ZNF521 and infection: To verify if this was the case, K562 cells were subjected to one round of infection with FUIGW-ZNF521, UMG-LV5-ZNF521, UMG-LV6-ZNF521 and UMG-LV11-ZNF521 and the EGFP-positive and negative cells were sorted by flow cytometry (Fig. 7A).