title: Control of vitellogenin genes expression by sequences derived from transposable elements in rainbow trout.
abstract: In most of oviparous animals, vitellogenins (VTG) are the major egg yolk precursors. They are produced in the liver under the control of estrogens. In rainbow trout (Oncorhynchus mykiss), the vtg genes cluster contains an unusually large number of almost identical gene copies. In order to identify the regulatory elements in their promoters, we used a combination of reporter plasmids containing genomic sequences including putative estrogen response elements (EREs) and we performed transient transfection assays in MCF-7 and yeast cells. We found a functional ERE corresponding to the sequence GGGGCAnnnTAACCT (rtvtgERE), which differs from the consensus ERE (ERE(cs)) by three base pairs. This non-palindromic ERE is located in the env gene of a retrotransposon relic, 180 base pairs upstream of the transcriptional start site. Fluorescence anisotropy experiments confirmed that the purified human estrogen receptor alpha (hERalpha) can specifically bind to rtvtgERE. Furthermore, we observe that the stability of hERalpha-ERE(cs) and hERalpha-rtvtgERE complexes is similar with equilibrium dissociation constants of 3.0nM and 6.2nM respectively, under our experimental conditions. Additionally, this rtvtgERE sequence displays a high E2-responsiveness through ER activation in cellulo. In the rainbow trout, the functional ERE (rtvtgERE) lies within promoter sequences which are mostly composed of sequences derived from transposable elements (TEs), which therefore may have acted as an evolutionary buffer to secure the proper expression of these genes.
authors.affiliation: Laboratoire d'Ingénierie des Matériaux de Bretagne, Université de Bretagne-Sud, CER Yves Coppens, BP573, 56017 Vannes CEDEX, France.
authors.forename: Anthony
authors.initials: A
authors.lastname: Bouter
authors.forename: Nicolas
authors.initials: N
authors.lastname: Buisine
authors.forename: Adélaïde
authors.initials: A
authors.lastname: Le Grand
authors.forename: Nathalie
authors.initials: N
authors.lastname: Mouchel
authors.forename: Franck
authors.initials: F
authors.lastname: Chesnel
authors.forename: Catherine
authors.initials: C
authors.lastname: Le Goff
authors.forename: Véronique
authors.initials: V
authors.lastname: Le Tilly
authors.forename: Jacques
authors.initials: J
authors.lastname: Wolff
authors.forename: Olivier
authors.initials: O
authors.lastname: Sire
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics / Q000378:metabolism; D002478:Cells, Cultured; D004251:DNA Transposable Elements / Q000235:genetics*; D047628:Estrogen Receptor alpha / Q000378:metabolism; D005260:Female; D005786:Gene Expression Regulation; D006801:Humans; D017686:Oncorhynchus mykiss / Q000235:genetics*; D010957:Plasmids; D016133:Polymerase Chain Reaction; D011401:Promoter Regions, Genetic / Q000235:genetics*; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D014819:Vitellogenins / Q000235:genetics* / Q000378:metabolism
chemical_list: D004251:DNA Transposable Elements; D047628:Estrogen Receptor alpha; D014819:Vitellogenins