The IE86 protein of human cytomegalovirus is an 'immediate early' viral protein that drives cells into S phase, but blocks cell division. In the March 5 Proceedings of the National Academy of Sciences, Song and Stinski describe a microarray analysis of the effects of IE86 expression on the human transcriptome (Proc Natl Acad Sci USA 2002, 99:2836-2841). They infected human foreskin fibroblast cells with a replication-defective adenovirus encoding the IE86 protein, then isolated cellular RNA and hybridized it to oligonucleotide arrays containing about 12,000 human genes. Of these, 64 were activated more than four-fold by IE86 expression; half of these are implicated in cell proliferation and DNA replication. A number of the IE86-induced genes are known targets of the cell-cycle regulator E2F; it remains to be established how IE86-induced genes block cell cycle progression.