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The ubiquitin-proteasome pathway regulates survivin degradation in a cell cycle-dependent manner
1ICRF Molecular Oncology Unit, Imperial College School of Medicine, Hammersmith Campus, Du Cane Road, London W12 ONN, UK.
Abstract:
Survivin, a human inhibitor of apoptosis protein (IAP), plays an important role in both cell cycle regulation and inhibition of apoptosis. Survivin is expressed in cells during the G(2)/M phase of the cell cycle, followed by rapid decline of both mRNA and protein levels at the G(1) phase. It has been suggested that cell cycle-dependent expression of survivin is regulated at the transcriptional level. In this study we demonstrate involvement of the ubiquitin-proteasome pathway in post-translational regulation of survivin. Survivin is a short-lived protein with a half-life of about 30 minutes and proteasome inhibitors greatly stabilise survivin in vivo. Expression of the survivin gene under the control of the CMV promoter cannot block cell cycle-dependent degradation of the protein. Proteasome inhibitors can block survivin degradation during the G(1) phase and polyubiquitinated derivatives can be detected in vivo. Mutation of critical amino acid residues within the baculovirus IAP repeat (BIR) domain or truncation of the N terminus or the C terminus sensitises survivin to proteasome degradation. Together, these results indicate that the ubiquitin-proteasome pathway regulates survivin degradation in a cell cycle-dependent manner and structural changes greatly destabilise the survivin protein.
Insights
The ubiquitin-proteasome pathway regulates survivin degradation post-translationally. This pathway controls survivin protein levels during the cell cycle, impacting apoptosis and cell division.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Survivin, a human inhibitor of apoptosis protein (IAP), is crucial for cell cycle regulation and apoptosis inhibition.
- Survivin expression is cell cycle-dependent, peaking in G2/M and declining in G1.
- Previous research suggested transcriptional regulation of survivin's cell cycle-dependent expression.
Purpose of the Study:
- To investigate the post-translational regulation of survivin.
- To determine the role of the ubiquitin-proteasome pathway in survivin degradation.
- To elucidate how structural modifications affect survivin stability.
Main Methods:
- Utilized proteasome inhibitors to assess survivin stability in vivo.
- Examined survivin degradation during the G1 phase.
- Analyzed polyubiquitinated survivin derivatives.
- Introduced mutations in the baculovirus IAP repeat (BIR) domain and altered termini of survivin.
Main Results:
- Survivin is a short-lived protein (half-life ~30 minutes) stabilized by proteasome inhibitors.
- Proteasome inhibitors block survivin degradation in G1 and lead to detectable polyubiquitination.
- CMV promoter-driven survivin expression does not prevent cell cycle-dependent degradation.
- Mutations in the BIR domain or termini sensitize survivin to proteasome degradation.
Conclusions:
- The ubiquitin-proteasome pathway mediates cell cycle-dependent degradation of survivin.
- Survivin stability is influenced by its structural integrity, with modifications leading to destabilization.
- This study reveals a critical post-translational mechanism controlling survivin levels and function.