74:3842-3851. which in conjunction with the antipeptide antibody that targets its predicted cytoplasmic C-terminal segment, enables simultaneous independent detection of both termini. In cells infected with the recombinant, the US17 N and C termini experienced limited colocalization, with the N-terminal segment not detected in nuclei, supporting the segmentation hypothesis. Consistent with this, a fragment with an apparent molecular size of 10 kDa was detected by immunoblotting. We have recognized the first viral example of a seven-transmembrane protein that is either segmented or expressed in nuclei. Further study will be required to learn the mechanism by which this occurs and the function of the nuclear localizing segment. This likely represents yet another mechanism by which a computer virus has hijacked or altered cellular regulatory pathways for its benefit. Human cytomegalovirus (HCMV) is usually a member of the betaherpesvirus subfamily. HCMV congenital contamination is a leading cause of birth defects, and the NVP-CGM097 computer virus is also a major cause of morbidity and mortality in immunocompromised individuals. As part of its biology, HCMV infects a wide variety of cell types and tissues (examined in reference 22). The computer virus in the beginning enters via the epithelium of the upper alimentary, respiratory, or genitourinary tract to establish contamination. Replication in cytotrophoblasts, the placental cells that form the barrier between maternal and fetal blood circulation systems, NVP-CGM097 may be important in transmission of the computer virus to the fetus (24). Granulocyte-macrophage progenitor cells in bone marrow and peripheral blood monocytes are the chief reservoirs for latent HCMV contamination (32). Differentiation of latently infected monocytes into macrophages prospects to reactivation of lytic contamination (31). This diversity of cellular tropisms and biological activity is the end result of complex interplay between the computer virus and host. The 236-kb HCMV genome is usually predicted to encode at least 165 protein-encoding genes (7, 23), plus recently discovered genes that encode microRNAs (25). Although analysis of individual gene function in HCMV is usually incomplete, at least 117 genes are dispensable for productive replication in fibroblasts (8, 39). A wealth of information makes it clear that a large proportion of HCMV genetic complexity is committed not to fundamental replicative processes but to defining its tissue tropism; optimizing growth in a wide diversity of cell types and cell says; regulating its dissemination from cell-to-cell, tissue-to-tissue, and person-to-person; modulation of innate and acquired immunity; and otherwise contributing to pathogenesis (6). Many of the genes whose functions remain elusive likely play functions in these processes. PITX2 As part of analyzing the DNA sequence of the HCMV unique short (US) region, Weston and Barrell (37) (and extended by Chee et al. [4]) made the important observation that HCMV encodes several independent families of related genes, each family having from 2 to as many as 12 users. Sequences within each gene NVP-CGM097 family are generally highly divergent. This strategy of gene duplication and divergence has been used throughout the betaherpesvirus subfamily, but there is little evidence of it in the alpha- and gammaherpesviruses. We are interested in identifying the diversity of function that would have justified such an expenditure of evolutionary capital. One of these gene families, the US12 family, is a set of 10 contiguous tandemly arranged genes (US12 through US21) encoding distantly related proteins that are each predicted to have seven transmembrane segments (7TM proteins) and to be related to G-protein-coupled receptors (GPCR) (26). US12 family members have been recognized only in the cytomegaloviruses of higher primates (HCMV, chimpanzee cytomegalovirus [CCMV], and rhesus cytomegalovirus [RhCMV]). The US12 gene family has NVP-CGM097 been not been studied in detail. HCMV US18, US19, and US20 are all expressed in infected cells, with the major US18 transcript being expressed as a late gene and the US20 transcript as an early gene (12). Deletion or insertional inactivation of individual NVP-CGM097 US12 family member genes had little or no effect on viral replication in fibroblasts (the US13 deletion resulted in a 10?1 to 10?2 reduction in titer), but.