Cell-cycle regulators affect c-Myb activity. Chicken HD-11 macrophage cells were transfected with plasmids expressing c-Myb plus combinations of cyclin D1 and CDK6, as indicated at the top. After 2 days, RNA was prepared and analyzed by Northern blotting for expression of the Myb-inducible Mim1 gene (top) or beta-actin as an RNA loading control (middle). Aliquots of the samples were also analyzed for c-Myb protein expression by Western blotting using anti-Myb antibodies (bottom).