Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:5.99.1.2 (topoisomerase)
 9,166 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We have characterized the nuclear matrix-intermediate filament fraction from control and apoptotic HL-60 cells. Apoptosis was induced by exposure to the topoisomerase I inhibitor, camptothecin. By means of two-dimensional polyacrylamide gel electrophoresis, striking qualitative and quantitative differences were seen in the protein composition of the nuclear matrix-intermediate filament fraction obtained from apoptotic cells in comparison with controls. Western blotting analysis of apoptotic nuclear matrix proteins revealed degradation of some (topoisomerase IIalpha, SAF-A) but not other (SATB1 and nucleolin) components. Moreover, immunofluorescent staining for typical matrix antigens (NuMA protein, lamin B, SC-35) showed that in 35-40% of the structures prepared from apoptotic samples, marked changes in the subnuclear distribution of these proteins were present. Striking morphological differences between control and apoptotic samples were also detected at the ultrastructural level. These results demonstrate that both biochemical and morphological changes can be detected in the nuclear matrix prepared from apoptotic HL-60 cells.
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PMID:Biochemical and morphological characterization of the nuclear matrix from apoptotic HL-60 cells. 1002 65

Cell death in eukaryotes can occur by either apoptosis or necrosis. Apoptosis is characterized by well-defined nuclear changes which are thought to be the consequence of both proteolysis and DNA fragmentation. On the other hand, the nuclear modifications that occur during necrosis are largely less known. Here, we have investigated whether or not nuclear modifications occur during ethanol-induced necrotic cell death of HL-60 cells. By means of immunofluorescence staining, we demonstrate that the patterns given by antibodies directed against some nuclear proteins (lamin B1, NuMA, topoisomerase IIalpha, SC-35, B23/nucleophosmin) changed in necrotic cells. The changes in the spatial distribution of NuMA strongly resembled those described to occur during apoptosis. On the contrary, the fluorescent pattern characteristic for other nuclear proteins (C23/nucleolin, UBF, fibrillarin, RNA polymerase I) did not change during necrosis. By immunoblotting analysis, we observed that some nuclear proteins (SAF-A, SATB1, NuMA) were cleaved during necrosis, and in the case of SATB1, the apoptotic signature fragment of 70 kDa was also present to the same extent in necrotic samples. Caspase inhibitors did not prevent proteolytic cleavage of the aforementioned polypeptides during necrosis, while they were effective if apoptosis was induced. In contrast, lamin B1 and topoisomerase IIalpha were uncleaved in necrotic cells, whereas they were proteolyzed during apoptosis. Transmission electron microscopy analysis revealed that slight morphological changes were present in the nuclear matrix fraction prepared from necrotic cells. However, these modifications (mainly consisting of a rarefaction of the inner fibrogranular network) were not as striking as those we have previously described in apoptotic HL-60 cells. Taken together, our results indicate that during necrosis marked biochemical and morphological changes do occur at the nuclear level. These alterations are quite distinct from those known to take place during apoptosis. Our results identify additional biochemical and morphological criteria that could be used to discriminate between the two types of cell death. J. Cell. Biochem. Suppl. 36: 19-31, 2001.
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PMID:Nuclear changes in necrotic HL-60 cells. 1145 67

Recent studies suggest that DNA topoisomerase IIbeta (topo IIbeta) is involved in transcriptional activation of certain genes, which assumes accurate targeting of the enzyme to its action site. The target selection may be achieved by cooperation with unknown regulatory factors. To seek out such factors, we looked for proteins associated with the enzyme in differentiating cerebellar neurons. Antibody against topo IIbeta co-precipitated RNA-binding proteins including PSF, NonO/p54nrb, as well as hnRNP U/SAF-A/SP120. Reconstitution experiments with tag-purified proteins showed that topo IIbeta associates stoichiometrically with SP120 in the presence of RNA that was co-purified with SP120. The most effective RNA species for the complex formation was a subset of cellular polyadenylated RNAs. The C-terminal 187-residue domain of SP120 was necessary and sufficient for the association with both topo IIbeta and the endogenous RNA. The RNA isolated from the tag-purified SP120 inhibited the relaxation of supercoiled DNA by topo IIbeta. When the enzyme associates with SP120, however, the inhibition was abolished and the catalytic property was modulated to more processive mode, which may prolong its residence time at the genomic target site. Furthermore, the presence of SP120 was required for the stable expression of topo IIbeta in vivo. Thus, SP120 regulates the enzyme in dual ways.
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PMID:Regulation of DNA Topoisomerase IIbeta through RNA-dependent association with heterogeneous nuclear ribonucleoprotein U (hnRNP U). 2055 22

The sites of attachment of chromatin loops to the nuclear matrix (MARs) seem to harbor transcriptional enhancers, promoters and origins of replication (ORIs). According to the model proposed, the cooperative interactions among classical nuclear matrix proteins which are abundant (topoisomerase II, histone H1, HMG-I(Y), lamins A, B1, SAF-A, ARBP and others) bring together distant AT-rich classical MAR sequences causing looping of DNA. This process juxtaposes enhancers, ORIs, promoters, and other control elements that cohabit with MARs loaded with the less abundant transcription factors (TFs) facilitating productive interactions between enhancers and promoters or enhancers and core ORIs. The implications of the model in the interactions of oncoproteins with regulatory DNA elements and their integration into a chromatin and nuclear matrix environment are discussed.
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PMID:How enhancers work - juxtapositioning of DNA control elements by synergistic interaction of Mars - (review-hypothesis). 2155 74