title: Embryonic expression of endogenous retroviral RNAs in somatic tissues adjacent to the Oikopleura germline.
abstract: Selective pressure to maintain small genome size implies control of transposable elements, and most old classes of retrotransposons are indeed absent from the very compact genome of the tunicate Oikopleura dioica. Nonetheless, two families of retrotransposons are present, including the Tor elements. The gene organization within Tor elements is similar to that of LTR retrotransposons and retroviruses. In addition to gag and pol, many Tor elements carry a third gene encoding viral envelope-like proteins (Env) that may mediate infection. We show that the Tor family contains distinct classes of elements. In some classes, env mRNA is transcribed from the 5'LTR as in retroviruses. In others, env is transcribed from an additional promoter located downstream of the 5'LTR. Tor Env proteins are membrane-associated glycoproteins which exhibit some features of viral membrane fusion proteins. Whereas some elements are expressed in the adult testis, many others are specifically expressed in embryonic somatic cells adjacent to primordial germ cells. Such embryonic expression depends on determinants present in the Tor elements and not on their surrounding genomic environment. Our study shows that unusual modes of transcription and expression close to the germline may contribute to the proliferation of Tor elements.
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway simon.henriet@sars.uib.no.
authors.forename: Simon
authors.initials: S
authors.lastname: Henriet
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway.
authors.forename: Sara
authors.initials: S
authors.lastname: Sumic
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway.
authors.forename: Carlette
authors.initials: C
authors.lastname: Doufoundou-Guilengui
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway.
authors.forename: Marit Flo
authors.initials: MF
authors.lastname: Jensen
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway.
authors.forename: Camille
authors.initials: C
authors.lastname: Grandmougin
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway.
authors.forename: Kateryna
authors.initials: K
authors.lastname: Fal
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway Department of Biology, University of Bergen, Bergen, N-5020, Norway.
authors.forename: Eric
authors.initials: E
authors.lastname: Thompson
authors.affiliation: Institut de Génomique Fonctionnelle de Lyon, Ecole Normale Supérieure de Lyon - CNRS UMR 5242 - INRA USC 1370, Lyon, 69364 Lyon cedex 07, France.
authors.forename: Jean-Nicolas
authors.initials: JN
authors.lastname: Volff
authors.affiliation: Sars International Centre for Marine Molecular Biology, University of Bergen, Bergen, N-5008, Norway.
authors.forename: Daniel
authors.initials: D
authors.lastname: Chourrout
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D020077:Endogenous Retroviruses / Q000235:genetics*; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells; D057809:HEK293 Cells; D006801:Humans; D008969:Molecular Sequence Data; D011110:Polymorphism, Genetic; D011401:Promoter Regions, Genetic; D012313:RNA / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D014561:Urochordata / Q000235:genetics*; D014759:Viral Envelope Proteins / Q000737:chemistry
chemical_list: D014759:Viral Envelope Proteins; D012313:RNA