title: Mechanism of the piRNA-mediated silencing of Drosophila telomeric retrotransposons.
abstract: In the Drosophila germline, retrotransposons are silenced by the PIWI-interacting RNA (piRNA) pathway. Telomeric retroelements HeT-A, TART and TAHRE, which are involved in telomere maintenance in Drosophila, are also the targets of piRNA-mediated silencing. We have demonstrated that expression of reporter genes driven by the HeT-A promoter is under the control of the piRNA silencing pathway independent of the transgene location. In order to test directly whether piRNAs affect the transcriptional state of retrotransposons we performed a nuclear run-on (NRO) assay and revealed increased density of the active RNA polymerase complexes at the sequences of endogenous HeT-A and TART telomeric retroelements as well as HeT-A-containing constructs in the ovaries of spn-E mutants and in flies with piwi knockdown. This strongly correlates with enrichment of two histone H3 modifications (dimethylation of lysine 79 and dimethylation of lysine 4), which mark transcriptionally active chromatin, on the same sequences in the piRNA pathway mutants. spn-E mutation and piwi knockdown results in transcriptional activation of some other non-telomeric retrotransposons in the ovaries, such as I-element and HMS Beagle. Therefore piRNA-mediated transcriptional mode of silencing is involved in the control of retrotransposon expression in the Drosophila germline.
authors.affiliation: Institute of Molecular Genetics, Russian Academy of Sciences, Moscow, Russia.
authors.forename: Sergey
authors.initials: S
authors.lastname: Shpiz
authors.forename: Ivan
authors.initials: I
authors.lastname: Olovnikov
authors.forename: Anna
authors.initials: A
authors.lastname: Sergeeva
authors.forename: Sergey
authors.initials: S
authors.lastname: Lavrov
authors.forename: Yuri
authors.initials: Y
authors.lastname: Abramov
authors.forename: Mikhail
authors.initials: M
authors.lastname: Savitsky
authors.forename: Alla
authors.initials: A
authors.lastname: Kalmykova
mesh_terms: D000818:Animals; D004330:Drosophila / Q000235:genetics*; D005260:Female; D020868:Gene Silencing; D017930:Genes, Reporter; D009154:Mutation; D010053:Ovary / Q000378:metabolism; D034741:RNA, Small Interfering / Q000378:metabolism*; D018626:Retroelements; D016615:Telomere / Q000235:genetics*; D014158:Transcription, Genetic; D015854:Up-Regulation
chemical_list: D034741:RNA, Small Interfering; D018626:Retroelements