Varicella-zoster virus ORF1 gene product is a tail-anchored membrane protein localized to plasma membrane and trans-Golgi network in infected cells.
Varicella-zoster virus (VZV) encodes five genes that do not have herpes simplex virus homologs. One of these genes, VZV open reading frame 1 (ORF1), encodes a membrane protein with a hydrophobic domain at its C-terminus that is predicted to be the transmembrane domain. However, the detailed characterization of ORF1 protein in infected cells has not been reported. Here, we produced mono-specific antibodies against ORF1 protein and characterized the gene products in infected cells. Western blot analyses showed the ORF1 polypeptides had apparent molecular masses of approximately 14-17 kDa. Furthermore, ORF1 was found to be a phosphoprotein by immunoprecipitation assay. In immunofluorescence assays, the VZV ORF1 protein was detected at both the plasma membrane and trans-Golgi network in both VZV-infected and ORF1-transfected cells. Moreover, ORF1 proteins associated with each other to form homodimer, and were incorporated into viral particles. The C-terminal hydrophobic domain was required for the association of ORF1 with the membrane structures, indicating that ORF1 protein is anchored to the membrane thorough its C-terminus, which is a transmembrane domain. Because ORF1 possesses a C-terminal transmembrane domain without an N-terminal signal sequence for its translocation to the ER lumen, ORF1 can be classified as a tail-anchored membrane protein. These results show that the N terminus of ORF1 protein faces the cytoplasm in infected cells and the tegument region in mature virions.
Koshizuka
Tetsuo
T
Laboratory of Virology and Vaccinology, Division of Biomedical Research, National Institute of Biomedical Innovation, 7-6-8, Saito-Asagi, Ibaraki, Osaka 567-0085, Japan.
Sadaoka
Tomohiko
T
Yoshii
Hironori
H
Yamanishi
Koichi
K
Mori
Yasuko
Y
D000818:Animals; D000911:Antibodies, Monoclonal; D002462:Cell Membrane / Q000378:metabolism*; D014645:Herpesvirus 3, Human / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D006801:Humans; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D016366:Open Reading Frames; D014407:Tumor Cells, Cultured; D014764:Viral Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism*
D000911:Antibodies, Monoclonal; D008565:Membrane Proteins; D014764:Viral Proteins