Cytomegalovirus genes: their structure and function.

During the past several years, studies have indicated that cytomegalovirus (CMV) genes can be grouped into two broad categories; those essential for replication in cell culture and those dispensible for virus replication. The latter group of genes are likely to be important for pathogenesis and host-virus interactions. As the field progresses, the need to utilize and establish biological systems capable of addressing gene function during a natural infection of cells in culture, or in the infected animal, is becoming more apparent. Herein, we describe the current status of some of those systems, what has been learned and where these studies may lead. Specifically, we address studies that assess mechanisms of gene activation and function in biologically relevant systems. These include (i) the identification of genes dispensible for replication in cell culture, (ii) the use of dispensible regions of the CMV genome to manipulate genetic information for assessing gene function and activation, and (iii) the identification of a related group of essential loci important for replication of human CMV (HCMV) DNA and what is presently known of the function of those genes during HCMV infection.