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Interaction between Ski7p and Upf1p is required for nonsense-mediated 3'-to-5' mRNA decay in yeast

Shinya Takahashi1, Yasuhiro Araki, Takeshi Sakuno

  • 1Department of Physiological Chemistry, Graduate School of Pharmaceutical Sciences, University of Tokyo, Tokyo 113-0033, Japan.

The EMBO Journal
|July 26, 2003
PubMed

Insights

The nonsense-mediated decay (NMD) pathway degrades aberrant mRNAs. This study reveals a 3' to 5' decay pathway, involving Upf1p and Ski7p interactions, is crucial for NMD efficiency in yeast.

Area of Science:

  • Molecular Biology
  • Genetics
  • Biochemistry

Background:

  • Aberrant mRNAs with premature termination codons (PTC-mRNAs) are targeted for degradation by the conserved nonsense-mediated decay (NMD) pathway.
  • While NMD's role in 5' to 3' decay is established, the contribution of 3' to 5' decay pathways remains largely uncharacterized.

Purpose of the Study:

  • To investigate and characterize the 3' to 5' directed mRNA degradation within the yeast NMD pathway.
  • To elucidate the molecular mechanisms and key protein interactions governing this decay process.

Main Methods:

  • Utilized yeast genetics to assess PTC-mRNA stability in cells lacking 3' to 5' decay machinery components.
  • Investigated protein-protein interactions between NMD factors (Upf1p, Upf2p) and exosome-associated proteins (Ski7p) using co-immunoprecipitation or similar assays.
  • Employed overexpression studies of Ski7p N-domain fragments to assess their impact on PTC-mRNA degradation efficiency.

Main Results:

  • PTC-mRNAs were stabilized in yeast mutants deficient in 3' to 5' mRNA decay machinery.
  • The 3' to 5' degradation of PTC-mRNAs was significantly faster than that of normal transcripts and depended on the cytoplasmic exosome and Upf proteins.
  • A physical interaction between Upf1p and the Ski7p N-terminal domain was identified, requiring Upf2p, and its disruption impaired 3' to 5' NMD efficiency.

Conclusions:

  • The 3' to 5' decay pathway plays a significant role in yeast nonsense-mediated decay.
  • The interaction between Upf1p and the Ski7p N-terminal domain is critical for activating 3' to 5' directed NMD.

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