HUMAN CYTOMEGALOVIRUS OPEN READING FRAME UL11 ENCODES A HIGHLY POLYMORPHIC PROTEIN EXPRESSED ON THE INFECTED CELL-SURFACE

Human cytomegalovirus (HCMV) open reading frame (ORF) locates within a polymorphic region of the viral genome identified previously by a res triction-fragment-length-polymorphism We report here that ORF UL11 enc odes a polymorphic protein expressed on the surface of HCMV-infected c ells. First, we determined the nucleotide sequence of ORF UL11 from te n strains and compared it among the strains. Out of 205 amino acids co nsisting of the predicted N-terminal region beside the putative transm embrane stretch in strain AD169, 88 residues were divergent on more th an one strain. In contrast, the predicted C-terminal side including th e putative transmembrane domain was identical at the amino acid sequen ce level. In addition, the number and location of predicted cysteine r esidues were also conserved. Next, we screened a cDNA library from HCM V-infected cells and obtained a cDNA clone containing the full-length ORF UL11. Finally, we identified the gene product of UL11 on the surfa ce of HCMV-infected cells by FAGS analysis with polyclonal antibodies generated against a glutathione S-transferase/UL11 fusion protein. The fusion protein contained a region within the N-terminal side next to the predicted transmembrane stretch. These results indicate that the N -terminal side of UL11 protein containing variable amino acid residues protrudes from the infected cell surface.