• Journal of Microbiology and Biotechnology
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• v.17 no.11
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• pp.1856-1861
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• 2007

Physiological cell conditions such as glucose deprivation and hypoxia play roles in the development of drug resistance in solid tumors. These tumor-specific conditions cause decreased expression of DNA topoisomerase $II{\alpha}$, rendering cells resistant to topo II target drugs such as etoposide. Thus, targeting tumor-specific conditions such as a low glucose environment may be a novel strategy in the development of anticancer drugs. On this basis, we established a novel screening program for anticancer agents with preferential cytotoxic activity in cancer cells under glucose-deprived conditions. We recently isolated an active compound, AA-98, from Streptomyces sp. AA030098 that can prevent stress-induced etoposide resistance in vitro. Furthermore, LC-MS and various NMR spectroscopic methods identified AA-98 as mithramycin, which belongs to the aureolic acid group of antitumor compounds. We found that mithramycin prevents the etoposide resistance that is induced by glucose deprivation. The etoposide-chemosensitive action of mithramycin was just dependent on strict low glucose conditions, and resulted in the selective cell death of etoposide-resistant HT-29 human colon cancer cells.

• BMB Reports
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• v.31 no.5
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• pp.475-483
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• 1998

Many antibiotics contain partially deoxygenated sugar components that are usually essential for biological activity, affinity, structural stability, and solubility of antibiotics. Gene probes of the biosynthetic genes related with the deoxysugar were obtained from PCR. Primers were designed from the conserved peptide sequences of the known dTDP-D-glucose 4,6-dehydratases, which are the key step enzymes in the biosynthesis of deoxysugar. The primers were applied to amplify parts of dehydratase genes to 27 actinomycetes that produce the metabolites containing deoxysugar as structural constituents. About 180 and 340 bp DNA fragments from all of the actinomycetes were produced by PCR and analyzed by Southern blot and DNA sequencing. The PCR products were used as gene probes to clone the biosynthetic gene clusters for the antibiotic mithramycin, rubradirin, spectinomycin, and elaiophyrin. This method should allow for detecting of the biosynthetic gene clusters of a vast array of secondary metabolites isolated from actinomycetes because of the widespread existence of deoxysugar constituents in secondary metabolites.

• Journal of Microbiology
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• v.35 no.1
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• pp.40-46
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• 1997

The pWHM220 cosmid with a 24-kb insert cloned from Streptomyces albus ATCC 21838 induces the biosynthesis of a polysther antibiotic similar to salinomycin in Streptomyces invidans. We have analyzed this region by DNA sequencing as well as Southern blot hybridization with type I and type II polyketide synthase (PKS) probes. Surprisingly, we found another set of type II SKS genes only 10-kb from the original PKS genes, salABCDE. The DNA sequence revealed two complete open reading frames (ORFs) named salB2 and salC2, and one partial ORF that does not resemble any known DNA or deduced protein sequence. The salC2 should code for chain length determining factor while the deduced amino acid sequence encoded by salB2 exhibits high similarity to .betha.-ketoacyl synthase from different PKS gene clusters. The highest identity was found for .betha.-keetoacyl synthases from S. argillaceus (MtmP. 59.1% identity), the mithramycin producer and from S. venezuelae ISP5230 (JadA, 52.3% identity), the jadomycin producer. The SalC2 protein clearly resembles its counterparts in order aromatic PKS gene clusters that are believed to influence the length of the polyketide chain. The highest identities observed were to that of S. argillaceus (MtmK, 62.3%) and S. venezuelae ISP 5230 (JadB, 55.1%) proteins, Moreover, the deduced amino acid sequences of the salB2 and salC2 products were 29.0% identical.

• BMB Reports
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• v.42 no.8
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• pp.493-499
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• 2009

MicroRNAs (miRs) are a family of small noncoding RNAs that regulate gene expression by targeting mRNAs in a sequence specific manner, inducing translational repression or mRNA degradation. In this paper we have first analyzed by microarray the miR-profile in erythroid precursor cells from one normal and two thalassemic patients expressing different levels of fetal hemoglobin (one of them displaying HPFH phenotype). The microarray data were confirmed by RT-PCR analysis, and allowed us to identify miR-210 as an highly expressed miR in the erythroid precursor cells from the HPFH patient. When RT-PCR was performed on mithramycin-induced K562 cells and erythroid precursor cells, miR-210 was found to be induced in time-dependent and dose-dependent fashion, together with increased expression of the fetal $\gamma$-globin genes. Altogether, the data suggest that miR-210 might be involved in increased expression of $\gamma$-globin genes in differentiating erythroid cells.