Wild-type v-Myb and ΔP1 v-Myb transform early progenitors in the presence of growth factors.

(A) Flow cytometry of wild-type and ΔP1 v-Myb cells grown in the presence of TGFα, bFGF, and SCF (day 21) using monoclonal antibodies that recognize multipotent cell surface antigens MEP 26, MEP 21, and MEP17. Negative controls are represented by empty curves. Plots axes are as in Figure 2D. (B) Northern blot analysis in wild-type and ΔP1 v-Myb cells of mRNAs for c-Myb, SCL, GATA-1, C/EBPβ, PU.1, Egr-1, and GAPDH on day 21 and day 30. Two identical blots were sequentially hybridized with SCL, PU.1, and Egr-1 probes, or with c-Myb, C/EBPβ, GATA-1, and GAPDH (loading control) probes.