Hierarchical roles of mitochondrial Papi and Zucchini in Bombyx germline piRNA biogenesis.

摘要: PIWI-interacting RNAs (piRNAs) are small regulatory that bind to PIWI proteins control transposons and maintain genome integrity in animal germ lines. piRNA 3' end formation the silkworm Bombyx mori has been shown be mediated by 3'-to-5' exonuclease Trimmer (Trim; known as PNLDC1 mammals), intermediates bound with anchored onto mitochondrial Tudor domain protein Papi. However, it remains unclear whether Zucchini (Zuc) endonuclease Nibbler (Nbr) exonuclease, both of which have pivotal roles biogenesis Drosophila, required for processing other species. Here we show loss Zuc had no effect on levels Trim Nbr, but resulted aberrant accumulation within Papi complex, these were processed form mature piRNAs recombinant Zuc. exerted its RNA-binding activity only when phosphorylated, suggesting complex assembly involves a hierarchical process. Both 5' ends showed hallmarks 'slicer' activity, yet phasing pattern was observed piRNAs. The did not affect 5'- 3'-end intermediates, strongly supporting idea is formed slicer independently Zuc, whereas endonuclease. machinery simpler than because transcriptional silencing relies phased