RNA channelling by the eukaryotic exosome.

Area of Science:

• Molecular Biology
• Structural Biology
• Biochemistry

Background:

• The eukaryotic exosome is a vital multi-subunit nuclease complex.
• It plays critical roles in RNA degradation, processing, and quality control.
• Understanding its structure and mechanism is key to RNA biology.

Purpose of the Study:

• To elucidate the structural basis of the Saccharomyces cerevisiae exosome function.
• To investigate the mechanism of RNA substrate interaction and translocation.
• To explore the evolutionary conservation of the exosome's mechanism.

Main Methods:

• Cryo-electron microscopy (Cryo-EM) for high-resolution structural determination.
• Generation of pseudo-atomic models for unbound and RNA-bound states.
• Comparative analysis of exosome structures across different functional states.

Main Results:

• Detailed structural reconstructions of the ten-subunit yeast exosome were obtained.
• Extra density at the exosome channel entry/exit sites suggests substrate threading.
• RNA-bound structures reveal the mechanism of RNA translocation through the exosome core.

Conclusions:

• The eukaryotic exosome employs a conserved substrate-threading mechanism for RNA processing.
• This channeling mechanism is likely ancient, present in the last common ancestor.
• Structural insights provide a foundation for understanding RNA metabolism and quality control.