[Analysis of the genome compartmentalization phenomenon in normal and neoplastic cells]

Intact cell nuclei (or whole cell lysates) were immobilized on Celite and extracted gradually with gradients of NaCl, LiCl-urea and temperature. Contrary to the notion of DNA integrity and continuity within chromosomes, a heterogeneous spectrum of DNA fragments of large size was obtained, adhesion of which to the nuclear interior widely varied. Similar chromatographic patterns of DNA were observed in analysis of various origin cells both in normal animal tissues and in malignant cells (Djungarian hamster fibroblasts transformed by SV40). Possible artefacts of apparent genome fragmentation caused by radioactive precursors or hydrodynamic shearing were checked up and ruled out as well as endogenous nucleases appear not to be involved in the phenomenon observed. DNA end-labelling in situ enabled to reveal pre-existence of DNA fragments in isolated nuclei.