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Prothymosin alpha fragmentation in apoptosis
A G Evstafieva1, G A Belov, M Kalkum
1Belozersky Institute of Physico-Chemical Biology, Center of Molecular Medicine, Moscow State University, Moscow, Russia.
FEBS Letters
|February 17, 2000
Summary
During apoptosis, the nuclear protein prothymosin alpha fragments at a specific motif, preventing its nuclear accumulation and proliferation functions. This cleavage by caspase-3 and -7 disables its role in cell proliferation.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Prothymosin alpha is a crucial nuclear protein involved in cell proliferation.
- Apoptosis, or programmed cell death, involves complex molecular events including protein fragmentation.
- Understanding protein modifications during apoptosis is key to deciphering cell fate.
Purpose of the Study:
- To investigate the fragmentation of prothymosin alpha during apoptosis.
- To identify the specific cleavage site and enzymes responsible for prothymosin alpha fragmentation.
- To elucidate the functional consequences of prothymosin alpha fragmentation on its nuclear localization and proliferation-related activities.
Main Methods:
- Induction of apoptosis using various stimuli in human cells.
- Analysis of protein fragmentation patterns, specifically targeting prothymosin alpha.
- In vitro cleavage assays using purified caspases (caspase-3 and -7).
- Assessment of nuclear localization signals and protein nuclear uptake.
Main Results:
- Prothymosin alpha undergoes fragmentation during apoptosis.
- Cleavage occurs at the DDVD(99) motif, specifically at D(99) by caspase-3 and -7 in vitro.
- Caspase-mediated hydrolysis disrupts the nuclear localization signal of prothymosin alpha.
- The truncated protein loses its ability to accumulate within the nucleus.
Conclusions:
- Prothymosin alpha fragmentation is a specific event during apoptosis.
- Cleavage by caspases inactivates prothymosin alpha's nuclear functions.
- Fragmentation disables intranuclear proliferation-related functions by both peptide cleavage and impaired nuclear uptake.