibition, in particular intron retentions, during heat treatment in BRD4-deficient cells, but not under normal conditions. Subsequent experiments revealed that heat stress leads to the recruitment of BRD4 to nuclear stress bodies, to the interaction with the heat shock factor 1 (HSF1) and to the transcriptional up-regulation of non-coding Sat III RNA transcripts. These findings implicate BRD4 as a central regulator of splicing during heat stress. Since BRD4 is a potent target for anti-cancer therapies, our data linking BRD4 to the splicing machinery and the heat stress response - give additional insight into the mode of action of BRD4 inhibitors. Overall design: WI38 cells have been treated by heatshock and anti BRD4 siRNA and combination.