Book of Abstracts: Albany 2007
June 19-23 2007
Activation of Poly(ADP-ribosyl)polymerase of Isolated Rat Liver Nuclei in Internucleosomal DNA Fragmentation
It is widely accepted that poly(ADP-ribosyl)polymerase (PARP-1) has an active and complex role in apoptosis. The general relationship between enzyme activity and apoptosis requires more detailed investigation of the role of PARP-1 in different stages of multi-step apoptotic transformations. Activation of PARP-1 is a common tranformation that results from DNA strand breakage when enzyme activity was determined in corresponding assay system in vitro. Activation of PARP-1 by DNA internucleosomal breakage in nuclei in apoptosis is less investigated. The data are contradictive due to complex interactions between cytoplasmic and nuclear systems engaged in apoptosis.
We investigated whether internucleosomal DNA fragmentation in isolated rat liver nuclei can contribute to PARP-1 activation and thus can account for the depletion of energetic resources of dying cells in terminal stages of apoptosis. The internucleosomal DNA fragmentation was induced by addition of Ca+2 è Mg+2 ions into isolated rat liver incubation media. The internucleosomal DNA fragmentation in isolated liver nuclei was apparent in 30 min. PARP-1 activity of nuclei was measured during 60 min incubation, when fragmentation was well established. Our results demonstrate, that DNA fragmentation associated with apoptosis drastically elevates PARP-1 activity in nuclei. This is to support the evidence that PARP-1 activation in final stages of apoptosis is rather the consequence than the cause of chromatin degradation.
Irina G. Artsruni
Yerevan State University