Nuclear Matrix Filaments Research Articles

Aberrant expression of nuclear matrix proteins during HMBA-induced differentiation of gastric cancer cells

To investigate the aberrant expression of nuclear matrix proteins in human gastric cancer cells before and after hexamethylene bisacetamide (HMBA) treatment. Proteomics analysis of differential nuclear matrix proteins was performed by two dimensional electrophoresis polyacrylamide gel electrophoresis and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry. The expression levels of three nuclear matrix proteins were further confirmed by Western blotting and their locations in nuclear matrix filament were observed by quantum dots-based immunofluorescence. Proteomics analysis showed that 43 protein spots were significantly changed due to HMBA treatment. Fifteen proteins were identified in the HMBA-induced differentiation of gastric tumor cells. Eight proteins spots were down-regulated while seven were up-regulated. Among these proteins, prohibitin, nucleophosmin and hnRNP A2/B1 were significantly decreased in HMBA-treated human gastric cancer cells, and their locations in nuclear matrix were altered by HMBA. Our results proved the alteration of specific nuclear matrix proteins during the differentiation of human gastric cancer cells. And the aberrant expressions of nuclear matrix proteins were of significance in revealing the regulatory mechanism of tumor cell proliferation and differentiation. The aberrant expressions and intracellular redistributions of nuclear matrix proteins before and after HMBA treatment indicated that nuclear matrix proteins play a pivotal role in the differentiation of gastric cancer cells.

Formation of nuclear matrix filaments by p27 BBP/eIF6

p27 BBP/eIF6 is an evolutionarily conserved protein necessary for ribosome biogenesis which was cloned in mammals for its ability to bind the cytodomain of β4 integrin. In cultured cells, a conspicuous fraction of p27 BBP/eIF6 is associated with the intermediate filaments/nuclear matrix (IF/NM) cytoskeleton. The mechanism of this association is not known. Here we show that in epidermis p27 BBP/eIF6 is naturally associated with IF/NM. To analyze the intrinsic capability of p27 BBP/eIF6 to generate cytoskeletal networks, the properties of the pure, recombinant, untagged protein were studied. Recombinant p27 BBP/eIF6 binds β4 integrin. Upon dialysis against IF buffer, p27 BBP/eIF6 forms polymers which, strikingly, have a morphology identical to NM filaments. Cross-linking experiments suggested that polymerization is favored by the formation of disulphide bridges. These data suggest that p27 BBP/eIF6 is associated with the cytoskeleton, and contributes to formation of NM filaments. These findings help to settle the controversy on nuclear matrix.

Effect of retinoic acid on the changes of nuclear matrix in termediate filament system in gastric carcinoma cells.

AIM:To explore the relationship between the configuration changes of the nuclear matrix intermediate filament system in cancer cell induced by retinoic acid and the malignant phenotypic reversion of cancer cells.METHODS:The human gastric adenocarcinoma cell line MGc80-3 cells were induced with 10(-6) mol/L retinoic acid and subcultured at cover slip strip and gold grids. The cells were treated by selective extraction method and prepared for whole mount electron microscopy observation. The samples were examined respectively with scanning and transmission electron microscope.RESULTS:The nuclear matrix filaments and intermediate filaments in MGc80-3 cells were relatively few and scattered, not well-distributed and arranged irregularly. The nuclear lamina was ununiformly thick and compact, connected to the nuclear matrix filaments and intermediate filaments relaxedly. However, the two kinds of filaments were abundant and well-distributed, different in slender and thick form and interweaved into a regular network in the cells induced by 10(-6)mol/L RA. The nuclear matrix filaments and inter-mediate filaments were connected closely by the thin and compact fiber-like lamina, and interlaced into a regular network throughout the whole cell region.CONCLUSION:The NM-IF system in MGc80-3 cells had undergone a restorational change similar to those of normal cells after RA inducement. This alternation is an important mor-phological and functional expression to the malignant phenotypic reversion of cancer cells.

