The Nuclear Matrix: an Organizing Structure for the Interphase Nucleus and Chromosome
The interphase nucleus is characterized by a nuclear matrix structure that forms a residual scaffolding network composed of only 10% of the total nuclear proteins. The nuclear matrix contains residual elements of the pore-complex lamina, the nucleolus, and an intranuclear fibrous network. The matrix provides the basic shape and structure of the nucleus. In the interphase nucleus this nuclear matrix has been reported to be a central element in the organization of DNA loop domains and contains fixed sites for DNA replication and transcription. In this study, we have analyzed the role of the nuclear matrix and the DNA loop domains in the organization and structure of the number four human chromosome. A scale model is proposed and constructed that closely approximates the observed structural dimensions of this chromosome. The model is composed of equivalent 30 nm diameter filaments formed from solenoid with 6 nucleosomes per turn. This 30 nm solenoid filament is organized into loops of DNA each containing approximately 60,000 base pairs; each loop is anchored at its base to the nuclear matrix structure. A radial loop chromosome model containing 18 of these loops per turn forms a new unit of chromosome structure termed the miniband. Each miniband contains approximately one million base pairs of DNA and this is equivalent to a centimorgan in DNA content. Approximately 106 of these minibands are stacked longitudinally along a central axis to form the final chromatid. The role of the nuclear matrix in this organization is presented. The accuracy of the proposed model is tested by comparing its features with the known properties of the number four human chromosome.
KeywordsMetaphase Chromosome Nuclear Matrix Interphase Nucleus Loop Domain Nuclear Protein Matrix
Unable to display preview. Download preview PDF.
- 10.E. R. Barrack and D. S. Coffey, Hormone receptors and the nuclear matrix, in: “Gene Regulation by Steroid Hormones II,” A. K. Roy and J. H. Clark, eds., Springer-Verlag, New York (1983).Google Scholar
- 11.V. M. Dvorkin and B. D. Vanyushin, Replication and kinetics of the reassociation of DNA of the nuclear matrix of the regenerating rat liver, Biochem. (USSR) 43:1297–1301 (1978).Google Scholar
- 12.P. Dijkwel, L. Mullenders, and F. Wanka, Eucaryotic chromosome replication, in: “Annual Review of Genetics,” 9, E. Roman, ed., Annual Reviews, Inc., Palo Alto (1979).Google Scholar
- 21.R. Herman, L. Weymouth, and S. Penman, Heterogeneous nuclear RNA-protein fibers in chromatin-depleted nuclei, J. Cell Biol. 78:663 674 (1978).Google Scholar
- 38.G. P. Georgiev, S. A. Nedspasov, and V. U. Bakayev, Supranucleosomal levels of chromatin organization, in: “The Cell Nucleus,” 6, H. Busch, ed., Academic Press, New York (1978).Google Scholar
- 39.U. K. Laemmli, Levels of organization of the DNA in eukaryotic chromosomes, Pharmacol. Revs. 30:469–476 (1979).Google Scholar
- 42.J. Sedat and L. Manuelidis, A direct approach to the structure of eukaryotic chromosomes, CSHSQB XII:331–350 (1977).Google Scholar
- 45.E. J. Dupraw, “DNA and Chromosomes,” Holt, Rinehart, Winston, New York (1970).Google Scholar
- 50.U. K. Laemmli, J. Cell Sci., Suppl. 1 (1984).Google Scholar