title: The LTR enhancer of ERV-9 human endogenous retrovirus is active in oocytes and progenitor cells in transgenic zebrafish and humans.
abstract: The solitary LTRs of ERV-9 human endogenous retrovirus are middle repetitive DNAs associated with 3,000-4,000 human gene loci including the beta-globin gene locus where the ERV-9 LTR is juxtaposed to the locus control region (beta-LCR) far upstream of the globin genes. The ERV-9 LTRs are conserved during primate evolution, but their function in the primate genomes is unknown. Here, we show that in transgenic zebrafish harboring the beta-globin ERV-9 LTR coupled to the GFP gene, the LTR enhancer was active and initiated synthesis of GFP mRNA in oocytes but not in spermatozoa, and GFP expression in the embryos was maternally inherited. The LTR enhancer was active also in stem/progenitor cell regions of adult tissues of transgenic zebrafish. In human tissues, ERV-9 LTR enhancer was active also in oocytes and stem/progenitor cells but not in spermatozoa and a number of differentiated, adult somatic cells. Transcriptional analyses of the human beta-globin gene locus showed that the beta-globin ERV-9 LTR enhancer initiated RNA synthesis from the LTR in the direction of the downstream beta locus control region and globin genes in ovary and erythroid progenitor cells. The findings suggest that, during oogenesis, ERV-9 LTR enhancers in the human genome could activate the cis-linked gene loci to synthesize maternal mRNAs required for early embryogenesis. Alternatively, the ERV-9 LTR enhancers, in initiating RNA syntheses into the downstream genomic DNAs, could transcriptionally potentiate and preset chromatin structure of the cis-linked gene loci in oocytes and adult stem/progenitor cells.
authors.affiliation: Department of Biochemistry and Molecular Biology and Institute of Molecular Medicine and Genetics, Medical College of Georgia, Augusta, GA 30912, USA.
authors.forename: Wenhu
authors.initials: W
authors.lastname: Pi
authors.forename: Zhongan
authors.initials: Z
authors.lastname: Yang
authors.forename: Jian
authors.initials: J
authors.lastname: Wang
authors.forename: Ling
authors.initials: L
authors.lastname: Ruan
authors.forename: Xiuping
authors.initials: X
authors.lastname: Yu
authors.forename: Jianhua
authors.initials: J
authors.lastname: Ling
authors.forename: Sanford
authors.initials: S
authors.lastname: Krantz
authors.forename: Carlos
authors.initials: C
authors.lastname: Isales
authors.forename: Simon J
authors.initials: SJ
authors.lastname: Conway
authors.forename: Shuo
authors.initials: S
authors.lastname: Lin
authors.forename: Dorothy
authors.initials: D
authors.lastname: Tuan
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D002454:Cell Differentiation; D020077:Endogenous Retroviruses / Q000235:genetics*; D004742:Enhancer Elements, Genetic; D005260:Female; D005914:Globins / Q000235:genetics; D049452:Green Fluorescent Proteins; D006801:Humans; D019901:Locus Control Region; D008164:Luminescent Proteins / Q000235:genetics; D008297:Male; D009865:Oocytes / Q000378:metabolism / Q000821:virology*; D009866:Oogenesis / Q000235:genetics; D011994:Recombinant Proteins / Q000235:genetics; D013094:Spermatozoa / Q000821:virology; D013234:Stem Cells / Q000378:metabolism / Q000821:virology*; D020079:Terminal Repeat Sequences; D015027:Zebrafish
chemical_list: D008164:Luminescent Proteins; D011994:Recombinant Proteins; D049452:Green Fluorescent Proteins; D005914:Globins