Project description:PIWI-clade Argonaute proteins repress transposable elements in animal gonads. Their sequence specificity is conferred via bound ~23-30nt long piRNAs, which are processed from single stranded precursor RNAs. How transcripts are specified as precursors and processed into stereotypical piRNA populations are central unresolved questions. Here we show that piRNA-guided RNA cleavage in Drosophila results not only in generation of a ping-pong partner piRNA but further triggers efficient 3′ directed and phased primary piRNA biogenesis. Phasing is a feature of primary piRNAs in somatic and germline cells and a consequence of consecutive endo-nucleolytic cleavage events catalyzed by Zucchini. Formation of 3′ and 5′ ends of flanking piRNAs is therefore tightly coupled. Zucchini also participates in 3′ end formation of secondary piRNAs but its function can be bypassed by additional downstream piRNA-guided cleavages and subsequent precursor trimming. Hallmarks of Zucchini-dependent phased piRNA biogenesis are also evident in mouse testes, pointing to an evolutionarily conserved mechanism of piRNA biogenesis.
Project description:PIWI-clade Argonaute proteins repress transposable elements in animal gonads. Their sequence specificity is conferred via bound ~23-30nt long piRNAs, which are processed from single stranded precursor RNAs. How transcripts are specified as precursors and processed into stereotypical piRNA populations are central unresolved questions. Here we show that piRNA-guided RNA cleavage in Drosophila results not only in generation of a ping-pong partner piRNA but further triggers efficient 3′ directed and phased primary piRNA biogenesis. Phasing is a feature of primary piRNAs in somatic and germline cells and a consequence of consecutive endo-nucleolytic cleavage events catalyzed by Zucchini. Formation of 3′ and 5′ ends of flanking piRNAs is therefore tightly coupled. Zucchini also participates in 3′ end formation of secondary piRNAs but its function can be bypassed by additional downstream piRNA-guided cleavages and subsequent precursor trimming. Hallmarks of Zucchini-dependent phased piRNA biogenesis are also evident in mouse testes, pointing to an evolutionarily conserved mechanism of piRNA biogenesis. This study aims at understanding how piRNA biogenesis is intiated in the Drosophila germline and understanding the role of the nuclease Zucchini/MitoPLD in piRNA biogenesis in Drosophila/Mouse by analysing small RNA sequencing data of various genotypes and sensor constructs.
Project description:PIWI proteins and their bound piRNAs form the core of a gonad specific small RNA silencing pathway in animals that protects the genome against the deleterious activity of transposable elements. Recent studies linked the piRNA pathway to TUDOR biology, where TUDOR domains of various proteins recognize and bind symmetrically methylated Arginine residues in PIWI proteins. We systematically analyzed the Drosophila TUDOR protein family and identified three previously not characterized TUDOR domain-containing genes (CG4771, CG14303 and CG11133) as essential piRNA pathway members. We characterized CG4771 (Avocado) in detail and demonstrate a critical role for this protein during primary piRNA biogenesis in somatic and germline cells of the ovary. Avocado physically and/or genetically interacts with the primary pathway components Piwi, Armitage, Yb and Zucchini. Avocado also interacts with the Tdrd12 orthologs CG11133 and CG31755, which are essential for primary piRNA biogenesis in the germline and probably functionally replace the related and soma specific factor Yb.
Project description:PIWI proteins and their bound piRNAs form the core of a gonad specific small RNA silencing pathway in animals that protects the genome against the deleterious activity of transposable elements. Recent studies linked the piRNA pathway to TUDOR biology, where TUDOR domains of various proteins recognize and bind symmetrically methylated Arginine residues in PIWI proteins. We systematically analyzed the Drosophila TUDOR protein family and identified three previously not characterized TUDOR domain-containing genes (CG4771, CG14303 and CG11133) as essential piRNA pathway members. We characterized CG4771 (Avocado) in detail and demonstrate a critical role for this protein during primary piRNA biogenesis in somatic and germline cells of the ovary. Avocado physically and/or genetically interacts with the primary pathway components Piwi, Armitage, Yb and Zucchini. Avocado also interacts with the Tdrd12 orthologs CG11133 and CG31755, which are essential for primary piRNA biogenesis in the germline and probably functionally replace the related and soma specific factor Yb. small RNA libraries were prepared from total RNA isolation of 8 different genotypes