Late expression of a beta chemokine homolog by murine cytomegalovirus.

A gene (HJ1) present in murine cytomegalovirus (MCMV) encodes an open reading frame (ORF) whose predicted amino acid sequence shows homology to the beta (or C-C) class of chemotactic cytokines known as chemokines. The region of homology is located in the carboxyl-terminal portion of the 116-amino-acid ORF. A 0.9-kb RNA transcript corresponding to the HJ1 gene is expressed in MCMV-infected fibroblasts and macrophages as a member of the late kinetic class of virally encoded transcripts. A transcriptional start site is located between the third and fourth methionine residues in the ORF, predicting a primary amino acid structure, starting at the fourth methionine residue, which includes a possible signal peptide as well as conserved cysteine residues typical for mammalian beta chemokines. The RNA transcript is polyadenylated, suggesting that it can undergo translation within the cytoplasm of an MCMV-infected cell. We speculate that expression of the chemokine homolog at late times in the MCMV replication cycle plays a role in MCMV pathogenesis, possibly by action as a chemotactic agonist or antagonist or by alteration of the activation or differentiation state of a susceptible cell such as a macrophage.