Beta-galactosidase assay. Detection of the activity of β-galactosidase was carried out using the β-Galactosidase Reporter Gene Staining Kit from Sigma-Aldrich, following the manufacturer’s protocol. Twenty-four hours after transfection of the plasmids (as indicated in Figure 5) in 293-T cells, the cells were washed three times with PBS and lysed with lysis buffer. Mock-infected 293T cells were used as controls. The samples were normalized to the sample amount of total protein. The β-Galactosidase activity in the sample was calculated taking into consideration the OD, final reaction volume, the absorbance of 1mM for an optical path of 1cm, and the incubation period (tmin). For the assays involving isopropyl-thio-b-D-galactopyranoside (IPTG), a final concentration of 0.4mM of IPTG was used. IPTG was added to the supplemented medium and left overnight. Each experiment was performed in triplicate and an average value obtained.