Uridylation of mature miRNAs and siRNAs by the MUT68 nucleotidyltransferase promotes their degradation in Chlamydomonas

Fadia Ibrahim, Linda A. Rymarquis, Eun Jeong Kim, James Becker, Eniko Balassa, Pamela J. Green, Heriberto Cerutti

Research output: Contribution to journalArticlepeer-review

116 Scopus citations


Regulation of gene expression by small RNAs(′20-30 nucleotides in length) plays an essential role in developmental pathways and defense responses against genomic parasites in eukaryotes. Micro-RNAs (miRNAs) and small interfering RNAs (siRNAs) commonly direct the inactivation of cognate sequences through a variety of mechanisms, including RNA degradation, translation inhibition, and transcriptional repression. Recent studies have provided considerable insight into the biogenesis and the mode of action of miRNAs and siRNAs. However, relatively little is known about mechanisms of quality control and small RNA decay in RNA interference (RNAi) pathways. Here we show that deletion of MUT68, encoding a terminal nucleotidyltransferase in the alga Chlamydomonas reinhardtii, results in elevated miRNA and siRNA levels. We found that MUT68 plays a role in the untemplated uridylation of the 3′ ends of small RNAs in vivo and stimulates their degradation by the RRP6 exosome subunit in vitro. Moreover, RRP6 depletion also leads to accumulation of small RNAs in vivo. We propose that MUT68 and RRP6 cooperate in the degradation of mature miRNAs and siRNAs, as a quality control mechanism to eliminate dysfunctional or damaged small RNA molecules.

Original languageEnglish (US)
Pages (from-to)3906-3911
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Issue number8
StatePublished - Feb 23 2010
Externally publishedYes


  • Exosome
  • RNA interference
  • miRNA quality control

ASJC Scopus subject areas

  • General


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