Promyelocyte self-renewal requires nuclear localized Hhex. (A) Growth curves showing expansion of virally transduced (GFP⁺) lineage marker–negative BM cells following infection with control virus (MIG) or viruses encoding Hhex, the ERT2 domain, or a Hhex-ERT2 fusion cultured in the presence of IL-3 with or without tamoxifen (Tam) to induce nuclear localization of ERT2. Data are representative of 3 separate experiments. (B) FACS analysis showing expression of Mac-1 and GFP of liquid cultures as in panel A at day 21 of culture.