The 180-kDa isoform of topoisomerase II is localized in the nucleolus and belongs to the structural elements of the nucleolar remnant

Zini, Nicoletta; Martelli, Alberto M.; Sabatelli, Patrizia; Santi, Spartaco; Negri, C.; Ricotti, G.; Maraldi, N. M.

doi:10.1016/0014-4827(92)90196-f

Cited by 89 publications

(38 citation statements)

References 25 publications

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“…Consistent with this, we observed positive staining for topoisomerase I13 in virtually all cells in all tissues and tumours. Previous studies using antibodies that recognise a 150-kDa protein, presumed to be a breakdown product of topoisomerase 1I, have suggested that this isoform is localized exclusively to nucleoli (Zini et al, 1992). Using those antibodies, D'Andrea et al (1994) studied expression of the 150-kDa antigen in melanoma and lung cancer and observed a poor correlation of the expression of this protein with proliferation.…”

Section: Ow Cancer Research Campaign 1997mentioning

confidence: 99%

The distribution and expression of the two isoforms of DNA topoisomerase II in normal and neoplastic human tissues

Turley

Comley²,

Houlbrook³

et al. 1997

Br J Cancer

149

111

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Summary In mammalian cells, there are two isoforms of DNA topoisomerase 11, designated a (170-kDa form) and ,B (180-kDa form). Previous studies using cell lines have shown that the topoisomerase Ila and [ isoforms are differentially regulated during the cell cycle and in response to changes in growth state. Moreover, both isoforms can act as targets for a range of anti-tumour drugs. Here, we have analysed the normal tissue distribution in humans of topoisomerase Ila and f using isoform-specific antibodies. In addition, we have studied expression of these isoforms in 69 primary tumour biopsies, representative either of tumours that are responsive to topoisomerase 11-targeting drugs (breast, lung, lymphoma and seminoma) or of those that show de novo drug resistance (colon). Topoisomerase lla was expressed exclusively in the proliferating compartments of all normal tissues, and was detectable in both the cell nucleus and cytoplasm. In biologically aggressive or rapidly proliferating tumours (e.g. high-grade lymphomas and seminomas), there was a high level of topoisomerase Ila, although expression was still detectable in colon tumours, indicating that expression of this isoform is not sufficient to explain the intrinsic drug resistance of colon tumours. Topoisomerase Ill was expressed ubiquitously in vivo and was localized in both the nucleoli and the nucleoplasm. This isoform was present in quiescent cell populations, but was expressed at a generally higher level in all tumours and proliferating cells than in normal quiescent tissues. We conclude that topoisomerase Ila is a strict proliferation marker in normal and neoplastic cells in vivo, but that topoisomerase ll[ has a much more general cell and tissue distribution than has topoisomerase Ila. The apparent up-regulation of topoisomerase II,B in neoplastic cells has implications for the response of patients to anti-tumour therapies that include topoisomerase Il-targeting drugs.Keywords: topoisomerase Ila; topoisomerase P; immunochemistry Topoisomerase II is a homodimeric nuclear protein with many different roles in DNA metabolism, including relief of torsional stress and mitotic chromosome condensation and segregation (reviewed in Wang, 1985(reviewed in Wang, , 1991Watt and Hickson, 1994). Topoisomerase II is also one of the most important determinants of cellular sensitivity to a range of clinically important anti-tumour drugs. For example, topoisomerase II is the primary cellular target for several intercalating agents, including doxorubicin, mitoxantrone and epirubicin, as well as for the non-intercalating epipodophyllotoxins, etoposide and teniposide (reviewed in Osheroff et al, 1991;Pommier, 1993;Beck et al, 1993). Topoisomerase II is a so-called type II enzyme, defined as acting via the creation of double-stranded breaks in DNA, through which an intact DNA duplex is passed, before the break is resealed. As part of this breakage and religation process, a transient reaction intermediate is generated, termed the cleavage complex, consisting of a topoisomerase...

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Section: Ow Cancer Research Campaign 1997mentioning

confidence: 99%

The distribution and expression of the two isoforms of DNA topoisomerase II in normal and neoplastic human tissues

Turley

Comley²,

Houlbrook³

et al. 1997

Br J Cancer

149

111

View full text Add to dashboard Cite

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“…They not only differ in their biophysical and biochemical properties but are also differentially regulated during the cell cycle (Capranico et al 1992;Woessner et al 1991) (also reviewed by Hwang and Hwong 1994). The 180-kD ␤ -isozyme is mainly localized in the nucleolus, and it has been suggested that it may represent a structural element for the spatial organization and the transcriptional regulation of ribosomal genes (Zini et al 1992).…”

mentioning

confidence: 99%

Detection of Human Topoisomerase IIα in Cell Lines and Tissues: Characterization of Five Novel Monoclonal Antibodies

Kellner

Heidebrecht

Rudolph

et al. 1997

J Histochem Cytochem.

