Modulates viral and host transcriptional activity to promote viral genome replication. Stimulates viral E2a promoter activity by binding and inducing dimerization of host E2F. During viral infection E1A protein binds to cellular retinablastoma (RB) family members and dissociates these repressors from a complex with E2F proteins. Free E2F is then bound to E4orf6/7 which leads to transactivation of viral E2 promoter, and cellular promoters such as E2F-1 promoter. Activation of cellular E2F targets promote cell cycle S phase and thereby possibly favorises viral DNA replication process. Interacts with host E2F proteins. Belongs to the adenoviridae E4-orf6/7 family.