title: Epigenetic marking and repression of porcine endogenous retroviruses.
abstract: Endogenous retroviruses (ERVs) are remnants of retroviral germ line infections and have been identified in all mammals investigated so far. Although the majority of ERVs are degenerated, some mammalian species, such as mice and pigs, carry replication-competent ERVs capable of forming infectious viral particles. In mice, ERVs are silenced by DNA methylation and histone modifications and some exogenous retroviruses were shown to be transcriptionally repressed after integration by a primer-binding site (PBS) targeting mechanism. However, epigenetic repression of porcine ERVs (PERVs) has remained largely unexplored so far. In this study, we screened the pig genome for PERVs using LTRharvest, a tool for de novo detection of ERVs, and investigated various aspects of epigenetic repression of three unrelated PERV families. We found that these PERV families are differentially up- or downregulated upon chemical inhibition of DNA methylation and histone deacetylation in cultured porcine cells. Furthermore, chromatin immunoprecipitation analysis revealed repressive histone methylation marks at PERV loci in primary porcine embryonic germ cells and immortalized embryonic kidney cells. PERV elements belonging to the PERV-γ1 family, which is the only known PERV family that has remained active up to the present, were marked by significantly higher levels of histone methylations than PERV-γ2 and PERV-β3 proviruses. Finally, we tested three PERV-associated PBS sequences for repression activity in murine and porcine cells using retroviral transduction experiments and showed that none of these PBS sequences induced immediate transcriptional silencing in the tested primary porcine cells.
authors: Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors: Gernot
authors: G
authors: Wolf
authors: Department of Biomedicine, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors: Anders Lade
authors: AL
authors: Nielsen
authors: Department of Biomedicine, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors: Jacob Giehm
authors: JG
authors: Mikkelsen
authors: Department of Molecular Biology and Genetics, University of Aarhus, DK-8000 Aarhus C, Denmark.
authors: Finn Skou
authors: FS
authors: Pedersen
mesh_terms: D000818:Animals; D001374:Azacitidine / Q000031:analogs & derivatives / Q000494:pharmacology; D002460:Cell Line; D019175:DNA Methylation / Q000187:drug effects; D004279:DNA, Viral / Q000235:genetics; D000077209:Decitabine; D015536:Down-Regulation; D020077:Endogenous Retroviruses / Q000235:genetics* / Q000302:isolation & purification; D004791:Enzyme Inhibitors / Q000494:pharmacology; D063185:Epigenetic Repression; D015967:Gene Expression Regulation, Viral / Q000235:genetics*; D056572:Histone Deacetylase Inhibitors / Q000494:pharmacology; D006657:Histones / Q000187:drug effects; D006877:Hydroxamic Acids / Q000494:pharmacology; D008297:Male; D051379:Mice; D061251:Primary Cell Culture; D011533:Proviruses / Q000235:genetics* / Q000302:isolation & purification; D012333:RNA, Messenger / Q000235:genetics; D012367:RNA, Viral / Q000235:genetics; D013552:Swine; D013553:Swine Diseases / Q000821:virology*; D013556:Swine, Miniature; D015854:Up-Regulation
chemical_list: D004279:DNA, Viral; D004791:Enzyme Inhibitors; D056572:Histone Deacetylase Inhibitors; D006657:Histones; D006877:Hydroxamic Acids; D012333:RNA, Messenger; D012367:RNA, Viral; C012589:trichostatin A; D000077209:Decitabine; D001374:Azacitidine