BIOCHEMICAL AND MORPHOLOGICAL CHARACTERIZATION OF THE NUCLEAR MATRIX FROM APOPTOTIC HL-60 CELLS

We have characterized the nuclear matrix-intermediate filament fractio n from control and apoptotic HL-60 cells. Apoptosis was induced by exp osure to the topoisomerase I inhibitor, camptothecin. By means of two- dimensional polyacrylamide gel electrophoresis, striking qualitative a nd quantitative differences were seen in the protein composition of th e nuclear matrix-intermediate filament fraction obtained from apoptoti c cells in comparison with controls. Western blotting analysis of apop totic nuclear matrix proteins revealed degradation of some (topoisomer ase Il alpha, SAF-A) but not other (SATB1 and nucleolin) components. M oreover, immunofluorescent. staining for typical matrix antigens (NuMA protein, lamin B, SC-35) showed that in 35-40% of the structures prep ared from apoptotic samples, marked changes in the subnuclear distribu tion of these proteins were present. Striking morphological difference s between control and apoptotic samples were also detected at the ultr astructural level. These results demonstrate that both biochemical and morphological changes can be detected in the nuclear matrix prepared from apoptotic HL-60 cells. J. Cell. Biochem. 72:35-46, 1999. (C) 1999 Wiley-Liss, Inc.