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Ubiquitin recognition by the proteasome
1Laboratory of Protein Metabolism, Tokyo Metropolitan Institute of Medical Science, 2-1-6 Kamikitazawa, Setagaya-ku, Tokyo 156-8506, Japan.
Abstract:
The 26S proteasome is a 2.5-MDa complex responsible for the selective, ATP-dependent degradation of ubiquitylated proteins in eukaryotic cells. Substrates in hundreds cellular pathways are timely ubiquitylated and converged to the proteasome by direct recognition or by multiple shuttle factors. Engagement of substrate protein triggers conformational changes of the proteasome, which drive substrate unfolding, deubiquitylation and translocation of substrates to proteolytic sites. Recent studies have challenged the previous paradigm that Lys48-linked tetraubiquitin is a minimal degradation signal: in addition, monoubiquitylation or multiple short ubiquitylations can serve as the targeting signal for proteasomal degradation. In this review, I highlight recent advances in our understanding of the proteasome structure, the ubiquitin topology in proteasome targeting, and the cellular factors that regulate proteasomal degradation.
Insights
The 26S proteasome degrades ubiquitylated proteins, with new research showing monoubiquitylation also signals protein degradation. This review covers proteasome structure, ubiquitin signals, and regulatory factors.
Area of Science:
- Biochemistry
- Molecular Biology
- Cell Biology
Background:
- The 26S proteasome is a large complex crucial for regulated protein degradation in eukaryotic cells.
- Protein degradation is vital for numerous cellular processes, including cell cycle control and signal transduction.
- Ubiquitylation serves as a key signal for targeting proteins to the proteasome.
Purpose of the Study:
- To review recent advances in understanding the 26S proteasome.
- To explore the role of different ubiquitin topologies in proteasome targeting.
- To highlight cellular factors regulating proteasomal degradation.
Main Methods:
- Literature review of recent studies on proteasome structure and function.
- Analysis of research on ubiquitin signaling in protein degradation.
- Synthesis of information on regulatory mechanisms of the proteasome.
Main Results:
- The 26S proteasome's structure and mechanism of substrate degradation are complex and dynamic.
- Recent findings expand the known ubiquitin signals for proteasomal degradation beyond Lys48-linked tetraubiquitin.
- Monoubiquitylation and other short ubiquitin chains can also target proteins for degradation.
Conclusions:
- The paradigm for proteasomal substrate targeting is evolving with new insights into ubiquitin signaling.
- A deeper understanding of proteasome regulation is essential for comprehending cellular homeostasis.
- Future research will likely uncover more intricate details of proteasome-ubiquitin interactions and regulation.
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