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DNA fragmentation induced by a cytoplasmic extract from irradiated cells
H Kurihara1, S Torigoe, M Omura
1Department of Radiology, Yokohama City University School of Medicine, Yokohama, Japan.
Radiation Research
|September 5, 1998
Summary
Radiation-induced apoptosis involves a cytoplasmic signal activating caspase-3, leading to DNA fragmentation. This study identifies a potential extranuclear pathway initiating this cell death process.
Area of Science:
- Cell Biology
- Molecular Biology
- Radiation Biology
Background:
- Apoptosis, or programmed cell death, is characterized by DNA fragmentation and distinct morphological changes.
- The signaling pathways governing apoptosis, particularly those induced by radiation, are not fully understood.
- The primary site of radiation's effect in inducing apoptosis remains an open question.
Purpose of the Study:
- To investigate the extranuclear signaling events involved in radiation-induced apoptosis.
- To identify the key molecular players and pathways activated by gamma radiation leading to cell death.
Main Methods:
- Preparation of cytoplasmic extracts from gamma-irradiated HL60 cells.
- Incubation of normal HeLa S3 cell nuclei with these cytoplasmic extracts.
- Analysis of DNA fragmentation using agarose gel electrophoresis.
- Assessment of caspase activity using specific inhibitors (caspase-3 and ICE inhibitors).
Main Results:
- Cytoplasmic extracts from irradiated cells induced DNA fragmentation (DNA laddering) in normal nuclei.
- Caspase-3 activation was observed in the cytoplasmic extracts.
- The DNA fragmentation was inhibited by a caspase-3 inhibitor, but not by an ICE inhibitor.
Conclusions:
- A cytoplasmic signaling pathway, activated by gamma radiation, can induce apoptosis.
- Caspase-3 plays a crucial role in mediating radiation-induced DNA fragmentation.
- These findings suggest an extranuclear target of gamma radiation initiating a pathway upstream of caspase-3.