Identification of a CDK4 region important for direct Tax interaction. A) For binding assays, CDK4 mutants were constructed via PCR and cloned into the mammalian expression vector pcDNA3.1MycHis. B) CDK4 and its mutants were translated in vitro and reacted with S-agarose-coupled Taxwt. As a control, translated proteins were also incubated with uncoupled S-Agarose. Examples of resulting phosphorimager scans are shown. C) The diagram shows the mean Tax binding and standard deviation of three independent experiments that were quantitatively evaluated.