Nuclear lamina and nuclear matrix organization in sperm pronuclei assembled in Xenopus egg extract.

Nuclear lamina and matrices were prepared from sperm pronuclei assembled in Xenopus egg extracts using a fractionation and extraction procedure. Indirect immunofluorescence revealed that while chromatin was efficiently removed from nuclei during the extraction procedure, the distribution of lamins was unaffected. Consistent with this data, the amount of lamin B3, determined by immunoblotting, was not affected through the extraction procedure. Nuclear matrices were visualised in DGD sections by TEM. Within these sections filaments were observed both at the boundary of the nucleus (the lamina) and within the body of the nucleus (internal nuclear matrix filaments). To improve resolution, nuclear matrices were also prepared as whole mounts and viewed using field emission in lens scanning electron microscopy (FEISEM). This technique revealed two distinct networks of filaments. Filaments lying at the surface of nuclear matrices interconnected nuclear pores. These filaments were readily labelled with monoclonal anti-lamin B3 antibodies. Filaments lying within the body of the nuclear matrix were highly branched but were not readily labelled with antilamin B3 antibodies. Nuclear matrices were also prepared from sperm pronuclei assembled in lamin B3 depleted extracts. Using FEISEM, filaments were also detected in these preparations. However, these filaments were poorly organised and often appeared to aggregate. To confirm these results nuclear matrices were also observed as whole mounts using TEM. Nuclear matrices prepared from control nuclei contained a dense array of interconnected filaments. Many (but not all) of these filaments were labelled with anti-lamin B3 antibodies. In contrast, nuclear matrices prepared from "lamin depleted nuclei' contained poorly organised or aggregated filaments which were not specifically labelled with anti-lamin B3 antibodies.

Nuclear lamina - like filaments and nuclear matrix in Allium cepa as revealed by scanning electron microscopy

In this study, freeze - fractured specimens of Allium cepa root tip meristems were examined under the scanning electron microscope (SEM). This technique permitted the visualization of the outer membrane of the nuclear envelope with nuclear pore complexes and polyribosomes. Some of the cell nuclei prepared with this procedure had fissures of various widths on their nuclear envelopes through which the nuclear lamina- like filaments (LLF) underneath the nucleoplasmic side of the envelopes were clearly visible. The diameters of these filaments varied between 25 and 125 nm. Many of the LLFs showed granular thickenings at places, and were attached to the inner surface of nuclear envelope in some regions. Similar LLFs were also seen at the peripheries of the freeze - fractured faces of nuclei. Meanwhile, the spatial relation between the nuclear matrix filaments (NMF) and other nuclear structures (nucleoli, chromatin and peripheral lamina - like filaments) was revealed in these fractured preparations. In addition, the methods and techniques in studying the nuclear lamina morphology and the roles played by NMFs in activities of various nuclear structures were discussed in brief.

Identification of the nuclear matrix and chromosome scaffold in dinoflagellate Crypthecodinium cohnii

Dinoflagellate is one of the primitive eukaryotes, whose nucleus may represent one of the transition stages from prokaryotic nucleoid to typical eukaryotic nucleus. Using selective extraction together with embeddment−free section and whole mount electron microscopy, a delicate nuclear matrix filament network was shown, for the first time, in dinoflagellate Crypthecodinium cohnii nucleus. Chromosome residues are connected with nuclear matrix filaments to form a complete network spreading over the nucleus. Moreover, we demonstrated that the dinoflagellate chromosome retains a protein scaffold after the depletion of DNA and soluble proteins. This scaffold preserves the characteristic morphology of the chromosome. Two dimensional electrophoreses indicated that the nuclear matrix and chromosome scaffold are mainly composed of acidic proteins. Our results demonstrated that a framework similar to the nuclear matrix and chromosome scaffold in mammalian cells appears in this primitive eukaryote,suggesting that these structures may have been originated from the early stages of eukaryote evolution.