• BMB Reports
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• 제29권1호
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• pp.27-31
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• 1996

Using topoisomerase II (topo II) isozyme-specific antibodies, we investigated the phosphorylation of topo $II{\alpha}$ in mitotic HeLa cells. Topo $II{\alpha}$ was specifically modified in the mitotic cells, resulting in slow migration on SDS-polyacrylamide gel electrophoresis. To characterize the nature of this modification, we treated the nuclear extracts prepared from the mitotic cells with alkaline phosphatase. After the treatment with alkaline phosphatase, the slowly migrated band disappeared and instead a normal (170 kDa) topo $II{\alpha}$ band appeared. These results indicate that human topo $II{\alpha}$ is modified at a specific site(s) in M phase by phosphorylation, supporting the possibility that M phase-specific phosphorylation of topo II is critical for mitotic chromosome condensation and segregation.

• Bulletin of the Korean Chemical Society
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• 제25권4호
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• pp.539-544
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• 2004

The ability of protoberberine alkaloids, berberine and berberrubine, to act as topoisomerase II poisons is linked to the anti-cancer activity. Minor alterations in structure have a significant effect on their relative activity. Berberine, which has methoxy group at the 19-position, is significantly less potent than berberrubine. Several observations support non-specific binding to HP14 by the berberine: (i) nonspecific upfield changes in $^1H$ chemical shift for protons of the berberine; (ii) the broadening of imino protons of HP14 upon binding of the berberine; (iii) very small increases in duplex melting temperature in the presence of the berberine. Our results reveal that substitution of a hydroxyl group to a methoxy group on the 19-position, thereby converting the berberrubine to the berberine is associated with a non-specific DNA binding affinity and a reduced topoisomerase II poisoning. The presence of a bulky 19-methoxy substituent decreases intercalating properties of berberine and makes it inactive as topoisomerase II poison.

• BMB Reports
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• 제31권3호
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• pp.245-248
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• 1998

Human epidermoid carcinoma A431 cells have an extraordinarily large number of epidermal growth factor (EGF) receptors, and their growth is inhibited by EGF, which results in growth arrest at the Gl phase. In order to investigate the EGF-mediated inhibition mechanism, the expression level of DNA topoisomerase (topo) II was analyzed after EGF treatment. As a result, it was shown that EGF treatment lowered the amount of 170 kDa topo II (topo $II{\alpha}$) but not 180 kDa (topo $II{\beta}$). However, the A431 cell variant resistant to EGF was not sensitive to EGF treatment. These results suggest that EGF-induced growth arrest of A431 cells may be closely related to the depletion of topo $II{\alpha}$.

• 한국미생물학회:학술대회논문집
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• 한국미생물학회 1991년도 춘계학술발표대회 논문집
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• pp.82-96
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• 1991

To understand the mechanism of illegitimate recombination in mammalian cells, we have examined the recombination role of DNA topoisomerase II (Topo II ). We found that purified calf thymus Topo II mediates recombination between two phage $\lambda$ DNA molecules in an in vitro system. The enzyme mainly produced a linear monomer recombinant DNA that can be packaged in vitro. Novobiocin and anti-calf thymus Topo II antibody inhibit this ATP-dependent recombination. The recombinant molecules contain duplications or deletion, and most crossovers take place between nonhomologous sequences of $\lambda$ DNA, as judged by the sequences of recombination junctions. In order to study the effects of Topo II on illegitimate recombination in mammalian cells, we have developed a new shuttle vector, pNKl, which contains three bacterial genes, amp(APR), galK and neo($Km^R$). Using this system, we have shown that a Topo II inhibitor, VM26, stimulated deletion formation in pNK1 DNA in monkey COS1 cells. Both in vitro and in vivo results suggest that Topo II participates in illegitimate recombination in mammalian cells.

