My laboratory studies the human DNA tumor virus, adenovirus (Ad). Adenovirus has proven to be an excellent model system to study the regulation of cellular proliferation, gene expression, and host responses to virus infection. Recombinant Ad vectors also are promising agents for therapeutic gene delivery for both short term and long term treatment of a variety of inherited and acquired diseases. Our research is focused in two general areas. First, we study how viral early proteins regulate cellular growth properties and gene expression. Second, we study how infectious virus is assembled and use this information to generate novel vectors for human gene therapy.
Adenovirus regulation of cellular growth and gene expression
The broad objective of this research is to understand how the regulation of gene expression by specific transcription factors impacts on the proliferative capacity of cells and the growth properties of DNA tumor viruses. The model system that we study is the regulation of the E2F family of transcription factors by adenovirus infection. E2F transcription factors are key players in the regulation of proliferation, apoptosis, and differentiation. The central role that the E2F family plays in the regulation of cell growth and death is underscored by the fact that the E2F-retinoblastoma tumor suppressor regulatory cascade is found mutated or deregulated in virtually all human cancers. The regulation of gene expression by E2Fs makes life or death decisions for the cell, and impacts on two key growth suppression pathways, the Rb pathway and the p53 pathway. E2Fs are regulated at multiple levels and by different mechanisms. Ad proteins impact on many of the processes that regulate E2F activity. We are studying how Ad E1A and E4-ORF6/7 proteins regulate the transcription properties of E2F family members including the recruitment of host factors to viral and cellular promoter regions, the regulation of E2F subcellular distribution and protein stability, and E2F regulation of cell cycle progression. We have found that the Ad E4-ORF4 protein induces cell cycle growth arrest and we are pursuing the mechanism of action of this viral product. Lastly, the E4-ORF3 protein remodels nuclear domains referred to as PML oncogenic domains or PODs. We are studying how the E4-ORF3 protein directs this effect and how this relates to virus and cellular growth properties.
Adenovirus assembly and viral vectors for gene therapy.
The broad objectives of this research are to study the fundamental mechanism that directs virus assembly during the late stages of Ad infection, and to develop new Ad vectors for human gene therapy and novel approaches to produce these vectors. Ad vectors offer a number of important advantages for use in gene therapy including wide virus tropism, the ability to efficiently direct gene expression in dividing and non-dividing cells, the capacity to accommodate large gene inserts, and a readily tractable system to produce virus in abundant quantities. The use of high capacity Ad vectors, that is Ad genomes that lack all viral coding sequences, has greatly enhanced Ad vector efficacy. We are developing novel means to generate high capacity Ad vectors utilizing Ad-AAV (AAV, adeno-associated virus) hybrid viruses. This approach allows for the efficient and rapid production of high capacity Ad vectors. The production of high capacity Ad vectors relies on the use of a helper virus. We are developing novel approaches to regulate the production of such helper viruses during Ad vector production. Finally, we are studying the virus assembly process. We have defined viral DNA sequences that direct the packaging of Ad DNA into virus particles during the final stages of virus infection and we are pursuing the analysis of viral and cellular proteins that mediate the packaging process.