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A novel function for the DEAD-box RNA helicase DDX-23 in primary microRNA processing in Caenorhabditis elegans

Yu-De Chu1, Hsin-Kai Chen1, Tao Huang1

  • 1Graduate Institute of Microbiology, College of Medicine, National Taiwan University, Taipei 10051, Taiwan.

Developmental Biology
|November 26, 2015
PubMed

Insights

Two DEAD/H-box helicases, DDX-23 and DDX-17, are crucial for microRNA (miRNA) biogenesis in C. elegans. These proteins are essential for processing primary miRNAs (pri-miRNAs) into mature miRNAs, impacting various developmental pathways.

Area of Science:

  • * Molecular Biology
  • * Genetics
  • * Developmental Biology

Background:

  • * MicroRNA (miRNA) biogenesis is a fundamental process for gene regulation, involving the processing of primary miRNAs (pri-miRNAs) into mature miRNAs.
  • * In humans, DEAD-box helicases p68 (DDX5) and p72 (DDX17) are known to facilitate pri-miRNA cleavage by Drosha.
  • * The roles of DEAD/H-box proteins in miRNA processing in other organisms, particularly C. elegans, are less understood.

Purpose of the Study:

  • * To identify novel DEAD/H-box proteins involved in miRNA biogenesis using a candidate-based RNAi screen in C. elegans.
  • * To investigate the specific roles of identified helicases in the processing of pri-miRNAs.
  • * To determine if the identified helicases function in specific miRNA pathways, such as the heterochronic pathway.

Main Methods:

  • * Performed a candidate-based RNA interference (RNAi) screen in a sensitized let-7(mg279) C. elegans background.
  • * Knockdown of specific DEAD/H-box genes (DDX-23 and DDX-17) and assessed their impact on miRNA phenotypes.
  • * Measured levels of mature let-7 and pri-let-7 using molecular assays to determine the stage of miRNA processing affected.

Main Results:

  • * Knockdown of DDX-23 and DDX-17 enhanced let-7 loss-of-function phenotypes, indicating their involvement in let-7 processing or function.
  • * RNAi knockdown of ddx-23 and ddx-17 led to decreased mature let-7 levels and accumulation of pri-let-7, suggesting a role in pri-miRNA processing.
  • * DDX-23 and DDX-17 were found to be essential for the biogenesis of other heterochronic miRNAs (lin-4, miR-48, miR-84, miR-241) and the spatial patterning miRNA lsy-6.

Conclusions:

  • * C. elegans DDX-23 plays a novel role in pri-miRNA processing.
  • * DDX-17 has a conserved role in pri-miRNA processing, similar to its human homologs.
  • * These DEAD/H-box helicases are critical regulators of miRNA biogenesis across multiple developmental pathways in C. elegans.
Keywords:
C. elegansDDX-17DDX-23DEAD-box RNA helicaselet-7microRNA biogenesis

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