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SUMMARYWe report five novel monoclonal antibodies (Ki-S1, Ki-S4, Ki-S6, Ki-S7, and Ki-S8) reactive with a proliferation-related nuclear antigen. In immunoprecipitation and Western blot experiments using crude nuclear extracts, they recognized a protein of 170 kD that, after proteolytic digestion of the immunoprecipitate and sequencing of the resulting peptides, was identified as the ␣ -isoform of human topoisomerase II. This was confirmed by testing the antibodies on a highly purified enzyme preparation. Crossreactivity with topoisomerase II ␤ was ruled out by testing the antibodies on crude extracts from yeast cells expressing the ␤ -isoform exclusively. The antibodies bind the antigen with different affinities and at different epitopes, apparently located within the carboxyl third of the enzyme. All five antibodies are suitable for archival material after adequate antigen retrieval, thereby enabling retrospective studies. This report illustrates the tissue and subcellular distribution of the antigen through the cell cycle by immunohistochemistry and confocal fluorescence microscopy. The antibodies will be useful tools in further analysis of morphological and functional aspects of topoisomerase II and may serve diagnostic purposes, as well as providing prognostic information in tumor pathology. (J Histochem Cytochem 45:251-263, 1997)

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“…However, the results of these studies are not unambiguous. Some studies describe a diffuse distribution of topoisomerase IIa in the nucleoplasm and an exclusively nucleolar localization of topoisomerase 11p [29,38,471. Conversely, other studies report both isoenzymes in the nucleoplasm and in the nucleolus in similar proportions [36].…”

Section: Discussionmentioning

confidence: 99%

“…Moreover, it is controversial whether topoisomerase IIa is distributed in the nucleoplasm diffusely [29] or in a dishomogeneous fashion 136, 39,461. It is also not known if topoisomerase I1 is a fixed component of the nuclear matrix or a freely diffusible enzyme: it can be prepared as a component of matrix or scaffold structures from nuclei and mitotic chromosomes [38,481. However, it has been observed that 70% of the enzyme leaves the nucleus and diffuses into the cytosol during one cell cycle [49].…”

Section: Discussionmentioning

confidence: 99%

“…The observation that topoisomerase IIP is mainly located in the nucleolus and predominantly expressed during the G2 phase has led to the speculation that this isoenzyme is mainly involved in gene transcription. Conversely, topoisomerase IIa is believed to be mainly involved in DNA synthesis [5,36,38,471. Under this assumption, the relocation of a major portion of topoisomerase IIa from the nucleoplasm to the nucleolus should make a cell more resistant to the cytotoxic effects of topoisomerase I1 inhibition, which are believed to be mainly effected during DNA synthesis [lo-131.…”

Section: Discussionmentioning

confidence: 99%

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A drug‐resistant variant of topoisomerase IIα in human HL‐60 cells exhibits alterations in catalytic pH optimum, DNA binding and sub‐nuclear distribution

Boege

Kjeldsen

Gieseler

et al. 1993

European Journal of Biochemistry

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Anion-exchange chromatography of partially purified human HL-60 topoisomerase IT resolves the known a (170 kDaj and / 3 (180 kDa) isoenzymes at 150 mM NaCl and 230 mh4 NaCl, respectively. An additional topoisomerase I1 fraction was eluted by > 300 mM NaCl. It could be identified by Western blotting as a late-eluting variant of topoisomerase IIa, which is functionally altered as compared to the early-eluting form, having the following properties: a shift in the catalytic optimum to pH 9 ; increased stability in DNA complex formation; approximately 100-fold resistance to orthovanadate ; approximately 1000-fold resistance to the cytostatic substances N-[4-(9-acridinylamino)-3-methoxyphenyl]-methanesulphonamide (amsacrine) and the podophyllotoxin etoposide (VP 16). 80% of the late-eluting topoisomerase IIa could be captured by SDS on calf thymus DNA without further enhancement by drugs. In contrast, the early-eluting topoisomerase IIa exhibits 10% complex formation with SDS alone, and an increase to 90% complex formation in the presence of drugs. A HL-60 subline (HL-60/R), approximately 1000-fold resistant to etoposide and amsacrine, has equivalent proportions of topoisomerase IIa and topoisomerase IIP and similar levels of both isoenzymes, as compared to the drug-sensitive HL-60/WT cells. However, determination of the cellular levels of the early-eluting and late-eluting forms of topoisomerase IIa revealed that the HLdO/R cell line contains approximately 80% of the late-eluting topoisomerase IIa, whereas the sensitive HL-60/WT cell line contains only 1 5 2 0 % of this form. The nuclear distribution of the two forms also differs. Sensitive HL-60/WT cells show a diffuse nuclear distribution but in resistant cells the distribution is localized in the nucleoli. Apparently two functionally distinct subforms of topoisomerase IIa coexist in drug-sensitive and drug-resistant HL-60 cells and changes in their relative levels affect the cellular sensitivity to topoisomerase-11-targeting drugs.Type I1 DNA topoisomerases are enzymes that regulate the topological state of DNA by a process in which DNA strands are passed through transient enzyme-bridged doublestranded DNA breaks. These enzymes appear to be closely related to chromosomal structures and are thought to play a crucial role in cellular processes such as DNA synthesis, -).Note. Dedicated to Professor Ernst J. M. Helmreich on the occasion of his 70th birthday. by separate genes. They differ in molecular mass (170 kDa and 180 kDaj, biochemical and pharmacological properties [8] and are differently expressed during the cell cycle and differentiation [5, 91. Type I1 topoisomerases have recently been identified as the cellular targets for a number of important antineoplastic agents. These include DNA-intercalating agents such as N-amide (amsacrine), doxorubicin and mitoxantrone, as well as agents that lack intercalating activity, such as etoposide and teniposide. The topoisomerase I1 mediated DNA strand breaks which are induced by these agents are thought to be respon...

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The 180-kDa isoform of topoisomerase II is localized in the nucleolus and belongs to the structural elements of the nucleolar remnant

Cited by 89 publications

References 25 publications

The distribution and expression of the two isoforms of DNA topoisomerase II in normal and neoplastic human tissues

The distribution and expression of the two isoforms of DNA topoisomerase II in normal and neoplastic human tissues

Detection of Human Topoisomerase IIα in Cell Lines and Tissues: Characterization of Five Novel Monoclonal Antibodies

A drug‐resistant variant of topoisomerase IIα in human HL‐60 cells exhibits alterations in catalytic pH optimum, DNA binding and sub‐nuclear distribution

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