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Lessons from structural and biochemical studies on the archaeal exosome
Sophia Hartung1, Karl-Peter Hopfner
1Center for Integrated Protein Science and Gene Center, Department of Chemistry and Biochemistry, Ludwig-Maximilians-University Munich, Feodor-Lynen-Strasse 25, 81377 Munich, Germany.
Biochemical Society Transactions
|January 16, 2009
Summary
The RNA exosome, a protein complex, degrades RNA. Archaeal exosomes have a unique structure enabling efficient RNA processing, but their reversible activity differs from eukaryotic mechanisms.
Area of Science:
- Molecular Biology
- Biochemistry
- Structural Biology
Background:
- The RNA exosome is a crucial multisubunit exonuclease complex.
- It plays a vital role in RNA maturation and degradation across eukaryotes and archaea.
- Archaeal exosomes share similarities with bacterial polynucleotide phosphorylates.
Purpose of the Study:
- To elucidate the structural and functional characteristics of archaeal exosomes.
- To understand the mechanism of RNA degradation by archaeal exosomes.
- To explore the evolutionary divergence of RNA processing mechanisms between archaea and eukaryotes.
Main Methods:
- Structural analysis of archaeal exosomes.
- Biochemical assays to determine RNA degradation activity.
- Comparative analysis of archaeal and eukaryotic exosome functions.
Main Results:
- Archaeal exosomes possess a large processing chamber with three 3'-->5' phosphorolytic active sites.
- A narrow entry pore, associated with RNA-binding domains, facilitates high processivity and protects structured RNA.
- The phosphorolytic activity is reversible, allowing the formation of heteropolymeric tails from nucleoside diphosphates.
Conclusions:
- The unique structure of archaeal exosomes enables highly processive and regulated RNA degradation.
- The reversible nature of archaeal exosome activity is a key difference compared to eukaryotic systems.
- Separation of polyadenylation and nuclease activities in the human exosome evolved to manage reversible phosphorolytic activity.
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