Abstract
PIWI-interacting RNAs (piRNAs) guide transposon silencing in animals. The 22–30 nt piRNAs are processed in the cytoplasm from long non-coding RNAs that often lack RNA processing hallmarks of export-competent transcripts. By studying how these transcripts achieve nuclear export, we uncover an 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 peri-nuclear nuage, suggesting that after export, Nxf3-Bootlegger delivers precursor transcripts to the piRNA processing sites. These findings indicate that the piRNA pathway bypasses nuclear RNA surveillance systems to export unprocessed transcripts to the cytoplasm, a strategy also exploited by retroviruses. Heterochromatic piRNA precursors escape classic mRNA quality-control and surveillance mechanisms through a dedicated nuclear export pathway.
Originalsprog | Engelsk |
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Tidsskrift | Cell |
Vol/bind | 178 |
Nummer | 4 |
Sider (fra-til) | 964-979 |
ISSN | 0092-8674 |
DOI | |
Status | Udgivet - 8 aug. 2019 |
Udgivet eksternt | Ja |