• Natural Product Sciences
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• 제17권3호
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• pp.245-249
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• 2011

Eight compounds, squalene (1), friedelin (2), ${\beta}$-sitosterol (3), ${\beta}$-sitosterol-3-O-glucoside (4), ${\alpha}$-tocopherol (5), betulinic acid (6), trilinolein (7) and 1-O-(9Z,12Z-Octadecadienoyl)-3-nonadecanoyl glycerol (8), were isolated from the barks of Tilia amurensis. Their chemical structures were identified by comparing their physicochemical and spectral data with those published in the literature. These isolated compounds were examined for their inhibitory activities against topoisomerase I and II. Compound 7 showed significant inhibition of DNA topoisomerase I and II activities, with percent decreases in activity of 87 and 95%, respectively at a concentration of $100\;{\mu}M$. Compound 6 exhibited cytotoxicity against the human colon adenocarcinoma cell line (HT-29), the human breast adenocarcinoma cell line (MCF-7) and the human liver hepatoblastoma cell line (HepG-2), with $IC_{50}$ values of 20, 59 and $16\;{\mu}M$, respectively.

• 대한의생명과학회지
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• 제10권4호
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• pp.507-514
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• 2004

The Pseudomonas aeruginosa isolated from the clinical specimens has a mutation on the QRDR (quinolone resistance determining region). There were obvious mutations in both gyrA and parC gene which are major targets of quinolone. Simultaneous mutations were found two sites or more on these genes in all of ten strains. GyrB or parE gene had only silent mutation without converted amino acids. We confirmed that P. aeruginosa from clinical specimens exhibited decreased sensitivity to fluroquiolone due to changed Thr-83→lle and Asp-87→Asn types on gyrA and altered Ser-87→Leu type on parC. This is the first finding that a new Met-93→Thr type on parC as well as mutations on gyrB or parE genes differed from existing patterns. This study showed more mutations of gyrA rather than parC, suggesting that change of Type Ⅳ topoisomerase is more serious than that of type Ⅱ (DNA gyrase).

• 한국환경성돌연변이발암원학회지
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• 제9권1호
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• pp.13-22
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• 1989

The effect of novobiocin (NOV), and inhibitor of topoisomerase II, on ethyl methanesulfonate (EMS)-or bleomycin (BLM)-induced DNA repair synthesis was examined during the cell cycle of Chinese hamster ovary (CHO)-K1 cells. Three assays were employed in this study: cell survival, alkaline elution and unscheduled DNA synthesis. EMS was effective at killing CHO cells in G1 phase, wheras BLM preferentially killed cells in G2 and S phases. EMS induced the much more amount of DNA damage in G1 phase, while BLM induced in G2 phase than the other phases. The both of pre- and post-treatment with BOV inhibitied EMS- or BLM-induced DNA repair synthesis in G1 and G2 phases, and pretreatment with NOV inhibited more effectively than the post-treated group. These results suggested that CHO cells exhibited a differential sensitivity to cell lethality and DNA damage in relation to cell cycle according to used chemical agents, and that DNA topoisomerase II participated in an initial stage of DNA repair.

• Natural Product Sciences
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• 제13권4호
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• pp.359-364
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• 2007

Three known ${\alpha}$-amyrin triterpenoids, ursolic acid (1), $2{\alpha},3{\alpha}$-dihydro xyurs-12-ene-28-oic acid (2) and euscaphic acid (3), and ${\beta}$-amyrin triterpenoid, $3{\beta}$-hydroxyolean-5,12-diene (4), and ${\alpha}$-spinasterol (5) have been isolated from the fractionated n-butanol extracts of the spikes of Prunella vulgaris var. lilacina, guided by DNA topoisomerases I and II inhibitory activities and cytotoxic activity against human cancer cells. Their structures were elucidated on the basis of spectroscopic and chemical methods. Compound 4 exhibited significant cytotoxic activity against human colon adenoblastoma (HT-29), and 5 showed DNA topoisomerase I and II inhibitions.

