Abstract
Human adenoviruses (HAdVs) are widespread pathogens with the capacity to manipulate host cellular pathways, including critical tumor suppressor networks. During oncogenic cell transformation, the adenoviral E1B-55K protein serves as a multifunctional viral regulator that, inter alia, modulates both p53-dependent and -independent pathways - though this function has been disputed in the context of viral infection. Here, we elucidate the dual role of E1B-55K in disrupting host defenses, focusing on its impact on p53 signaling and interferon-stimulated genes (ISGs) during infection. Using RNA-seq and follow-up experimental validation in A549 (p53 wildtype) and H1299 (p53-null) cells infected with wildtype HAdV-C5 or an E1B-55K-deficient mutant, we show that E1B-55K suppresses p53-mediated transcriptional responses. Concurrently, E1B-55K modulates ISG expression in a context-dependent manner. Our results reveal that E1B-55K leverages cellular context to optimize viral replication by targeting a host tumor suppressor and indicate interference with innate immune pathways. Our study thereby uncovers a previously underappreciated aspect of E1B-55K function during infection, offering insights into its repressive activity and solidifying its role as a multifunctional viral oncoprotein with broader implications for the HAdV replication cycle.