DNA fragmentation induced by a cytoplasmic extract from irradiated cells.
Apoptosis is a mode of cell death characterized by distinct morphological features and DNA fragmentation. The program that leads to apoptosis has been considered to be predominantly extranuclear, and a signal transduction pathway to the nucleus exists during apoptosis, while characteristic events occur in the nucleus. As for radiation-induced apoptosis, the signal transduction pathway remains unclear, especially the sites where the primary effect of radiation occurs. In this study, we demonstrate that a cytoplasmic extract prepared from irradiated cells has the ability to cause DNA fragmentation and that caspase-3 is activated in this extract. Normal nuclei of HeLa S3 cells were added to a cytoplasmic extract made from HL60 cells which had been irradiated with 30 Gy of 137Cs gamma rays and were incubated. Agarose gel electrophoresis of the added nuclei showed a characteristic DNA laddering pattern. This reaction was blocked by a caspase-3 inhibitor but not by an ICE inhibitor. These observations suggest that a signal transduction pathway from an unknown target of gamma radiation may exist upstream of caspase-3 during radiation-induced apoptosis.
Kurihara
H
H
Department of Radiology, Yokohama City University School of Medicine, Yokohama, Japan.
Torigoe
S
S
Omura
M
M
Saito
K
K
Kurihara
M
M
Matsubara
S
S
D053148:Caspase 3; D020169:Caspases; D002457:Cell Extracts; D002474:Cell-Free System; D002588:Cesium Radioisotopes; D003546:Cysteine Endopeptidases / Q000187:drug effects / Q000378:metabolism*; D053938:DNA Fragmentation; D004789:Enzyme Activation / Q000187:drug effects / Q000528:radiation effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005720:Gamma Rays; D018922:HL-60 Cells / Q000528:radiation effects; D006367:HeLa Cells / Q000528:radiation effects; D006801:Humans; D009842:Oligopeptides / Q000494:pharmacology; D015398:Signal Transduction / Q000528:radiation effects
D002457:Cell Extracts; D002588:Cesium Radioisotopes; D004791:Enzyme Inhibitors; D009842:Oligopeptides; C099158:acetyl-aspartyl-glutamyl-valyl-aspartal; C096429:L 709049; C505407:CASP3 protein, human; D053148:Caspase 3; D020169:Caspases; D003546:Cysteine Endopeptidases