Nuclear matrix: isolation and characterization of a framework structure from rat liver nuclei

Abstract

A nuclear framework structure termed the nuclear matrix has been isolated and characterized. This matrix forms the major residual structure of isolated nuclei and consists largely of protein with smaller amounts of RNA, DNA, carbohydrate, and phospholipid. The nuclear matrix can be further resolved by combined treatment with DNase and RNase. The remaining nuclear protein structure, after extraction of 90% of the nuclear protein, 99.9% of the DNA, and 98% of the RNA and phospholipid, is termed the nuclear protein matrix. Electron microscopy of this final nuclear protein matrix reveals an interior framework structure composed of residual nucleolar structures associated with a granular and fibrous internal matrix structure. The internal matrix framework is derived from the interchromatinic structures of the nucleus, and is connected to a surrounding residual nuclear envelope layer containing residual nuclear pore complex structures.Sodium dodecyl sulfate-acrylamide gel electrophoresis of the nuclear matrix proteins demonstrates three major polypeptide fractions, P-l, P-2, and P-3, with average molecular weights of -69,000, 66,000 and 62,000, as well as several minor polypeptides which migrate at -50,000 and at higher molecular weights (>100,000). Polypeptides with molecular weights identical to those of P-l, P-2, and P-3 are also components of isolated nuclear envelopes and nucleoli, whereas isolated chromatin contains no detectable matrix polypeptides. This suggests that the major matrix polypeptides are localized in specific structural regions of the nucleus, i.e., nuclear envelope, nucleoli, and interchromatinic structures. The presence of cytochrome oxidase activity in the isolated nuclear matrix indicates that at least some integral proteins of the nuclear membrane are associated with the matrix.Preliminary communications from our laboratory (12-14) have reported the isolation of a residual framework structure derived from rat liver nuclei, and termed the nuclear protein matrix, or more generally the nuclear matrix. Aside from serving as a skeletal framework, the nuclear matrix may

The amino terminus targets the mixed lineage leukemia (MLL) protein to the nucleolus, nuclear matrix and mitotic chromosomal scaffolds

“…[43][44][45] A precursor-product relationship between the two scaffolds has been proposed, where the metaphase chromosome organization is in part maintained by the same nuclear matrix proteins, like topoisomerase II, which organize interphase chromatin. 46 Topoisomerase II is the major component of both interphase and metaphase scaffolds and it is thought to bind at SARs positioned at the base of the chromatin loops.…”

“…The scaffolding of metaphase chromosomes is also believed to be derived from this matrix. [43][44][45] To test the possibility that MLL might be associated with the nuclear matrix and chromosomal scaffolds, we used immunofluorescence microscopy to evaluate the relative locations of MLL3AT and topoisomerase II, a major component of the proteinaceous scaffolds. [46][47][48][49] HeLa cells expressing MLL3AT were labeled with ␣-FLAG mAb (fluorescein) and an ␣-topoisomerase II polyclonal antibody (Texas red), and then examined by fluorescence or confocal laser scanning microscopy.…”

The association of transcribed genes with the nuclear matrix ofDrosophilacells during heat shock

“…This structure has been defined In two ways. Morphologically, the structures remaining after extraction of nuclei with salt to remove most histones and other proteins appear to represent a proteinaceous network of fibers as observed by electron microscopy (3)(4)(5), although the composition and morphology of these structures has engendered considerable controversy (6,7).…”

Tropomyosin is localized in the nuclear matrix and chromosome scaffold of physarum polycephalum

“…Many authors have analysed the protein composition of the nuclear matrix and chromosome scaffold with the SDS-PAGE technique [1,10,19,[24][25][26], but their results did not give an unequivocal view about the composition as different materials and methods were used in their experiments. Since nuclear matrix and chromosome scaffold are complicated and dymanic complex of proteins, and, moreover, protein gel electrophoresis itself can not identify the individual proteins, so further understanding of the components of the nuclear matrix and chromosome scaffold is still necessary…”