Expression of c-Myc in the hematopoietic system is regulated by posttranscriptional mechanisms. (A) mRNA expression of c-Myc by hematopoietic cells of the bone marrow were measured by qRT-PCR (pooled data of 2 independent experiments; N = 8; mean and standard deviation (SD); no significant differences between HSCs and progenitors according to 1-way analysis of variance followed by Dunnett’s multiple comparison test). (B) Histogram of eGFP-c-Myc fluorescence of HSCs and overlay of eGFP-c-Myc fluorescence of HSCs, multipotent progenitor 1 (MPP1), MPP2, MPP4, and MEPs. The eGFP signal is shown in blue, and the background signal of control cells is in gray. (C) eGFP-c-Myc protein expression of hematopoietic cells of the bone marrow as measured by flow cytometry, expressed as background-corrected median eGFP fluorescence (pooled data of 3 independent experiments; N = 12; mean and SD; 1-way analysis of variance followed by Dunnett’s multiple comparison test: differences between HSCs and MPP2/MPP3/MPP4/common myeloid progenitors [CMP]/granulocyte-macrophage progenitors [GMP]/megacaryocyte-erythroid progenitors [MEP] are significant). (D) eGFP-c-Myc expression of Lin⁻ cells cultured in vitro in the presence or absence of proteasome inhibitor MG-132 and/or translation inhibitor cycloheximide as measured by flow cytometry. (E) Quantification of D. Plotted are background-corrected median eGFP signals (pooled data of 2 independent experiments; N = 8; *P < .05; unpaired 2-tailed t test). For a list of abbreviations of hematopoietic cell types and markers used to identify them, refer to Supplemental Table 1.