Infection with the US21 deletion mutant resulted in selective impairment of many late phase Tp3 and Tp5 (Temporal protein profile 3 and 5) HCMV proteins (Weekes et al., 2014), for example UL32 and UL99/pp28, and elevated expression of pUS20, whereas the HCMV US12-21 block mutant did not recapitulate this effect (Figure 7, with further proteomic data searchable in Excel spreadsheet Supplemental file 1). This evidence concerns the gene TMPO and infection.