The focus of our research concerns adenovirus oncoproteins of early regions 1B (E1B) and 4 (E4). These oncoproteins, which are essential for efficient virus replication, cooperate to immortalize cells and cause tumors in newborn rodents.

Two of these—the E1B 55-kilodalton protein and the E4 orf6 protein—act in concert to promote the efficient export of viral mRNA from the nucleus, to block the export of cellular mRNA from the nucleus, and to inactivate key host cell proteins that regulate cell growth and DNA repair. Our work suggests that these viral proteins operate through host cell factors normally involved in mRNA transport.

We have mapped one factor to a small region of human chromosome 21 corresponding to the RUNX1 gene. Ongoing work seeks to identify the contribution of RUNX1 to the outcome of an adenovirus infection.

The E1B 55-kilodalton and the E4 orf6 oncoproteins are also required for adenovirus to replicate in a cell cycle-independent manner. This observation forms a second, related focus of our research. Mutant adenoviruses that cannot regulate messenger RNA transport are able to replicate only by infecting a cell that is in S phase.

The control of both mRNA transport and translation are linked to the cell cycle at the time of infection. We have discovered that the ability to selectively replicate in the S-phase-infected cell is influenced by other oncoproteins of the E4 region. By studying the cellular processes targeted by these oncoproteins for efficient virus replication, we gain a greater understanding of fundamental mechanisms of cellular growth targeted by adenovirus. This property has led to the use of the E1B 55-kilodalton-mutant virus to treat several forms of human cancer.

Our research provides information needed for the rational design and application of such conditionally replicating, oncolytic adenoviruses.