Association of chromosome territories with the nuclear matrix: Disruption of human chromosome territories correlates with the release of a subset of nuclear matrix proteins

To study the possible role of the nuclear matrix in chromosome territory or ganization, normal human fibroblast cells are treated in situ via classic i solation procedures for nuclear matrix in the absence of nuclease (e,g., DN ase I) digestion, followed by chromosome painting. We report for the first time that chromosome territories are maintained intact on the nuclear matri x. In contrast, complete extraction of the internal nuclear matrix componen ts with RNase treatment followed by 2 M NaCl results in the disruption of h igher order chromosome territory architecture, Correlative with territorial disruption is the formation of a faint DNA halo surrounding the nuclear la mina and a dispersive effect on the characteristically discrete DNA replica tion sites in the nuclear interior. Identical results were obtained using e ight different human chromosome paints. Based on these findings, we develop ed a fractionation strategy to release the bulk of nuclear matrix proteins under conditions where the chromosome territories are maintained intact. A second treatment results in disruption of the chromosome territories in con junction with the release of a small subset of acidic proteins. These prote ins are distinct from the major nuclear matrix proteins and may be involved in mediating chromosome territory organization.