Ad5 wildtype and mock infected HeLa cells were grown on glass coverslips and harvested at various times post-infection. The cells were washed twice in phosphate buffered saline (PBS) and subsequently fixed in 4% paraformaldehyde in PBS for 15 min at room temperature. After fixation, the cells were permeabilized with 0.5% Triton X-100 in PBS for 15 min at room temperature. Alternatively, the cells were washed twice with PBS, and permeabilized and fixed simultaneously in 4% paraformaldehyde in PBS containing 0.5% Triton X-100 for 15 min at room temperature. Free aldehydes were quenched by incubation with 25 mM glycine in PBS for 15 min at room temperature. After fixation and permeabilization, the cells were rinsed three times in PBS, blocked in PBS containing 1% bovine serum albumin (BSA) and 0.2% fish skin gelatin (FSG) for 20 min, incubated for 1 h with primary antibodies diluted in PBS containing 1% BSA and 0.2% FSG, washed three times for 5 min in PBS containing 1% BSA and 0.2% FSG and incubated with secondary antibodies for 45 min. Alternatively, primary antibodies were fluorescently labeled with Zenon®-labeling technology (Life Technologies) using Zenon® Tricolor Mouse IgG1 Labeling Kit 1 (For Green, Orange and Deep Red Fluorescence Imaging) according to the manufacturer's instructions. DNA was stained with DAPI (0.07 μg/ml in PBS for 5 min) and the samples were mounted in ProLong® Antifade mounting medium (Life Technologies).