Translation and codon usage regulate Argonaute slicer activity to trigger small RNA biogenesis

Area of Science:

• * Molecular Biology
• * Genetics
• * RNA Biology

Background:

• * Thousands of messenger RNAs (mRNAs) are expressed with antisense 22G-RNAs in the Caenorhabditis elegans germline.
• * These 22G-RNAs are loaded into the Argonaute CSR-1, which is essential for fertility and embryonic development.
• * The production mechanism of CSR-1 22G-RNAs remains largely unknown.

Purpose of the Study:

• * To elucidate the biogenesis pathway of CSR-1 22G-RNAs.
• * To investigate the role of CSR-1 slicer activity in small RNA production.
• * To understand how mRNA features regulate CSR-1 targeting and 22G-RNA synthesis.

Main Methods:

• * Analysis of small RNA synthesis triggered by CSR-1 activity.
• * Investigating the interplay between translation, codon optimality, and CSR-1-mediated RNA silencing.
• * Utilizing genetic manipulation in Caenorhabditis elegans.

Main Results:

• * CSR-1 slicer activity initiates small RNA synthesis on coding sequences of germline mRNAs.
• * Cleaved mRNAs recruit the RNA-dependent RNA polymerase EGO-1 to produce 22G-RNAs in phase with ribosomes.
• * Codon optimality and efficient translation inhibit CSR-1 slicing and 22G-RNA biogenesis.

Conclusions:

• * CSR-1-mediated slicing is a key trigger for 22G-RNA production during translation.
• * Codon usage in mRNA sequences may be a conserved mechanism to regulate small RNA biogenesis and Argonaute targeting.
• * This study reveals a novel pathway for small RNA generation linked to mRNA translation and sequence features.