AGO1 homeostasis involves differential production of 21-nt and 22-nt miR168 species by MIR168a and MIR168b.
BACKGROUND
AGO1 associates with microRNAs (miRNAs) and regulates mRNAs through cleavage and translational repression. AGO1 homeostasis entails DCL1-dependent production of miR168 from MIR168a and MIR168b transcripts, post-transcriptional stabilization of miR168 by AGO1, and AGO1-catalyzed miR168-guided cleavage of AGO1 mRNA.


RESULTS
This study reveals that MIR168a is highly expressed and predominantly produces a 21-nt miR168 species. By contrast, MIR168b is expressed at low levels and produces an equal amount of 21- and 22-nt miR168 species. Only the 21-nt miR168 is preferentially stabilized by AGO1, and consequently, the accumulation of the 22-nt but not the 21-nt miR168 is reduced when DCL1 activity is impaired. mir168a mutants with strongly reduced levels of 21-nt miR168 are viable but exhibit developmental defects, particularly during environmentally challenging conditions.


CONCLUSIONS
These results suggest that 22-nt miR168 ensures basal cleavage of AGO1 mRNA whereas 21-nt miR168 permits an effective response to endogenous or environmental fluctuations owing to its preferential stabilization by AGO1.
Vaucheret
Hervé
H
Laboratoire de Biologie Cellulaire, Institut Jean-Pierre Bourgin, INRA, Versailles, France. herve.vaucheret@versailles.inra.fr
D017360:Arabidopsis / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000502:physiology*; D060565:Argonaute Proteins; D001483:Base Sequence; D055162:Biocatalysis; D017931:DNA Primers; D017343:Genes, Plant; D006706:Homeostasis; D035683:MicroRNAs / Q000378:metabolism*; D009154:Mutation; D011401:Promoter Regions, Genetic
C117457:AGO1 protein, Arabidopsis; D029681:Arabidopsis Proteins; D060565:Argonaute Proteins; D017931:DNA Primers; D035683:MicroRNAs