The gH glycoprotein of herpesviruses is located on the cell surface in viral-infected cells but is retained in the endoplasmic reticulum (ER) when expressed separately from a recombinant expression vector. These observations suggested the requirement for either a viral function or a viral-induced cellular function which facilitates surface expression of gH, gL fulfills this role in the herpes simplex virus (HSV)-infected cell (J. Virol. 66, 2240-2250, 1992). We have identified the gene product of the UL115 open reading frame (ORF) as the functional homologue of HSV gL in the human cytomegalovirus (CMV) genome. In addition, we have demonstrated that a cellular gene, the human basic fibroblast growth factor receptor (FGFr) will also facilitate some transport of CMV gH to the cell surface. Coexpression in Chinese hamster ovary cells of the gene product of the UL115 ORF or soluble FGFr with C-terminally truncated gH enhanced levels of secreted gH. These studies suggest that the coexpressed molecules act to mask an ER retention signal(s) exposed when recombinant gH is expressed outside of the context of the viral-infected cell.
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