Characterization and expression of a glycoprotein encoded by the Epstein-Barr virus BamHI I fragment

The most abundant polyadenylated viral transcripts in the Epstein-Barr virus (EBV)-associated tumor nasopharyngeal carcinoma are a family (apparent sizes, 4.8, 5.2, 6.2, and 7.0 kb) of highly spliced cytoplasmic RNAs expressed from the BamHI-I and-A regions of the viral genome in an antisense direction with respect to several viral lytic functions encoded within the same region and concerned with the lytic cycle of the virus. We have called these complementary-strand transcripts. They are also expressed in B cells, including Burkitt's lymphoma and EBV-immortalized marmoset cell lines, and tumors generated in cottontop tamarins in response to EBV infection, but at a lower level. The complete structure of the major 4.8-kb RNAs (seven or eight exons) was determined in this study; the larger, but related, transcripts appear to be produced by differential splicing. The transcriptional promoter for the major complementary-strand transcripts, located in BamHI-I, contains several well-characterized transcriptional control elements (E2A, SP1, and AP1) and is functionally active in both B lymphocytes and epithelial cells. It appears to be a bifunctional viral promoter, as it also contains the initiation codon for a gene (BILF2) that encodes a glycoprotein that is expressed off the other strand. Splicing events create a number of small AUG-initiated open reading frames, one ofwhich has homology to functionally significant regions of the EBV-encoded nuclear antigen 2 and to E2 (in papillomavirus). The complex nature of these transcripts and their potential role in the virus association with malignancy are considered.

Section: Cat Activitymentioning

confidence: 99%

Complex nature of the major viral polyadenylated transcripts in Epstein-Barr virus-associated tumors

Smith¹,

Gao²,

Karran³

et al. 1993

“…The envelope of Epstein-Barr virus (EBV), like that of all herpesviruses, includes multiple unique glycoprotein species. Among those mapped to their open reading frames (ORFs) in the virus genome (1) and characterized at least biochemically are gp350/220, the product of the BLLF1 ORF (2); glycoproteins gp85, gp42, and gp25, respective products of the BXLF2 (7,21), BZLF2 (14), and BKRF2 ORFs (33), which make up the EBV gH-gL-gp42 complex; gp78, the product of the BILF2 ORF (16); gN, the product of the BLRF1 ORF (12); gM, the product of the BBRF3 ORF (12); and gp150, the product of the BDLF3 ORF (11,20). Functions have been ascribed to gp350/220, which is the viral attachment protein that binds the virus to CR2 or CD21 (19,30), and to the gH-gL-gp42 complex, which interacts with HLA class II molecules on B cells (27) and is involved in virus penetration through the membranes of both B cells and epithelial cells (6,13,17,31,32).…”

mentioning

confidence: 99%

“…Lack of expression of gp150 in cells carrying recombinant virus episomes. To confirm that expression of gp150 had been disrupted in cells that contained only recombinant episomes, the cells were induced with anti-human immunoglobulin, labeled with [ 3 H]glucosamine, and immunoprecipitated, as previously described (31), with an antipeptide antibody, anti-gp150, which corresponded to the carboxyl-terminal residues 219 to 232 of gp150 (20), and with the following monoclonal antibodies (MAbs): 72A1 to gp350/220 (9), E2A5 to gp78 (16), and F-2-1 to gp42 within the gH-gL-gp42 complex (14). With the appropriate MAbs, the glycoproteins gp350 and gp78 and the gp85 (gH)-gp42-gp25 (gL) complex could be immunoprecipitated from cells expressing recombinant virus proteins.…”

mentioning

confidence: 99%

Epstein-Barr Virus Recombinant Lacking Expression of Glycoprotein gp150 Infects B Cells Normally but Is Enhanced for Infection of Epithelial Cells

Borza

Hutt-Fletcher

1998

Glycoprotein gp150 is a highly glycosylated protein encoded by the BDLF3 open reading frame of Epstein-Barr virus (EBV). It does not have a homolog in the alpha- and betaherpesviruses, and its function is not known. To determine whether the protein is essential for replication of EBV in vitro, a recombinant virus which lacked its expression was made. The recombinant virus had no defects in assembly, egress, binding, or infectivity for B cells or epithelial cells. Infection of epithelial cells was, however, enhanced. The glycoprotein was sensitive to digestion with a glycoprotease that digests sialomucins, but no adhesion to cells that express selectins that bind to sialomucin ligands could be detected.

“…Many functions of these glycoproteins in the alphaherpesviruses have been elucidated (28), and some of these proteins, notably glycoprotein B (gB), gH, and gL, have known homologs in the gammaherpesviruses (13,14,24,45). However, most of the glycoproteins encoded by the gammaherpesviruses appear to be unique to this subfamily (16,18,19,22,26,34,40).…”

mentioning

confidence: 99%

Identification and characterization of murine gammaherpesvirus 68 gp150: a virion membrane glycoprotein

Stewart

Janjua

Pepper

et al. 1996

Self Cite

Murine gammaherpesvirus 68 (MHV-68) is a naturally occurring virus of murid rodents which displays pathobiological characteristics similar to those of other gammaherpesviruses, including Epstein-Barr virus (EBV). However, unlike EBV and many other gammaherpesviruses, MHV-68 replicates in epithelial cells in vitro and infects laboratory strains of mice and therefore provides a good model for the study of gammaherpesviruses. Studies of sequences around the center of the MHV-68 genome identified a gene (designated BPRF1 for BamHI P fragment rightward open reading frame 1) whose putative product had motifs reminiscent of a transmembrane glycoprotein. All other gammaherpesviruses have a glycoprotein in this genomic position, but the BPRF1 gene showed sequence homology with only the EBV membrane antigen gp340/220. Biochemical analysis showed that the product of BPRF1 was a glycoprotein present on the surface of infected cells, and immunoelectron microscopy showed that it was present in the virus particle. In addition, antibodies to the BPRF1 product raised by using a bacterial fusion protein neutralized the virus in the absence of complement. The predominant molecular weights of the protein were 150,000 and 130,000. Pulse-chase analysis and endoglycosidase-H digestion showed that the 130,000-molecular-weight form was a precursor of the 150,000molecular-weight form, and cell surface labelling showed that the 150,000-molecular-weight form alone was on the cell surface. We therefore named the protein gp150. Since gp150 is the first virion-associated glycoprotein and neutralizing determinant of MHV-68 to be characterized, it provides a valuable tool for the future study of virus-host interactions.