To test whether pUL21a interacts with cyclin A during HCMV infection, we performed an immunoprecipitation assay on cell lysates infected with control wildtype virus expressing free GFP (ADgfp) or recombinant HCMV expressing GFP-tagged UL21a (ADgfpUL21a) (Fig. 1C). This evidence concerns the gene CCNA2 and cytomegalovirus infection.