Using viruses as tools to elucidate the molecular mechanism for transport into the nucleus

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All eukaryotic cells have a distinct nucleus containing, among other things, the genetic blueprint of the organism. Carrying out the instructions contained in the genetic blueprint requires trafficking of molecules between the cytoplasm and the nucleus – a process known as nuclear transport. This trafficking is essential to all eukaryotic cells, and it regulates many aspects of cell physiology. Despite the obvious importance of nuclear transport and several recent advances in this field, numerous aspects of its molecular mechanism, its structural basis, and its regulation remain elusive. The long-term objective of my research program is to elucidate the mechanisms by which macromolecules enter the nucleus. Because many viral pathogens undergo replication within the nucleus, and therefore must deliver their genome and sub-viral particles into the nucleus of their host cells, we are using viruses as tools to understand the molecular mechanisms for nuclear transport. At the same time, a detailed characterization of the nuclear import of viral genomes is an important step in the development of anti-viral therapy that may successfully resolve viral diseases by interrupting entry of the viral genome into the nucleus of infected cells. The viruses we are currently studying include two significant human pathogens: influenza A virus, the causative agent of the common flu, and hepatitis B virus, which causes acute and chronic hepatitis. Two other non-human pathogenic viruses that we are studying are baculovirus, which is extensively used as a eukaryotic expression system for the production of biologically active proteins in biomedical research, and a mice parvovirus, which preferentially targets and kills cancer cells and could be developed for anti-cancer therapy. In our studies, we use a combination of structural, functional, biochemical, and genetic approaches. In addition, we extensively use high-resolution electron microscopy to track the movement of viruses within their host cells and their entry into the nucleus. Findings from these studies will shed new light on the fundamental mechanisms of nuclear transport, and will make significant contributions to understanding the transport of viruses into the nucleus, and more generally the delivery of DNA to the nucleus, which is also an essential step in transfection and gene delivery in gene therapy. Therefore, our studies of nuclear trafficking of viruses could also help developing efficient transfection techniques and gene therapy vectors.