Ubiquitination, another pathway identified in our list of common genes, is a key component of the immune system, the conjugation of single, or multiple, ubiquitin molecules to a protein targets it for defined subcellular localization, or destruction in the proteasome [28] . Components of the ubiquitin-proteasome system have been shown to be required for the maturation and release of a number of viruses (see review [29] ). In order to investigate the role of ubiquitin-proteasome system in dengue infection, we introduced proteasome inhibitors, MG-132 and ALLN, to the HepG2 dengue infection model [30] . At lower concentrations, both MG-132 and ALLN significantly reduced virus replication in the cell lines by over 50% (Figure 5B ). An examination of the effects of these compounds on the integrity and viability of inhibitor-treated cells using fluorescein diacetate revealed no cytotoxicity at these concentrations ( Figure 5C ). Higher concentrations of the inhibitors had an even greater effect (.90% reduction in pfu/ml) but with a degree of cytotoxicity ( Figures 5B, 5C ).