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J. Virol., 05 1996, 3032-3038, Vol 70, No. 5
GM Keil, T Engelhardt, A Karger and M Enz
Sequence analysis of the short unique (Us) segment of the bovine
herpesvirus 1 (BHV-1) genome predicted that the Us open reading frame (ORF)
4 encodes a protein with homology to glycoprotein G (gG) of other
alpha-herpesviruses (P. Leung-Tack, J.-C. Audonnet, and M. Riviere,
Virology 199:409-421, 1994). RNA analysis showed that the Us ORF4 is
contained within two transcripts of 3.5 and 1.8 kb. The 3.5 kb RNA
represents a structurally bicistronic RNA which encompasses the Us ORF3 and
Us ORF4, whereas the 1.8-kb RNA constitutes the monocistronic Us ORF4 mRNA.
To identify the predicted BHV-I gG, recombinant vaccinia virus expressing
the Us ORF4 was used to raise specific antibodies in rabbits. The antiserum
recognized a 65-kDa polypeptide and a very diffusely migrating species of
proteins with an apparent molecular mass of between 90 and greater than 240
kDa in supernatants of BHV-1- infected cells which was also precipitated
together with 61- and 70-kDa polypeptides from cell-associated proteins.
The specificity of the reaction was demonstrated by the absence of these
proteins from the supernatant of cells infected with the Us ORF4 deletion
mutant BHV- l/gp1-8. Treatment of the immunoprecipitated proteins with
glycosidases and chondroitinase AC showed that the 65-kDa protein
constitutes gG, which contains both N- and O-linked carbohydrates, and that
the high- molecular-mass proteins contain glycosaminoglycans linked to a
65-kDa glycoprotein that is antigenically related to gG. These molecules
were therefore named glycoproteoglycan C (gpgG). Pulse chase experiments
indicated that gG and gpgG were processed from a common precursor molecule
with an apparent molecular mass of 61 kDa via a 70-kDa intermediate. Both
gG and gpgG could not be found associated with purified virions. In
summary, our results identify the BHV-I gG protein and demonstrate the
presence of a form of posttranslational modification,
glycosamino-glycosylation, that has not yet been described for a
herpesvirus-encoded protein.
Copyright © 1996, American Society for Microbiology
Bovine herpesvirus 1 U(s) open reading frame 4 encodes a glycoproteoglycan
Institute for Molecular and Cellular Virology, Insel Riems, Germany.
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