MUT-14 and SMUT-1 DEAD box RNA helicases have overlapping roles in germline RNAi and endogenous siRNA formation

Curr Biol. 2014 Apr 14;24(8):839-44. doi: 10.1016/j.cub.2014.02.060. Epub 2014 Mar 27.

Abstract

More than 2,000 C. elegans genes are targeted for RNA silencing by the mutator complex, a specialized small interfering RNA (siRNA) amplification module which is nucleated by the Q/N-rich protein MUT-16. The mutator complex localizes to Mutator foci adjacent to P granules at the nuclear periphery in germ cells. Here, we show that the DEAD box RNA helicase smut-1 functions redundantly in the mutator pathway with its paralog mut-14 during RNAi. Mutations in both smut-1 and mut-14 also cause widespread loss of endogenous siRNAs. The targets of mut-14 and smut-1 largely overlap with the targets of other mutator class genes; however, the mut-14 smut-1 double mutant and the mut-16 mutant display the most dramatic depletion of siRNAs, suggesting that they act at a similarly early step in siRNA formation. mut-14 and smut-1 are predominantly expressed in the germline and, unlike other mutator class genes, are specifically required for RNAi targeting germline genes. A catalytically inactive, dominant-negative missense mutant of MUT-14 is RNAi defective in vivo; however, mutator complexes containing the mutant protein retain the ability to synthesize siRNAs in vitro. The results point to a role for mut-14 and smut-1 in initiating siRNA amplification in germ cell Mutator foci, possibly through the recruitment or retention of target mRNAs.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Caenorhabditis elegans / genetics
  • Caenorhabditis elegans / metabolism*
  • Caenorhabditis elegans Proteins / genetics*
  • Caenorhabditis elegans Proteins / metabolism
  • DEAD-box RNA Helicases / metabolism*
  • Fluoroimmunoassay
  • Germ Cells / enzymology*
  • Germ Cells / physiology
  • Immunoprecipitation
  • Molecular Sequence Data
  • RNA Interference / physiology*
  • RNA, Small Interfering / biosynthesis*
  • Real-Time Polymerase Chain Reaction
  • Saccharomyces cerevisiae
  • Sequence Alignment
  • Sequence Analysis, DNA

Substances

  • Caenorhabditis elegans Proteins
  • RNA, Small Interfering
  • DEAD-box RNA Helicases
  • MUT-14 protein, C elegans
  • SMUT-1 protein, C elegans

Associated data

  • GEO/GSE54320