Dataset Information

Panoramix enforces piRNA-dependent cotranscriptional silencing.

ABSTRACT: The Piwi-interacting RNA (piRNA) pathway is a small RNA-based innate immune system that defends germ cell genomes against transposons. In Drosophila ovaries, the nuclear Piwi protein is required for transcriptional silencing of transposons, though the precise mechanisms by which this occurs are unknown. Here we show that the CG9754 protein is a component of Piwi complexes that functions downstream of Piwi and its binding partner, Asterix, in transcriptional silencing. Enforced tethering of CG9754 to nascent messenger RNA transcripts causes cotranscriptional silencing of the source locus and the deposition of repressive chromatin marks. We have named CG9754 "Panoramix," and we propose that this protein could act as an adaptor, scaffolding interactions between the piRNA pathway and the general silencing machinery that it recruits to enforce transcriptional repression.

SUBMITTER: Yu Y

PROVIDER: S-EPMC4722808 | biostudies-literature | 2015 Oct

REPOSITORIES: biostudies-literature

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Panoramix enforces piRNA-dependent cotranscriptional silencing.

Yu Yang Y Gu Jiaqi J Jin Ying Y Luo Yicheng Y Preall Jonathan B JB Ma Jinbiao J Czech Benjamin B Hannon Gregory J GJ

Science (New York, N.Y.) 20151001 6258

The Piwi-interacting RNA (piRNA) pathway is a small RNA-based innate immune system that defends germ cell genomes against transposons. In Drosophila ovaries, the nuclear Piwi protein is required for transcriptional silencing of transposons, though the precise mechanisms by which this occurs are unknown. Here we show that the CG9754 protein is a component of Piwi complexes that functions downstream of Piwi and its binding partner, Asterix, in transcriptional silencing. Enforced tethering of CG975 ...[more]

PMID: 26472911

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Project description:PIWI-clade Argonaute proteins silence transposon expression in animal gonads. Their target specificity is defined by bound ~23-30nt piRNAs that are processed from single-stranded precursor transcripts via two distinct pathways. Primary piRNAs are defined by the endo-nuclease Zucchini, while biogenesis of secondary piRNAs depends on piRNA-guided transcript cleavage and results in piRNA amplification. Here, we analyze the inter-dependencies between these piRNA biogenesis pathways in the developing Drosophila ovary. We show that secondary piRNA-guided target slicing is the predominant mechanism that specifies transcripts—including those from piRNA clusters—as primary piRNA precursors and that defines the spectrum of Piwi-bound piRNAs in germline cells. Post-transcriptional silencing in the cytoplasm therefore enforces nuclear, transcriptional target silencing, which ensures the tight suppression of transposons during oogenesis. As target slicing also defines the nuclear piRNA pool during mouse spermatogenesis, our findings uncover an unexpected conceptual similarity between the mouse and fly piRNA pathways. To understand the hierarchical order of primary versus secondary piRNA biogenesis in Drosophila ovaries, we sequenced piRNAs bound to total-Piwi, germline-Piwi, Aubergine and Argonaute3 from ovaries of germline specific knockdowns of control, piwi, aub, ago3 single knockdowns and aub/ago3 double knockdowns. To determine changes in Transposable Element (TE) transcription or TE RNA steady state in perturbed piRNA pathway conditions, we performed Pol2-ChIP-sequencing and polyA bound RNA-sequencing from ovaries of multiple germline knockdown genotypes. We also sequenced genomic DNA from ovaries of control knockdowns to experimentally estimate the TE copy number in our genetic background. Finally, we used CAP-seq from germline specific Piwi depletions to identify the Transcriptional Start Sites (TSS) in TEs in a deregulated background. Replicates are labeled with R1, R2, R3, R4 where indicated.

Dataset Information

Panoramix enforces piRNA-dependent cotranscriptional silencing.

Publications

Panoramix enforces piRNA-dependent cotranscriptional silencing.

Similar Datasets

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