Identification and characterization of the gene products of open reading frame U86/87 of human herpesvirus 6.
The human herpesvirus 6 (HHV-6) immediate early-A locus (IE-A) locates in the position analogous to the human cytomegalovirus (HCMV) major IE (MIE) locus that is well-known to play critical roles in viral infection. Similarly to HCMV MIE, HHV-6 IE-A consists of two genetic units, IE1 and IE2, corresponding to open reading frames U90-U89 and U90-U86/87, respectively. However, the HHV-6 IE-A locus exhibits limited sequence homology with the HCMV MIE locus. In this study, to characterize HHV-6 IE2 gene products, polyclonal antibodies against four domains of the U86/87 open reading frame were generated by immunization of rabbits with bacterially-expressed proteins. Three polypeptides derived from the U86/87 region with apparent molecular masses of 100, 85 and 55 kD were detected in HHV-6-infected cells 3 days after infection, while IE1 polypeptides with apparent molecular mass greater than 170 kD were detectable as early as 8 h. Mapping of the IE2 gene products with the antibodies suggests differential splicing and alternative translation initiation in the IE2 genetic unit. The IE2 products show a mixed cytoplasmic and nuclear localization pattern. In addition, the 437 amino acid carboxyl-terminus domain bound to a DNA fragment containing the putative IE-A promoter. These results suggest that HHV-6 IE2 plays a critical role in transcriptional regulation and viral growth as does HCMV IE2, although it is likely that HHV-6 IE2 has expression kinetics different from HCMV IE2.
D000818:Animals; D000914:Antibodies, Viral / Q000097:blood / Q000276:immunology; D002478:Cells, Cultured; D004268:DNA-Binding Proteins / Q000378:metabolism; D005312:Fetal Blood / Q000166:cytology; D015967:Gene Expression Regulation, Viral; D015654:Herpesvirus 6, Human / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*; D006801:Humans; D017874:Immediate-Early Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism; D007114:Immunization; D015151:Immunoblotting; D008214:Lymphocytes / Q000821:virology; D016366:Open Reading Frames / Q000235:genetics*; D011817:Rabbits; D011993:Recombinant Fusion Proteins / Q000276:immunology; D014158:Transcription, Genetic; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics / Q000276:immunology / Q000378:metabolism
D000914:Antibodies, Viral; D004268:DNA-Binding Proteins; D017874:Immediate-Early Proteins; D011993:Recombinant Fusion Proteins; D014764:Viral Proteins