PRESENCE OF DNASE GAMMA-LIKE ENDONUCLEASE IN NUCLEI OF NEURONAL DIFFERENTIATED PC12 CELLS

DNase gamma, which cleaves chromosomal DNA into nucleosomal units (DNA ladder formation), has been suggested to be the critical component of apoptotic machinery. Using rat pheochromocytoma PC12 cells, which are differentiated to sympathetic neurons by nerve growth factor (NGF), w e investigated whether DNase;l-like enzyme is present in neuronal cell s and is involved in neuronal cell death. The nuclear autodigestion as say for DNase catalyzing internucleosomal DNA cleavage revealed that n uclei from neuronal differentiated PC12 cells Contain acidic and neutr al endonucleases, while nuclei from undifferentiated PC12 cells have o nly acidic endonuclease. The DNA ladder formation observed in isolated nuclei from neuronal differentiated PC12 cells at neutral pH requires both Ca2+ and Mg2+, and is sensitive to Zn2+. The molecular mass of t he neutral endonuclease present in neuronal differentiated PC12 cell n uclei is 32000 as determined by activity gel analysis (zymography), Th e properties of the neuronal endonuclease present in neuronal differen tiated PC12 cell nuclei were similar to those of purified DNase gamma from rat thymocytes and splenocytes. Interestingly, in neuronal differ entiated PC12 cells, internucleosomal DNA fragmentation is observed fo llowing NGF deprivation, whereas undifferentiated PC12 cells fail to e xhibit DNA ladder formation during cell death by serum starvation, The se results suggest that the DNase gamma-like endonuclease present in n euronal differentiated PC12 cell nuclei is involved in internucleosoma l DNA fragmentation during apoptosis, induced by NGF deprivation.