title: A CRE/AP-1-like motif is essential for induced syncytin-2 expression and fusion in human trophoblast-like model.
abstract: Syncytin-2 is encoded by the envelope gene of Endogenous Retrovirus-FRD (ERVFRD-1) and plays a critical role in fusion of placental trophoblasts leading to the formation of the multinucleated syncytiotrophoblast. Its expression is consequently regulated in a strict manner. In the present study, we have identified a forskolin-responsive region located between positions -300 to -150 in the Syncytin-2 promoter region. This 150 bp region in the context of a minimal promoter mediated an 80-fold induction of promoter activity following forskolin stimulation. EMSA analyses with competition experiments with nuclear extracts from forskolin-stimulated BeWo cells demonstrated that the -211 to -177 region specifically bound two forskolin-induced complexes, one of them containing a CRE/AP-1-like motif. Site-directed mutagenesis of the CRE/AP-1 binding site in the context of the Syncytin-2 promoter or a heterologous promoter showed that this motif was mostly essential for forskolin-induced promoter activity. Transfection experiments with dominant negative mutants and constitutively activated CREB expression vectors in addition to Chromatin Immunoprecipitation suggested that a CREB family member, CREB2 was binding and acting through the CRE/AP-1 motif. We further demonstrated the binding of JunD to this same motif. Similar to forskolin and soluble cAMP, CREB2 and JunD overexpression induced Syncytin-2 promoter activity in a CRE/AP-1-dependent manner and Syncytin-2 expression. In addition, BeWo cell fusion was induced by both CREB2 and JunD overexpression, while being repressed following silencing of either gene. These results thereby demonstrate that induced expression of Syncytin-2 is highly dependent on the interaction of bZIP-containing transcription factors to a CRE/AP-1 motif and that this element is important for the regulation of Syncytin-2 expression, which results in the formation of the peripheral syncytiotrophoblast layer.
authors.affiliation: Département des Sciences Biologiques and Centre de recherche BioMed, Université du Québec à Montréal, Montréal, Canada.
authors.forename: Chirine
authors.initials: C
authors.lastname: Toufaily
authors.affiliation: Département des Sciences Biologiques and Centre de recherche BioMed, Université du Québec à Montréal, Montréal, Canada.
authors.forename: Adjimon Gatien
authors.initials: AG
authors.lastname: Lokossou
authors.affiliation: Département des Sciences Biologiques and Centre de recherche BioMed, Université du Québec à Montréal, Montréal, Canada.
authors.forename: Amandine
authors.initials: A
authors.lastname: Vargas
authors.affiliation: Département des Sciences Biologiques and Centre de recherche BioMed, Université du Québec à Montréal, Montréal, Canada.
authors.forename: Éric
authors.initials: É
authors.lastname: Rassart
authors.affiliation: Département des Sciences Biologiques and Centre de recherche BioMed, Université du Québec à Montréal, Montréal, Canada.
authors.forename: Benoit
authors.initials: B
authors.lastname: Barbeau
mesh_terms: D000328:Adult; D002459:Cell Fusion; D045744:Cell Line, Tumor; D005260:Female; D005786:Gene Expression Regulation / Q000502:physiology*; D006801:Humans; D008954:Models, Biological; D059372:Nucleotide Motifs / Q000502:physiology*; D011257:Pregnancy Proteins / Q000096:biosynthesis* / Q000235:genetics; D016755:Proto-Oncogene Proteins c-jun / Q000235:genetics / Q000378:metabolism; D020218:Response Elements / Q000502:physiology*; D014327:Trophoblasts / Q000166:cytology / Q000378:metabolism*
chemical_list: C518353:ERVFRD-1 protein, human; C559371:JunD protein, human; D011257:Pregnancy Proteins; D016755:Proto-Oncogene Proteins c-jun