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pH-dependent DNA cleavage in permeabilized human fibroblasts
S Czene1, M Tibäck, M Harms-Ringdahl
1Department of Radiobiology, Stockholm University, S-106 91 Stockholm, Sweden.
The Biochemical Journal
|April 15, 1997
Summary
Intracellular acidification triggers DNA fragmentation in human fibroblasts via copper-mediated damage, mimicking an early stage of apoptosis. This pH-dependent DNA breakage is influenced by temperature and histones.
Area of Science:
- Cell Biology
- Biochemistry
- Molecular Biology
Background:
- Apoptosis, or programmed cell death, is often linked to intracellular acidification.
- A pH-dependent endonuclease is activated during apoptosis, suggesting a role for pH in DNA degradation.
Purpose of the Study:
- To investigate the impact of acidic pH on human fibroblast DNA.
- To elucidate the mechanisms underlying pH-dependent DNA fragmentation.
Main Methods:
- Permeabilization of human fibroblasts.
- Exposure to acidic pH conditions.
- Analysis of DNA fragmentation patterns.
- Assessment of protective agents like superoxide dismutase and copper chelators.
Main Results:
- Acidic pH induced cleavage of DNA into high-molecular-mass fragments in human fibroblasts.
- DNA fragmentation was modulated by temperature, histones, and diethyl pyrocarbonate.
- Superoxide dismutase and copper chelators inhibited DNA fragmentation, while catalase, DMSO, and Desferal did not.
Conclusions:
- Intracellular acidification can lead to DNA fragmentation through copper-mediated, site-specific DNA damage.
- This process contributes to the early phase of apoptosis, involving endonuclease activation.
- The findings highlight a novel mechanism of DNA damage linked to cellular acidity and copper ions.