Adenovirus type 5 early region 1B protein (E1B) (Ad5 E1B)

The Adenovirus type 5 early region 1B protein (E1B) is a critical early gene product of the Human Adenovirus C serotype 5, consisting of two primary isoforms: E1B-19K and E1B-55K [3, 13, 33]. E1B-19K functions as a viral Bcl-2 homolog that prevents premature host cell death by inhibiting pro-apoptotic proteins like BAX and BAK, thereby ensuring sufficient time for viral replication [1, 10, 35]. E1B-55K is a multifunctional oncoprotein that binds to and inactivates the tumor suppressor p53, preventing p53-mediated cell cycle arrest and apoptosis [2, 5, 37]. Additionally, E1B-55K cooperates with the viral E4orf6 protein to form an E3 ubiquitin ligase complex that targets p53 and other host proteins, such as the Mre11-Rad50-Nbs1 (MRN) complex, for proteasomal degradation [8, 15, 19, 29]. In biotechnology, the E1B gene is a central focus for oncolytic virotherapy; for instance, E1B-55K-deleted adenoviruses (e.g., Onyx-015 and H101) are designed to selectively replicate in and lyse p53-deficient tumor cells while sparing normal cells [6, 14, 21, 23]. However, the therapeutic use of E1B-modified vectors is often challenged by robust host innate immune responses and the complexity of p53-independent viral replication mechanisms [11, 12, 25].

Other names

E1B-55KE1B-19KEarly region 1B proteinAdenovirus 5 E1B proteinHAdV-C5 E1B

Oncolytic viruses such as Onyx-015 and H101 utilize a deletion of the E1B-55K gene to achieve tumor selectivity, theoretically restricting viral replication to p53-deficient cancer cells while allowing functional p53 in normal cells to suppress viral growth [6, 20, 21, 23].