MECOM and leukemia: First, in the CRISPRi screen, we treated deactivated-Cas9 (dCas9)-KRAB–expressing cells with dTAGV-1 and simultaneously repressed individual MECOM-regulated cisREs with KRAB to investigate whether the repression of any single cisRE was sufficient to maintain leukemia cells in a CD34+ stem cell–like state in the absence of endogenous MECOM.