Abstract
Caspase-activated DNase (CAD) is a major apoptotic nuclease, responsible for DNA fragmentation and chromatin condensation during apoptosis. CAD is normally activated in apoptosis as a result of caspase cleavage of its inhibitory chaperone ICAD. Other aspects of CAD regulation are poorly understood. In particular, it has been unclear whether direct CAD activation in non-apoptotic living cells can trigger cell death. Taking advantage of the auxin-inducible degron (AID) system, we have developed a suicide system with which ICAD is rapidly degraded in living cells in response to the plant hormone auxin. Our studies demonstrate that rapid ICAD depletion is sufficient to activate CAD and induce cell death in DT40 and yeast cells. In the vertebrate cells, ectopic CAD activation triggered caspase activation and subsequent hallmarks of caspase-dependent apoptotic changes, including phosphatidylserine exposure and nuclear fragmentation. These observations not only suggest that CAD activation drives apoptosis through a positive feedback loop, but also identify a unique suicide system that can be used for controlling gene-modified organisms.
Highlights
Regulation and function of the apoptotic nuclease, caspase-activated DNase (CAD), remains obscure
Ectopic CAD activation triggered caspase activation and subsequent hallmarks of caspase-dependent apoptotic changes, including phosphatidylserine exposure and nuclear fragmentation. These observations suggest that CAD activation drives apoptosis through a positive feedback loop, and identify a unique suicide system that can be used for controlling gene-modified organisms
We demonstrate for the first time that ectopic activation of the nuclease CAD is sufficient to induce caspase-dependent apoptosis
Summary
Earnshaw‡4 From the ‡Wellcome Trust Centre for Cell Biology, University of Edinburgh, King’s Buildings, Max Born Crescent, Edinburgh EH9 3BF, Scotland, United Kingdom, the §Mayo Clinic, Rochester, Minnesota 55905, the ¶Centre for Frontier Research, National Institute of Genetics, ROIS, and Department of Genetics, SOKENDAI, Yata 1111, Mishima, Shizuoka 411-8540, Japan, and the ʈJapan Science and Technology Agency (JST), PREST, 4-1-8 Honcho, Kawaguchi, Saitama 332-0012, Japan
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