CryoEM structure of yeast cytoplasmic exosome complex

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The eukaryotic RNA exosome complex is essential for RNA processing and decay.
• Ski7 is a key cofactor for the cytoplasmic exosome, targeting mRNAs for degradation.
• The precise interaction of Ski7 with the exosome and RNA substrate processing remains unclear.

Purpose of the Study:

• To elucidate the structural basis of Ski7-exosome interaction.
• To understand the mechanism of RNA substrate processing by the cytoplasmic exosome.

Main Methods:

• Single-particle cryo-electron microscopy (cryo-EM) was employed.
• Structures of the Ski7-exosome complex were determined in both RNA-free and RNA-bound states.

Main Results:

• Cryo-EM structures revealed Ski7's N-terminal domain mimics Rrp6's C-terminal domain interaction with the exosome.
• Analysis of RNA substrates with varying 3' overhangs suggests an RNA-induced activation switch.
• A through-core pathway for RNA processing by the exosome is supported.

Conclusions:

• The study provides the first structural insights into the Ski7-exosome complex.
• A novel RNA-induced activation mechanism for the exosome in mRNA turnover is proposed.