Highlights d The Nxf3 pathway: nuclear export for heterochromatic piRNA precursors in Drosophila d Nxf3 obtains chromatin-mediated RNA cargo specificity through the Bootlegger protein d The Nxf3 pathway mediates retrovirus-like evasion of nuclear RNA surveillance d Nxf3-Bootlegger deliver piRNA precursors to cytoplasmic processing granules

Interactive data links: High-throughput sequencing (UCSC browser session); Mass spectrometry (interactive plots) PIWI-interacting RNAs (piRNAs) guide transposon silencing in animals. The 22-30nt piRNAs are processed in the cytoplasm from long non-coding RNAs. How piRNA precursors, which often lack RNA processing hallmarks of export-competent transcripts, achieve nuclear export is unknown. Here, we uncover the RNA export pathway specific for piRNA precursors in the Drosophila germline. This pathway requires Nxf3-Nxt1, a variant of the hetero-dimeric mRNA export receptor Nxf1-Nxt1. Nxf3 interacts with UAP56, a nuclear RNA helicase essential for mRNA export, and CG13741/Bootlegger, which recruits Nxf3-Nxt1 and UAP56 to heterochromatic piRNA source loci. Upon RNA cargo binding, Nxf3 achieves nuclear export via the exportin Crm1, and accumulates together with Bootlegger in perinuclear nuage, suggesting that after export, Nxf3-Bootlegger delivers precursor transcripts to the piRNA processing sites. Our findings indicate that the piRNA pathway bypasses nuclear RNA surveillance systems to achieve export of heterochromatic, unprocessed transcripts to the cytoplasm, a strategy also exploited by retroviruses.

For many years, GIS has been a flexible tool for a wide range of spatial tasks in the spatial planning curriculum of at TU Wien. The steadily increasing number of students, the rising number of participants struggling with solving analytical problems, as well as suboptimal evaluation strategies initiated a total redesign of the course. We have rebuilt the didactic concept to better support the learning process and strengthen the understanding of learned skills, and have automated large parts of the evaluation, which allows for a more thorough assessment of quantitative results.