Adenovirus early region 4 protein (Ad E4 protein)

Adenovirus early region 4 (E4) proteins are a group of multifunctional regulatory proteins encoded by the E4 transcription unit of the adenovirus genome. This complex includes several distinct open reading frames (ORFs), most notably E4orf1, E4orf3, E4orf4, and E4orf6, each playing critical roles in the viral life cycle and host cell modulation [6, 12]. These proteins facilitate viral DNA replication, regulate the transition from early to late gene expression, and promote the export of viral mRNAs while shutting off host cell protein synthesis [9, 10]. A key mechanism involves E4orf6 forming an E3 ubiquitin ligase complex with the viral E1B-55K protein to degrade cellular targets like p53 and the Mre11-Rad50-Nbs1 (MRN) complex, thereby subverting the host's DNA damage response and apoptotic pathways [4, 8, 19]. In therapeutic contexts, E4orf4 is of significant interest for its ability to induce p53-independent, cancer-specific apoptosis, making it a potential tool or template for novel oncology treatments [1, 2]. Conversely, the E4 region is often deleted in recombinant adenovirus vectors used for gene therapy to minimize host immune responses and cellular toxicity [7, 20]. While direct inhibitors of E4 proteins are primarily in the research stage, they represent vital targets for developing specific anti-adenoviral therapies, especially for immunocompromised patients [11].

Other names

Adenovirus E4 proteinsEarly region 4 proteinsE4orf1E4orf2E4orf3E4orf4E4orf6E4orf6/7

Inhibition of viral replication; induction of p53-independent apoptosis; inhibition of DNA damage response; proteasome-mediated degradation of host proteins.