PDF, English Restricted access: Repository staff only until 6 February 2026. Login+Download (39MB) | Terms of use

Abstract

The piRNA pathway is found across animals and acts as a defense mechanism to silence transposon activity in germline cells. This ensures the safe transmission of genetic information from one generation to the next. In this pathway, a class of small non-coding RNAs called piRNAs, which have sequences complementary to transposon transcripts, form complexes with PIWI proteins. These piRNAs direct PIWI proteins to transposon transcripts, where the PIWI proteins mediate either transcriptional or post-transcriptional silencing. In addition to PIWI proteins and piRNAs, many other proteins are essential for a functional piRNA pathway, but their molecular and mechanistic functions remain largely unknown. A comprehensive understanding of the molecular interactions among piRNA pathway factors, which is currently scarce, is crucial to elucidate the specific roles of these factors. In this study, I performed a systematic pairwise interaction screen of 22 Drosophila piRNA pathway factors operating in the cytoplasm, including PIWI proteins, RNA helicases and Tudor domain-containing proteins. For this purpose, a novel cell culture-based protein-protein interaction (PPI) assay called ReLo was established. The ReLo screen confirmed all protein complexes previously supported by crystal structures, identified several interactions previously reported by co-IP experiments, and revealed novel complexes. Subsequently, I focused on the structural characterization of two novel protein complexes: Tejas-Krimper and Tejas-Maelstrom, as well as a complex of Armitage with the Gasz-Daed heterodimer. Together, this work significantly advances our understanding of the molecular interaction network underlying the piRNA pathway, provides critical insights into three protein complexes, and is likely to guide future studies to improve our understanding of piRNA biogenesis and function.