ASXL1 mutation is a gain-of-function mutation. The ASXL1 truncating mutant (ASXL1^aa1-587) but not wt ASXL1 recruit BRD4. BRD4 acetylates H3K122 and activates pTEFb leading to phosphorylation (P; activation) of RNA pol II. This results in enhanced transcription. Professional illustration by Patrick Lane, ScEYEnce Studios.