Functional kCYC protein expression in lungs of kCYC^+/- transgenic mice. (A) Western blotting using total protein and immunoprecipitated protein (using anti-Cdk4 antibodies) isolated from lung tissue. IP indicates immunoprecipitation; TG, kCYC^+/- mice. (B) Kinase assay using lung tissue and GST-Rb as a substrate. (C) Quantitative summary of kinase assays. WT (□) and TG (▪) mice (n = 2). H1 indicates histone H1.