A Heterochromatin-Specific RNA Export Pathway Facilitates piRNA Production.

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.
Mesh Terms:
Active Transport, Cell Nucleus, Animals, Animals, Genetically Modified, Argonaute Proteins, Cell Line, Cell Nucleus, Cytoplasm, DEAD-box RNA Helicases, DNA Transposable Elements, Drosophila Proteins, Drosophila melanogaster, Gene Silencing, Germ Cells, Heterochromatin, Intracellular Signaling Peptides and Proteins, Karyopherins, Nucleocytoplasmic Transport Proteins, RNA, Small Interfering, RNA-Binding Proteins, Receptors, Cytoplasmic and Nuclear, Transcription, Genetic
Cell
Date: Dec. 08, 2018
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