As we also wanted eventually to test this effect in the context of virus infection (see below), we used detection of insoluble PCNA, which acts as a robust direct surrogate for BrdU incorporation [35]–[38] as a marker of cellular DNA synthesis because BrdU incorporation cannot be used to assay cellular DNA synthesis in the context of HCMV infection for two reasons. This evidence concerns the gene PCNA and cytomegalovirus infection.