FIG. 1.

Ikaros and Aiolos suppress c-Myc expression in pre-B cells. DKO pre-B cells were cultivated in the presence of IL-7 (5 ng/ml). The cells were infected with retrovirus expressing Ikaros, Aiolos, and IkarosDN. Infected cells were isolated 24 h later by sorting. Empty vector-infected cells were analyzed as a control. The expression of c-Myc (A), λ5 (B), n-Myc (C), cyclin D3 (D), cyclin D2 (E), p21 (F), and cyclin E (G) was analyzed in the sorted cells by real-time PCR. (H) Expression levels of Ikaros in wild-type pre-B and infected DKO pre-B cells. Cultured wild-type pre-B cells and DKO pre-B cells were lysed for protein analysis. The Ikaros-infected DKO pre-B cells which express a high level of GFP were sorted at 24 h after infection for Western blot analysis. (I) DKO pre-B cells express a higher level of c-Myc than wild-type large pre-B cells. Pre-B cells (B220⁺ CD43⁻ IgM⁻) were isolated by sorting from DKO mice. Pre-B cells in wild-type control mice were further separated based on the forward scatter, and only the large pre-B cells were isolated by sorting. Real-time PCR analysis was carried out to examine c-Myc expression in isolated wild-type large pre-B cells and DKO pre-B cells. The values shown are averages and standard deviations from three independent experiments. The statistical significance was determined by a Student t test (*, P < 0.05; **, P < 0.01).