title: Synthesis, assembly, and processing of the Env ERVWE1/syncytin human endogenous retroviral envelope.
abstract: Syncytin is a fusogenic protein involved in the formation of the placental syncytiotrophoblast layer. This protein is encoded by the envelope gene of the ERVWE1 proviral locus belonging to the human endogenous retrovirus W (HERV-W) family. The HERV-W infectious ancestor entered the primate lineage 25 to 40 million years ago. Although the syncytin fusion property has been clearly demonstrated, little is known about this cellular protein maturation process with respect to classical infectious retrovirus envelope proteins. Here we show that the cellular syncytin protein is synthesized as a glycosylated gPr73 precursor cleaved into two mature proteins, a gp50 surface subunit (SU) and a gp24 transmembrane subunit (TM). These SU and TM subunits are found associated as homotrimers. The intracytoplasmic tail is critical to the fusogenic phenotype, although its cleavage requirements seem to have diverged from those of classical retroviral maturation.
authors.affiliation: Laboratoire de Vectorologie Rétrovirale et Thérapie Génique, INSERM U412, Ecole Normale Supérieure de Lyon, 69364 Lyon, France.
authors.forename: V
authors.initials: V
authors.lastname: Cheynet
authors.forename: A
authors.initials: A
authors.lastname: Ruggieri
authors.forename: G
authors.initials: G
authors.lastname: Oriol
authors.forename: J-L
authors.initials: JL
authors.lastname: Blond
authors.forename: B
authors.initials: B
authors.lastname: Boson
authors.forename: L
authors.initials: L
authors.lastname: Vachot
authors.forename: B
authors.initials: B
authors.lastname: Verrier
authors.forename: F-L
authors.initials: FL
authors.lastname: Cosset
authors.forename: F
authors.initials: F
authors.lastname: Mallet
mesh_terms: D000595:Amino Acid Sequence; D002460:Cell Line; D020077:Endogenous Retroviruses / Q000378:metabolism*; D015686:Gene Products, env / Q000096:biosynthesis*; D006031:Glycosylation; D006801:Humans; D008969:Molecular Sequence Data; D011257:Pregnancy Proteins / Q000096:biosynthesis*; D011498:Protein Precursors / Q000378:metabolism; D021122:Protein Subunits / Q000235:genetics; D043562:Receptors, G-Protein-Coupled / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment
chemical_list: D015686:Gene Products, env; C470837:PROKR1 protein, human; D011257:Pregnancy Proteins; D011498:Protein Precursors; D021122:Protein Subunits; D043562:Receptors, G-Protein-Coupled; C405335:syncytin