EBV Conference 2008 Guangzhou - Baylor College of Medicine

90 (RegID: 1207)
Mindy Gore
Institution: Louisiana State University Health Sciences Center-Shreveport
e-mail: mgore1@lsuhsc.edu
BDLF2 ENCODES THE ELEVENTH EBV VIRION ENVELOPE GLYCOPROTEIN AND IS
DEPENDENT ON BMRF2 FOR PROCESSING AND TRANSPORT
Mindy Gore and Lindsey Hutt-Fletcher
Department of Microbiology and Immunology, Louisiana State University Health Sciences Center, USA
Posterabstract:
Ten glycoproteins are currently said to be present in the envelope of EBV. However, in silico analysis
suggests that there may in fact be eleven. The BDLF2 gene, which proteomic analysis has identified as a
tegument protein, is instead predicted to encode a type II membrane protein with six potential N-linked
glycosylation sites in its carboxyterminal ectodomain. In the related murine gammaherpesvirus 68, the
homolog of BDLF2, ORF27 or gp48, interacts with a second glycoprotein, ORF58, a homolog of EBV
BMRF2. To characterize the BDLF2 gene product further, antibody was made to GST-fusions of both the
aminoterminal and carboxyterminal domains of BDLF2 and the loop of BMRF2 which contains an RGD
motif. BDLF2 and BMRF2 were also cloned for expression in mammalian cells. Indirect
immunofluorescence staining demonstrated a globular accumulation of protein in cells expressing BDLF2
alone, but in cells expressing both BDLF2 and BMRF2 the BDLF2 protein relocalized to a smooth rim at
the plasma membrane. Western blotting revealed that when expressed alone BDLF2 is a protein of 68 kDa
and can be digested with endoglycosidase H to 46 kDa, the predicted size of the protein backbone.
However, when expressed together with BMRF2, BDLF2 carries endoglycosidase H resistant sugars. In
addition to full-length BDLF2, both amino- and carboxyterminal fragments are found in purified EBV
virions. These are of a size consistent with cleavage at a potential furin or related proprotein convertase
site. Antibody to BMRF2 is able to immunoprecipitate full length BDLF2 and the aminoterminal, but not
the carboxyterminal cleavage product. Together these data suggest that BDLF2 is an eleventh glycosylated
virion envelope protein that complexes with and is dependent on BMRF2 for processing and transport.
The carboxyterminal cleavage product of BDLF2, however, may interact with additional viral or cellular
proteins.
EBV Conference 2008 Guangzhou
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