The E4orf6 protein generates an E3 ubiquitin ligase complex with E1B55K but this is not observed for the E4orf6/DBP fusion.

(A) Domain map of DBP and E4orf6 open reading frames. HR: host range, NLS: nuclear localization sequence, NES: nuclear export sequence, NRS: nuclear retention sequence. (B) HEK293 cells were transfected with E4orf6, flag-E4orf6, or flag-E4orf6/DBP and subjected to immunoblot analysis. E4orf6, but not E4orf6/DBP, induces degradation of Mre11 and Rad50 through a complex with E1B55K (C) HEK293 cells were transfected with flag-E4orf6 or flag-E4orf6/DBP and then subsequently mock-infected or Ad5-infected for 24 hours. Immunofluorescence was performed for flag tag (green) or cellular USP7 (magenta). Both proteins are nuclear but only E4orf6/DBP localizes to viral replication centers marked by USP7. (D) HEK293 cells were transfected with flag-E4orf6 or flag-E4orf6/DBP. Immunofluorescence was performed for flag tag (green) or integrated E1B55K (magenta). Only E4orf6 induces relocalization of E1B55K from cytoplasmic aggresomes to the nucleus. Dashed white lines outline the nuclear periphery. White scale bar denotes 10 μm.