Effects of overexpression of c-
myc, CDK2, CDK4, and CDK6 on GATA-2–induced growth suppression of Ba/F3 cells. (A) Ba/F3/GATA-2/ER clones each transfected with an expression vector of c-myc, CDK2, CDK4, CDK6, or an empty vector were cultured with or without 1 μM estradiol. Total number of viable cells was counted by trypan blue dye exclusion method at the time indicated. Similar results were obtained from at least 3 independent clones in each transfectant. The results are shown as means ± SD of triplicate cultures. (B) The cells of Ba/F3/GATA-2/ER overexpressing c-myc were cultured with 1 μM estradiol and subjected to Northern blot analysis on the expression of CDK4, Skp2, and Cul1 at the times indicated. (C) The expression levels of p21WAF1 and p27Kip1proteins were examined by Western blot analysis before and after the 48-hour culture with 1 μM estradiol in mock- and c-myc–transfected Ba/F3/GATA-2/ER. (D) CDK2 activities were evaluated before and after the 48-hour culture with estradiol in mock- and c-myc–transfected Ba/F3/GATA-2/ER with immune complex kinase assays by using Histone H1 as a substrate. The results shown in panels B, C, and D are representative of 3 independent experiments.
