PLZF-RARα increases the proliferative capacity of hematopoietic progenitors. (A) PLATE 293T retroviral producer cells were transfected with MPG, MPG-PLZF, and MPG-PLZF-RARα retroviral vectors, and whole-cell lysates were Western blotted with PLZF (2A9) antibody. (B) Murine lin⁻ hematopoietic progenitors were infected with MPG or MPG-PLZF-RARα retrovirus and plated in methylcellulose under myeloid-promoting conditions. Cell-cycle profiles of day-8 colonies were assessed after a 3-hour BrdU pulse. Cells were stained with anti–BrdU-APC antibody and 7-amino-actinomycin D and analyzed by flow cytometry. (C) Human lineage-depleted (Lin⁻) CD34⁺ progenitors from cord blood were infected with MPG or MPG-PLZF-RARα retrovirus and maintained in liquid culture. Cell counts were performed over a period of 40 days. (D) PLZF-RARα directly binds to the promoters of several key regulators of G1/S transition. RNA was extracted from MPG or MPG-PLZF-RARα–expressing murine colonies at day 8 and the expression of PLZF-RARα proliferation target genes (c-Myc, Dusp6, Cdkn2d, and Cdkn1b) was analyzed by qRT-PCR. Data are expressed as mean ± SEM of 3 independent experiments (**P < .05).