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Polypyrimidine tract-binding proteins are cleaved by caspase-3 during apoptosis
Sung Hoon Back1, Sejeong Shin, Sung Key Jang
1National Research Laboratory, Department of Life Science, Division of Molecular and Life Sciences, Pohang University of Science and Technology, San31, Hyoja-Dong, Pohang, Kyungbuk 790-784, Korea.
The Journal of Biological Chemistry
|May 11, 2002
Summary
During apoptosis, caspase-3 cleaves polypyrimidine tract-binding protein (PTB), inhibiting translation of internal ribosomal entry site (IRES) mRNAs. This cleavage regulates IRES-mediated translation during programmed cell death.
Area of Science:
- Molecular Biology
- Cell Biology
- Virology
Background:
- The polypyrimidine tract-binding protein (PTB) is crucial for internal ribosomal entry site (IRES)-mediated mRNA translation.
- Apoptosis involves programmed cell death pathways that can affect protein function and cellular processes.
Purpose of the Study:
- To investigate the effect of apoptosis-inducing agents on PTB.
- To determine the role of PTB cleavage by caspase-3 in regulating IRES-mediated translation during apoptosis.
Main Methods:
- Induction of apoptosis in cells using apoptosis-inducing agents.
- Analysis of PTB cleavage by caspase-3 using biochemical assays.
- Localization studies of PTB fragments using cell imaging.
- Assessment of IRES-mediated translation inhibition by PTB fragments.
Main Results:
- Apoptosis induction led to the cleavage of PTB isoforms 1, 2, and 4 by caspase-3 at three noncanonical sites.
- Cleavage separated PTB into N-terminal and C-terminal fragments.
- C-terminal PTB fragments localized to the cytoplasm and inhibited polioviral IRES-mediated translation.
Conclusions:
- Proteolytic cleavage of PTB by caspase-3 is a mechanism regulating IRES-containing mRNA translation during apoptosis.
- This regulation provides a link between apoptosis and translational control of specific viral and cellular mRNAs.