title: Bovine Herpesvirus 4 Modulates Its β-1,6-N-Acetylglucosaminyltransferase Activity through Alternative Splicing.
abstract: Carbohydrates play major roles in host-virus interactions. It is therefore not surprising that, during coevolution with their hosts, viruses have developed sophisticated mechanisms to hijack for their profit different pathways of glycan synthesis. Thus, the Bo17 gene of Bovine herpesvirus 4 (BoHV-4) encodes a homologue of the cellular core 2 protein β-1,6-N-acetylglucosaminyltransferase-mucin type (C2GnT-M), which is a key player for the synthesis of complex O-glycans. Surprisingly, we show in this study that, as opposed to what is observed for the cellular enzyme, two different mRNAs are encoded by the Bo17 gene of all available BoHV-4 strains. While the first one corresponds to the entire coding sequence of the Bo17 gene, the second results from the splicing of a 138-bp intron encoding critical residues of the enzyme. Antibodies generated against the Bo17 C terminus showed that the two forms of Bo17 are expressed in BoHV-4 infected cells, but enzymatic assays revealed that the spliced form is not active. In order to reveal the function of these two forms, we then generated recombinant strains expressing only the long or the short form of Bo17. Although we did not highlight replication differences between these strains, glycomic analyses and lectin neutralization assays confirmed that the splicing of the Bo17 gene gives the potential to BoHV-4 to fine-tune the global level of core 2 branching activity in the infected cell. Altogether, these results suggest the existence of new mechanisms to regulate the activity of glycosyltransferases from the Golgi apparatus.
  
  
  OBJECTIVE
  Viruses are masters of adaptation that hijack cellular pathways to allow their growth. Glycans play a central role in many biological processes, and several studies have highlighted mechanisms by which viruses can affect glycosylation. Glycan synthesis is a nontemplate process regulated by the availability of key glycosyltransferases. Interestingly, bovine herpesvirus 4 encodes one such enzyme which is a key enzyme for the synthesis of complex O-glycans. In this study, we show that, in contrast to cellular homologues, this virus has evolved to alternatively express two proteins from this gene. While the first one is enzymatically active, the second results from the alternative splicing of the region encoding the catalytic site of the enzyme. We postulate that this regulatory mechanism could allow the virus to modulate the synthesis of some particular glycans for function at the location and/or the moment of infection.
authors.affiliation: Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, FARAH, University of Liège, Liege, Belgium.
authors.forename: Céline
authors.initials: C
authors.lastname: Lété
authors.affiliation: Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, FARAH, University of Liège, Liege, Belgium.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Markine-Goriaynoff
authors.affiliation: Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, FARAH, University of Liège, Liege, Belgium.
authors.forename: Bénédicte
authors.initials: B
authors.lastname: Machiels
authors.affiliation: Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.
authors.forename: Poh-Choo
authors.initials: PC
authors.lastname: Pang
authors.affiliation: Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, FARAH, University of Liège, Liege, Belgium.
authors.forename: Xue
authors.initials: X
authors.lastname: Xiao
authors.affiliation: Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.
authors.forename: Kevin
authors.initials: K
authors.lastname: Canis
authors.affiliation: The Sanford Burnham Medical Research Institute, La Jolla, California, USA.
authors.forename: Masami
authors.initials: M
authors.lastname: Suzuki
authors.affiliation: The Sanford Burnham Medical Research Institute, La Jolla, California, USA.
authors.forename: Minoru
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.
authors.forename: Anne
authors.initials: A
authors.lastname: Dell
authors.affiliation: Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom.
authors.forename: Stuart M
authors.initials: SM
authors.lastname: Haslam
authors.affiliation: Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, FARAH, University of Liège, Liege, Belgium.
authors.forename: Alain
authors.initials: A
authors.lastname: Vanderplasschen
authors.affiliation: Immunology-Vaccinology Laboratory, Department of Infectious and Parasitic Diseases, FARAH, University of Liège, Liege, Belgium L.gillet@ulg.ac.be.
authors.forename: Laurent
authors.initials: L
authors.lastname: Gillet
mesh_terms: D017398:Alternative Splicing; D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D020869:Gene Expression Profiling; D015967:Gene Expression Regulation, Viral; D026021:Herpesvirus 4, Bovine / Q000201:enzymology* / Q000235:genetics*; D017351:N-Acetylglucosaminyltransferases / Q000235:genetics* / Q000378:metabolism*
chemical_list: D017351:N-Acetylglucosaminyltransferases; C037649:N-acetyllactosaminide beta-1,6-N-acetylglucosaminyltransferase