First, in contrast to vector control and pig APOBEC3F overexpressing co-cultures, PERV pol gene DNA was difficult to amplify from the genomic DNA of 293T cells that had been cocultured with APOBEC3G-expressing PK-15 cells ( Figure 5B and every significant sampling point in our Q-PCR experiments). Taking this together with the observation that APOBEC3G does not effect PK-15 virus production (similar RT levels were observed in cell-free supernatants in the presence or absence of APO-BEC3G; data not shown), we infer that APOBEC3G restricts PERV transmission after virus production but before provirus integration (i.e., between entry and integration). APOBEC3G may restrict PERV at an early reverse transcription stage, possibly by interfering with primer binding, DNA synthesis and/or integration Is Deamination-Independent. PERV-specific Q-PCR data using genomic DNA prepared from 293T cells co-cultured with PK-15 clones expressing APOBEC3G (G; triangles), APOBEC3G-E259Q (GE259Q; circles) or empty vector (V; squares). Two datasets, each with an independent PK-15 clone in three replica co-culture wells, were collected in parallel and averaged for each data point. One standard error of the mean is shown. The experimental parameters are identical to those used in Figure 1B as shown recently for APOBEC3G and HIV-1 substrates (e.g., [30, [52] [53] [54] [55] ).