Apoptosis in C3H/10T1/2 mouse embryonic cells: evidence for internucleosomal DNA modification in the absence of double-strand cleavage.

Apoptosis in embryonic C3H/10T1/2 (clone 8) cells is marked by specific changes in morphology and DNA fragmentation that differ from those found in apoptotic thymocytes. These results demonstrate that ultrastructural changes within the nucleus associated with endonucleolytic degradation are linked with structural degradation at higher levels of chromatin organization. Strand modifications within the internucleosomal linker region are shown to involve alkaline-sensitive sites that appear to be sensitive to S1 endonuclease. Our results suggest that apoptosis is not dependent upon internucleosomal cleavage and may reveal the penultimate step and the nature of the metabolic cascade that leads to cell death.