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 chemokin es. 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 t he 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 m ethionine residues in the ORF, predicting a primary amino acid structu re, starting at the fourth methionine residue, which includes a possib le signal peptide as well as conserved cysteine residues typical for m ammalian beta chemokines. The RNA transcript is polyadenylated, sugges ting that it can undergo translation within the cytoplasm of an MCMV-i nfected cell, We speculate that expression of the chemokine homolog at late times in the MCMV replication cycle plays a role in MCMV pathoge nesis, possibly by action as a chemotactic agonist or antagonist or by alteration of the activation or differentiation state of a susceptibl e cell such as a macrophage.