To analyze the effects of SUMO-1 overexpression on viral DNA synthesis, U373-Neo and U373-SUMO-1 cells transduced with either shUbc9 or non-silencing lentiviral particles (see below) or non-transduced, were seeded at a density of 5610 4 per well in 24well plates. The next day, cells were infected with HCMV AD169 at an MOI of 1 PFU/cell. At 72 h post-infection (p.i.), cells were collected and total DNA was extracted using the QiAmp DNA Extraction Kit (Qiagen). The levels of viral DNA were then determined by qPCR and normalized to the cellular b-globin gene copies as described [46] .