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Uridylation of miRNAs by hen1 suppressor1 in Arabidopsis

Guodong Ren1, Xuemei Chen, Bin Yu

  • 1Center for Plant Science Innovation and School of Biological Sciences, University of Nebraska, Lincoln, NE 68588-0660, USA.

Current Biology : CB
|April 3, 2012
PubMed

Insights

The HESO1 enzyme uridylates unmethylated microRNAs (miRNAs) and small interfering RNAs (siRNAs) in plants. This process destabilizes these RNAs, impacting their abundance and function.

Area of Science:

  • Plant molecular biology
  • RNA biology
  • Epigenetics

Background:

  • HEN1-mediated 2'-O-methylation protects plant and animal small RNAs from degradation.
  • The enzymes responsible for uridylating unmethylated small RNAs in HEN1 mutants were previously unknown.

Purpose of the Study:

  • To identify the enzyme responsible for uridylation of unmethylated small RNAs in Arabidopsis HEN1 mutants.
  • To elucidate the role of this uridylation process in small RNA metabolism and stability.

Main Methods:

  • Genetic screening to identify suppressors of hen1 mutations.
  • Characterization of the identified suppressor gene HESO1.
  • Analysis of small RNA profiles in wild-type, hen1, and HESO1-overexpressing Arabidopsis plants.

Main Results:

  • A novel enzyme, HESO1, was identified as a terminal nucleotidyl transferase that adds uridines to the 3' end of unmethylated small RNAs.
  • HESO1-mediated uridylation affects the profile and abundance of microRNAs (miRNAs) and small interfering RNAs (siRNAs) in hen1 mutants.
  • Overexpression of HESO1 exacerbates morphological defects and reduces miRNA accumulation in hen1 mutants, suggesting uridylation can destabilize unmethylated miRNAs.

Conclusions:

  • HESO1 is the primary enzyme responsible for uridylating unmethylated miRNAs and siRNAs in Arabidopsis.
  • RNA uridylation may destabilize unmethylated small RNAs and potentially compete with exoribonuclease activity.
  • Findings have implications for understanding piRNA uridylation in animals.

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