• Tuberculosis and Respiratory Diseases
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• 제42권3호
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• pp.302-313
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• 1995

연구배경: 종양괴사인자(Tumor necrosis factor; TNF)는 다양한 생물학적인 작용을 가지며 종양 세포에 대한 세포 독성은 그 대표적인 기능중의 하나이다. TNF-$\alpha$는 생체외에서(in vitro) 몇몇 종양 세포주에 대하여 항암제, 특히 topoisomerase II targeted chemotherapeutic agent의 세포 독성 효과를 상승적으로 증가시키는 것이 알려져 있다. 최근 암세포에 대한 cytokine 유전자 요법에서 TNF는 중요한 대상으로 여겨지고 있으며, 유전자 이입에 의해 암조직이 TNF를 생성하게 될 경우 암 증식 억제 효과가 있음이 보고되고 있다. 연구자는 암세포에 TNF-$\alpha$ 유전자를 이입하여 자신이 TNF-$\alpha$를 생성하도록 형질을 변환시킨 암세포는 topoisomerase II 억제 항암제에 대한 김수성에 변화가 있을 것이라는 가설을 수립하였고 이를 검증하고자 본 연구를 수행하였다. 본 연구에서는 생체외로(in vitro) TNF-$\alpha$ 유전자를 이입하여 TNF-$\alpha$를 생성하는 암세포주에서 topoisomerase II targeted drug에 대한 항암제 감수성 효과가 모세포주에 비하여 증대될 수 있는지를 알아 보고자하였다. 방법: TNF-$\alpha$에 감수성을 보이는 것으로 알려진 인체 중피종 세포주인 NCI-H2058 세포주 및 생쥐의 섬유육종 세포주인 WEHI164 세포주와 인체 비소세포 폐암 세포주인 A549 세포주를 배양하여, 먼저 임상에서 흔히 폐암의 항암 화학 요법 치료에 널리 쓰이는 대표적인 topoisomerase II targeted chemotherapeutic drug인 etoposide(VP-16)와 doxorubicin(adriamycin)을 가하였을 때 관찰된 세포 독성을 MTT assay로 측정하고, 각 모세포주(parenta1 cell line)에 TNF-$\alpha$의 유전자를 이입시켜서 형절 변환한 세포주(transformed cell line)에 대하여 각각 동일한 항암제를 가하였을 때 관찰된 세포 독성의 정도를 같은 방법으로 측정하여, 그 결과를 비교 분석하였다. 또한 모세포주에 외부에서 TNF를 가하여 전처치한 후 동일한 항암제를 가하였을 때의 세포독성을 관찰하여 비교 분석하였다. 결과: H2058 세포주에서는 TNF-$\alpha$ 유전자를 이입한 세포주 topoisomerase II targeted drug을 가하였을 때, 항암제 감수성이 모세포주에 같은 항암제를 가하였을 때에 비하여 의미있게 증가함을 관찰할 수 있었으나(p<0.05), WEHI 세포주와 A549 세포주에 있어서는 TNF-$\alpha$ 유전자를 이입한 세포주에서 모세포주에 비하여 항암제 감수성이 증가하지는 않았다. 결론: TNF-$\alpha$ 유전자의 이입이 topoisomerase II targeted chemotherapeutic drug에 대한 항암제 감수성을 증가시키는 효과는 세포주에 따라 다양한 결과를 보이는 것을 알 수 있었으며, 적어도 선택된 특정 종류의 호흡기계 암세포에 있어서는 TNF-$\alpha$ 유전자의 이입으로 항암제 감수성(chemosensitivity)을 증가시킬 수 있을 것으로 사료된다.

• 대한약학회:학술대회논문집
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• 대한약학회 2002년도 Proceedings of the Convention of the Pharmaceutical Society of Korea Vol.2
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• pp.315.1-315.1
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• 2002

DNA topoisomerases I (topo I) and II are essential enzymes that relax DNA supercoiling and relieve torsional strain during DNA processing. including replication. transcription. and repair. Topo I relaxes DNA by cleaving one strand of DNA by attacking a backbone phosphale with a catalytic lyrosine (Tyr723. human topo I). This enzyme has recently been investigated as a new target for antineoplastic drugs. Inhibitors to the enzyme intercalate between the DNA base pairs. interfering religation of cleaved DNA, therefore inhibit the activity of topo I. (omitted)