Hematopoietic development involves the coordinated activity of differentiation and cell cycle
regulators. In current models of mammalian cell cycle control, E2f activators (E2f1, E2f2, and
E2f3) are portrayed as the ultimate transcriptional effectors that commit cells to enter and
progress through S phase. Using conditional gene knock-out strategies, we show that E2f1–
3 are not required for the proliferation of early myeloid progenitors. Rather, these E2fs are
critical for cell survival and proliferation at two distinct steps of myeloid development. First …