Organization and Expression of Calicivirus Genes

The application of molecular techniques to the characterization of caliciviruses has resulted in an extensive database of sequence information. This information has led to the identification of 4 distinct genera. The human enteric caliciviruses have been assigned to 2 of these genera. This division is reflected not only in sequence diversity but in a fundamental difference in genome organization. Complete genome sequences are now available for 5 enteric caliciviruses and demonstrate that human and animal enteric caliciviruses are phylogenetically closely related. Currently, there is no cell culture system for the human viruses; therefore, studies have relied on heterologous expression and in vitro systems. These studies have shown that in both human and animal viruses the viral nonstructural proteins are produced from a polyprotein precursor that is cleaved by a single viral protease. The purpose of this article is to provide an overview of the current knowledge of genome structure and gene expression in the enteric caliciviruses.