Interaction of CDK4 and Tax peptides in an eukaryotic two-hybrid assay. A) The coding sequence of CDK4 peptides and a CDK4 deletion mutant were constructed via PCR and assembled into the GAL4 DNA-binding domain-expressing vector. The sequence of the CDK reactive N-terminus of Tax was inserted into the VP16 activation domain-expressing vector. B) To test for interaction, CDK4-containing plasmids were co-transfected with the Tax plasmid into 293 cells and luciferase assays were performed. The mean of three independent experiments is shown.