A multipotential β-1,6- N -acetylglucosaminyl-transferase is encoded by bovine herpesvirus type 4

A multipotential β-1,6-N-acetylglucosaminyl-transferase is encoded by bovine herpesvirus type 4

Departments of ^*Immunology-Vaccinology (B43 bis), ^‖Physiology (B42), and ^§Virology (B43 bis), Faculty of Veterinary Medicine, University of Liège, B-4000 Liège, Belgium; ^**Faculté Universitaire des Sciences Agronomiques, 13 avenue Maréchal Juin, B-5030 Gembloux, Belgium; and ^¶Burnham Institute, 10901 North Torrey Pines Road, La Jolla, CA 92037

Edited by Stuart A. Kornfeld, Washington University School of Medicine, St. Louis, MO, and approved March 15, 2000 (received for review February 9, 2000)

Abstract

The β-1,6-N-acetylglucosaminyltransferase (β1,6GnT) gene family encodes enzymes playing crucial roles in glycan synthesis. Important changes in β1,6GnT expression are observed during development, oncogenesis, and immunodeficiency. The most characterized β1,6GnTs in this gene family are the human (h) C2GnT-L and h-IGnT, which have core 2 [Galβ1→3(GlcNAcβ1→6)GalNAc] and I branching [GlcNAcβ1→3(GlcNAcβ1→6)Gal] activities, respectively. Recently, h-C2GnT-M was shown to be unique in forming core 2, core 4 [GlcNAcβ1→3(GlcNAcβ1→6)GalNAc], and I structures. To date, the β1,6GnT gene family has been characterized only in mammals. Here, we describe that bovine herpesvirus type 4 (BHV-4) encodes a β1,6GnT expressed during viral replication and exhibiting all of the core 2, core 4, and I branching activities. Sequencing of the BHV-4 genome revealed an ORF, hereafter called BORFF3–4, encoding a protein (pBORFF3–4) exhibiting 81.1%, 50.7%, and 36.6% amino acid identity with h-C2GnT-M, h-C2GnT-L, and h-IGnT, respectively. Reverse transcriptase-PCR analysis revealed that BORFF3–4 is expressed during BHV-4 replication. Expression of BORFF3–4 in Chinese hamster ovary cells directed the expression of core 2 branched oligosaccharides and I antigenic structures on the cell surface. Moreover, a soluble form of pBORFF3–4 had core 4 branching activity in addition to core 2 and I branching activities. Finally, infection of a C2GnT-negative cell line with BHV-4 induced expression of core 2 branched oligosaccharides. This study extends the β1,6GnT gene family to a viral gene and provides a model to study the biological functions of a β1,6GnT in the context of viral infection.

Footnotes

↵ † A.V. and N. M.-G. contributed equally to this work.
↵ ‡ To whom reprint requests should be sent at the * address. E-mail: A.vdplasschen{at}ulg.ac.be.
This paper was submitted directly (Track II) to the PNAS office.
Data deposition: The sequence reported in this paper has been deposited in the GenBank database (accession no. AF231105).
Article published online before print: Proc. Natl. Acad. Sci. USA, 10.1073/pnas.100058897.
Article and publication date are at www.pnas.org/cgi/doi/10.1073/pnas.100058897
Abbreviations:

β1,6GnT,

β-1,6-N-acetylglucosaminyltransferase;

BHV-4,

bovine herpesvirus type 4;

BORFF3–4,

bovine ORF F3–4;

pBORFF3–4,

protein encoded by BORFF3–4;

C2GnT,

C4GnT, and IGnT, core 2, core 4, and I branching β1,6GnT, respectively;

cIGnT,

centrally acting IGnT;

dIGnT,

predistally acting IGnT;

h-C2GnT-L and -M,

human core 2 leukocyte-type β1,6GnT and mucin-type, respectively;

prDNA,

polyrepetitive DNA;

CHO,

Chinese hamster ovary;

EBTr,

embryonic bovine trachea;

α-,

anti-;

RT,

reverse transcriptase