ANALYSIS OF HUMAN-HERPESVIRUS-6 U3 GENE, WHICH IS A POSITIONAL HOMOLOG OF HUMAN CYTOMEGALOVIRUS UL-24 GENE

The US22 gene family was first discovered in human cytomegalovirus (HC MV) and contains several conserved amino acid motifs. Human herpesviru s 6 (HHV-6) also encodes several genes belonging to the US22 family, i ncluding the U3 gene (a positional homolog of HCMV UL24). Because the gene products of the US22 gene family function as gene regulators in g eneral, we analyzed the HHV-6A U3 gene. Six transcripts with different molecular weights of 7.5-1.8 kb were detected by Northern blot analys is using a U3-specific probe. Sequence analyses of the respective cDNA clones and primer extension experiments revealed that the U3 gene enc oded the 2.0- and 3.5-kb transcripts and had no splicing within the U3 gene region. By immunofluorescence testing using antibodies raised to a fusion protein of MBP (maltose-binding protein) and us, the us vira l antigen was detected as early as 24 h p.l. in HHV-6A-infected U373 c ells. The antigens were found in cytoplasmic granules, preferentially in the endoplasmic reticulum. Moreover, cotransfection assay using a l uciferase gene expression system revealed that the U3 gene product was capable of activating the human immunodeficiency virus long terminal repeat promoter in CV1 cells. (C) 1998 Academic Press.