Coupled protein synthesis and ribosome-guided piRNA processing on mRNAs.

Area of Science:

• RNA biology
• Genomics
• Epigenetics

Background:

• PIWI-interacting RNAs (piRNAs) are crucial for germline genome protection and fertility.
• piRNAs are known to originate from transposable element (TE) RNAs and long non-coding RNAs.
• The biogenesis of piRNAs from 3´ untranslated regions (3´UTRs) of protein-coding genes is less understood.

Purpose of the Study:

• To investigate the precursors and biogenesis mechanism of 3´UTR piRNAs.
• To elucidate the role of 3´UTR piRNAs in regulating gene expression and genome stability.
• To explore the conservation of 3´UTR piRNA production in different species.

Main Methods:

• Analysis of mRNA precursors for 3´UTR piRNA production in mice and chickens.
• Investigation of the role of post-termination 80S ribosomes in piRNA biogenesis.
• Examination of piRNA production during the pachytene stage of meiosis.

Main Results:

• 3´UTR piRNA precursors are identified as full-length mRNAs.
• Post-termination 80S ribosomes are shown to guide piRNA production on 3´UTRs.
• 3´UTR piRNA biogenesis occurs post-pioneer translation, degrading mRNAs and fine-tuning protein output.
• Embedded TEs in 3´UTR precursor mRNAs are targeted and cleaved by the produced piRNAs.

Conclusions:

• A novel function of the piRNA pathway in fine-tuning protein production is discovered.
• A conserved piRNA biogenesis mechanism recognizing translating RNAs in amniotes is revealed.
• 3´UTR piRNAs contribute to genome defense by targeting TEs within coding gene transcripts.