Figure 3

Cell line-specific OAS protein expression and enzyme activity. A. HeLa cells were transfected with plasmid constructs encoding the indicated OAS1 variants or the empty control vector. Cells were harvested and lysed at the indicated time after transfection and subjected to immunoblot analysis using the OAS1 specific antibody. The positions of the recombinantly expressed OAS1 isoforms are indicated. The position of the endogenously expressed p42 is indicated by an arrow-head. B. Immunoblot analysis of human OAS proteins in HeLa (AA genotype), HT1080 (AG genotype), and Daudi (GG genotype) cells. Cells were either treated with IFN-α, -β and –γ or left untreated (-) for 24 hours, as indicated. The OAS1 proteins were detected by the monoclonal anti-OAS1 antibody, and the OAS2 and the OAS3 proteins with anti-OAS2 and anti-OAS3 antibodies, respectively. C: Protein extracts from HeLa cells transfected with constructs expressing either p46 or p69. α-tubulin was employed as loading control. Unspecific bands recognized by the antibodies are indicated by *. C. Total OAS enzyme activity of HeLa, HT1080 and Daudi cell lysates treated with IFN-β (+) or left untreated (-). Enzyme activities were determined using ATP as substrate. The reaction products were visualized by Mono Q chromatography. Peaks were integrated and used to calculate the specific enzyme activities using the total protein concentration in each cell lysate. Results are an average of three independent experiments. Error bars represent SD.