Role of Murine Cytomegalovirus US22 Gene Family Members in Replication in Macrophages

Abstract

The large cytomegalovirus (CMV) US22 gene family, found in all betaherpesviruses, comprises 12 members in both human cytomegalovirus (HCMV) and murine cytomegalovirus (MCMV). Conserved sequence motifs suggested a common ancestry and related functions for these gene products. Two members of this family, m140 and m141, were recently shown to affect MCMV replication on macrophages. To test the role of all US22 members in cell tropism, we analyzed the growth properties in different cell types of MCMV mutants carrying transposon insertions in all 12 US22 gene family members. When necessary, additional targeted mutants with gene deletions, ATG deletions, and ectopic gene revertants were constructed. Mutants with disruption of genes M23, M24, m25.1, m25.2, and m128 (ie2) showed no obvious growth phenotype, whereas growth of M43 mutants was reduced in a number of cell lines. Genes m142 and m143 were shown to be essential for virus replication. Growth of mutants with insertions into genes M36, m139, m140, and m141 in macrophages was severely affected. The common phenotype of the m139, m140, and m141 mutants was explained by an interaction at the protein level. The M36-dependent macrophage growth phenotype could be explained by the antiapoptotic function of the gene that was required for growth on macrophages but not for growth on other cell types. Together, the comprehensive set of mutants of the US22 gene family suggests that individual family members have diverged through evolution to serve a variety of functions for the virus.Herpesviruses are large and complex DNA viruses, widely found in nature. Human cytomegalovirus (HCMV), an important human pathogen, defines the betaherpesvirus family. Mouse CMV (MCMV) and rat CMV serve as biological model systems for HCMV. HCMV, MCMV, and rat CMV display the largest genomes among the herpesviruses (13,34,43). These genomes are essentially colinear over the central 180 kb of the 230-kb genomes. Betaherpesviruses, which include the CMVs as well as human herpesviruses 6 and 7, differ from alpha-and gammaherpesviruses by the presence of additional gene families such as the US22 gene family, which are mainly clustered at the ends of the genome (29, 30).The US22 family was first described in HCMV (13). This gene family comprises 12 members in both HCMV and MCMV and 11 in rat CMV. Members of the US22 gene family are characterized by stretches of hydrophobic and charged residues as well as up to four conserved sequence motifs which are specific for betaherpesviruses. Motif I differs between the HCMV US and UL family members (30). In MCMV, m128 and m139 to m143 share the HCMV US-like motif I, while M23, M24, m25.1, m25.2, M36, and M43 share UL-like motif I. Motifs I and II have consensus sequences, while motifs III and IV are less well defined but have stretches of nonpolar residues (18, 24). The m139 to m141 genes contain all four of these motifs, whereas m142 and m143 (and IRS1/TRS1 of HCMV) lack motif II. In addition, m139, m140, m142, and m143 each have an acidic domain, common to he...

Cytomegalovirus-induced embryopathology: mouse submandibular salivary gland epithelial-mesenchymal ontogeny as a model

“…Other than in some intraductal epithelial cells, there is scant evidence of cell death in epithelial or stromal cells. This is consistent with the well-documented CMV suppression of cell death [26][27][28][29][30][31][32][33].…”

Four Distinct Patterns of Memory CD8 T Cell Responses to Chronic Murine Cytomegalovirus Infection

“…M102 is homologous to HCMV UL102, which encodes a helicase-primase component (39,40). m139 belongs to a family of genes implicated in MCMV replication in macrophages (41)(42)(43), and the functions of M38 and m164 are unknown. M45, the source of noninflationary epitopes in both BALB/c and C57BL/6 mice, is important for endothelial cell tropism (44).…”

The Context of Gene Expression Defines the Immunodominance Hierarchy of Cytomegalovirus Antigens

“…Viruses were propagated as described (19) and virus stocks were prepared from M2-10B4 lysates purified on a sucrose cushion as described previously (20). Virus titers were determined on MEFs by plaque assay.…”