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Poly(ADP-ribose) polymerase cleavage during apoptosis: when and where?
C Soldani1, M C Lazzè, M G Bottone
1Dipartimento di Biologia Animale, Centro di Studio per I'Istochimica del CNR, Piazza Botta 10, Pavia, I-27100, Italy.
Experimental Cell Research
|September 26, 2001
Summary
Poly(ADP-ribose) polymerase-1 (PARP-1) activation, detected by ADP-ribose polymer synthesis, occurs early in apoptosis. PARP-1 proteolysis and cytoplasmic migration coincide with this activation.
Area of Science:
- Molecular Biology
- Cell Biology
- Biochemistry
Background:
- Poly(ADP-ribose) polymerase-1 (PARP-1) acts as a DNA nick sensor, synthesizing ADP-ribose from NAD+ upon DNA strand breaks.
- PARP-1 is proteolytically cleaved by caspases into 89 kDa (p89) and 24 kDa fragments during apoptosis.
- The interplay between PARP-1 activation and degradation during apoptosis remains incompletely understood.
Purpose of the Study:
- To investigate the temporal relationship between PARP-1 activation and its proteolytic degradation during apoptosis.
- To track the cellular localization of the PARP-1 p89 fragment in response to apoptotic stimuli.
Main Methods:
- Human Hep-2 cells were induced into apoptosis using actinomycin D.
- PARP-1 activity was monitored using mAb 10H, specific for ADP-ribose polymers.
- The presence and localization of the p89 proteolytic fragment were analyzed.
Main Results:
- Poly(ADP-ribose) synthesis, indicating PARP-1 activation, was observed as a very early response to the apoptotic stimulus.
- PARP-1 proteolysis by caspases occurred concurrently with poly(ADP-ribose) synthesis.
- The p89 fragment translocated from the nucleus to the cytoplasm in late apoptotic cells with significant nuclear fragmentation.
Conclusions:
- PARP-1 activation, evidenced by poly(ADP-ribose) synthesis, is an early event in actinomycin D-induced apoptosis.
- PARP-1 cleavage and subsequent p89 fragment migration into the cytoplasm are concomitant with its activation during apoptosis.