Mechanism of the piRNA-mediated silencing of Drosophila telomeric retrotransposons
نویسندگان
چکیده
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.
منابع مشابه
Role of piRNAs in the Drosophila telomere homeostasis
Drosophila telomeres are maintained as a result of transpositions of specialized telomeric retrotransposons. The abundance of telomeric retroelement transcripts, as well as the frequency of their transpositions onto the chromosome ends, is controlled by a PIWI-interacting RNA (piRNA) pathway. In our recent report, we demonstrate strong evidence of piRNA-mediated transcriptional silencing of tel...
متن کاملrasiRNA pathway controls antisense expression of Drosophila telomeric retrotransposons in the nucleus
Telomeres in Drosophila are maintained by the specialized telomeric retrotransposons HeT-A, TART and TAHRE. Sense transcripts of telomeric retroelements were shown to be the targets of a specialized RNA-interference mechanism, a repeat-associated short interfering (rasi)RNA-mediated system. Antisense rasiRNAs play a key role in this mechanism, highlighting the importance of antisense expression...
متن کاملGene silencing mechanisms mediated by Aubergine piRNA complexes in Drosophila male gonad.
Genetic studies have shown that Aubergine (Aub), one of the Piwi subfamily of Argonautes in Drosophila, is essential for germ cell formation and maintaining fertility. aub mutations lead to the accumulation of retrotransposons in ovaries and testes, and Stellate transcripts in testes. Aub in ovaries associates with a variety of Piwi-interacting RNAs (piRNAs) derived from repetitive intergenic e...
متن کاملHeT-A_pi1, a piRNA Target Sequence in the Drosophila Telomeric Retrotransposon HeT-A, Is Extremely Conserved across Copies and Species
The maintenance of the telomeres in Drosophila species depends on the transposition of the non-LTR retrotransposons HeT-A, TAHRE and TART. HeT-A and TART elements have been found in all studied species of Drosophila suggesting that their function has been maintained for more than 60 million years. Of the three elements, HeT-A is by far the main component of D. melanogaster telomeres and, unexpe...
متن کاملSpatio-temporal requirements for transposable element piRNA-mediated silencing during Drosophila oogenesis
During Drosophila oogenesis, transposable element (TE) repression involves the Piwi-interacting RNA (piRNA) pathway which ensures genome integrity for the next generation. We developed a transgenic model to study repression of the Idefix retrotransposon in the germline. Using a candidate gene KD-approach, we identified differences in the spatio-temporal requirements of the piRNA pathway compone...
متن کامل