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971.
The use of ionizing radiation (IR) is essential for treating many human cancers. However, radioresistance markedly impairs the efficacy of tumor radiotherapy. IR enhances the production of reactive oxygen species (ROS) in a variety of cells which are determinant components in the induction of apoptosis. Much interest has developed to augment the effect of radiation in tumors by combining it with radiosensitizers to improve the therapeutic ratio. In the current study, the radiosensitizing effects of resveratrol and piperine on cancer cells were evaluated. Cancer cell lines treated with these natural products exhibited significantly augmented IR-induced apoptosis and loss of mitochondrial membrane potential, presumably through enhanced ROS generation. Applying natural products as sensitizers for IR-induced apoptotic cell death offers a promising therapeutic approach to treat cancer. 相似文献
972.
Isolation and characterization of a non-reducing polyketide synthase gene from the lichen-forming fungus Usnea longissima 总被引:1,自引:0,他引:1
Yi Wang Jung A Kim Yong Hwa Cheong Young Jin Koh Jae-Seoun Hur 《Mycological Progress》2012,11(1):75-83
Usnea longissima has long been used as a traditional medicine in China, India, Turkey, Canada and Europe. This lichen can produce several
bioactive compounds that primarily belong to the polyketide family. The enzymes responsible for the production of these compounds
are the polyketide synthases, but the biosynthetic processes in lichens are still unclear. In this study, a cultured mycobiont
of Usnea longissima was used to isolate and characterize a polyketide synthase gene (UlPKS1). Complete sequence information regarding UlPKS1 (6,468 bp) was obtained by screening a Fosmid genomic library using a 512-bp fragment corresponding to part of the ketosynthase
(KS) domain. Sequence analysis of UlPKS1 suggested that it contained features of a non-reducing fungal type I PKS with a starter unit of ACP transacylase (SAT), ketosynthase
(KS), product template (PT), acyl carrier protein (ACP) transacylase, acyltransferase (AT) and thioesterase (TE) domain, and
had five intervening introns. The domain organization of UlPKS1 (SAT-KS-AT-PT-ACP-ACP-TE) was quite similar to that of aromatic
PKSs, and phylogenetic analysis showed that UlPKS1 belonged to the clade of lichenized fungal non-reducing PKS. RT-PCR analyses revealed that the expression of UlPKS1 was down-regulated by glycine and high concentrations of sorbitol, inositol and fructose and up-regulated by sucrose and
glucose. Here, we introduce a non-reducing PKS gene in the lichen-forming fungus U. longissima, with a domain structure similar to the structure of orsellinic acid synthase A (OrsA) which is required for orsellinic acid biosynthesis in Aspergillus nidulans. 相似文献
973.
We provide an experimental demonstration of positive rheotaxis (rapid and continuous upstream motility) in wild-type Escherichia coli freely swimming over a surface. This hydrodynamic phenomenon is dominant below a critical shear rate and robust against Brownian motion and cell tumbling. We deduce that individual bacteria entering a flow system can rapidly migrate upstream (>20 μm/s) much faster than a gradually advancing biofilm. Given a bacterial population with a distribution of sizes and swim speeds, local shear rate near the surface determines the dominant hydrodynamic mode for motility, i.e., circular or random trajectories for low shear rates, positive rheotaxis for moderate flow, and sideways swimming at higher shear rates. Faster swimmers can move upstream more rapidly and at higher shear rates, as expected. Interestingly, we also find on average that both swim speed and upstream motility are independent of cell aspect ratio. 相似文献
974.
Yoon-Sun?Hur Ki-Hye?Shin Sunghan?Kim Kyoung?Hee?Nam Myeong-Sok?Lee Jong-Yoon?Chun Choong-III?CheonEmail author 《Molecules and cells》2009,27(2):217-223
Development of symbiotic root nodules in legumes involves the induction and repression of numerous genes in conjunction with
changes in the level of phytohormones. We have isolated several genes that exhibit differential expression patterns during
the development of soybean nodules. One of such genes, which were repressed in mature nodules, was identified as a putative
aldo/keto reductase and thus named Glycine max aldo/keto reductase 1 (GmAKR1). GmAKR1 appears to be a close relative of a yeast aldo/keto reductase YakC whose in vivo substrate has not been identified yet. The expression of GmAKR1 in soybean showed a root-specific expression pattern and inducibility by a synthetic auxin analogue 2,4-D, which appeared
to be corroborated by presence of the root-specific element and the stress-response element in the promoter region. In addition,
constitutive overexpression of GmAKR1 in transgenic soybean hairy roots inhibited nodule development, which suggests that it plays a negative role in the regulation
of nodule development. One of the Arabidopsis orthologues of GmAKR1 is the ARF-GAP domain 2 protein, which is a potential negative regulator of vesicle trafficking; therefore
GmAKR1 may have a similar function in the roots and nodules of legume plants.
These authors contributed equally to this work. 相似文献
975.
976.
Rangarajulu Senthil Kumaran Johnpaul Muthumary Eun-Ki Kim Byung-Ki Hur 《Biotechnology and Bioprocess Engineering》2009,14(1):76-83
Taxol is a highly functionalized anticancer drug widely used in hospitals and clinics. The leaf spot fungus, Phyllosticta dioscoreae was isolated from diseased leaves of Hibiscus rosa-sinensis and screened for extracellular production of taxol in M1D (Modified liquid medium) and PDB (Potato dextrose broth) medium
for the first time. The fungus was identified by its morphological and conidial features in the culture growth. The presence
of taxol in the fungal culture filtrate was confirmed by different spectroscopic and chromatographic analyses. The amount
of taxol produced was quantified by HPLC. The maximum amount of taxol produced was found to be 298 μg/L in M1D medium. Production
rate was 5.96 × 103 times faster than that found in culture broth of earlier reported fungus, Taxomyces andreanae. The extracted fungal taxol also showed strong cytotoxic activity in vitro in the cultures of human cancer cells tested by apoptotic assay. The results indicate that P. dioscoreae is an excellent source of taxol production, which suggests that the fungus has potential to undergo genetic engineering in
order to improve its production level. 相似文献
977.
Daniel Ng Hing Kah Chin Victor Vai Tak Wong 《Journal of industrial microbiology & biotechnology》2009,36(11):1345-1351
978.
Hwang-Phill Kim Young-Kwang Yoon Jin-Won Kim Sae-Won Han Hyung-Seok Hur Jinah Park Ju-Hee Lee Do-Youn Oh Seock-Ah Im Yung-Jue Bang Tae-You Kim 《PloS one》2009,4(6)
Background
Epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI) has been shown to exert a synergistic antitumor effect when combined with fluoropyrimidine. This synergy may be attributable to the downregulation of thymidylate synthase (TS), which is frequently overexpressed in fluoropyrimidine-resistant cancer cells. However, the molecular mechanism underlying the downregulation of TS has yet to be clearly elucidated.Methodology and Principal Findings
In this study, we demonstrate that lapatinib, a dual TKI of EGFR and HER2 downregulates TS via inhibition of the nuclear translocation of EGFR and HER2. From our cDNA microarray experiments, we determined that a variety of nucleotide synthesis-related genes, including TS, were downregulated with lapatinib, and this was apparent in HER2-amplified cells. Targeted and pharmacologic inhibition assays confirmed that the dual inhibition of EGFR and HER2 is required for the more effective reduction of TS as compared to what was observed with gefitinib or trasutuzumab alone. Additionally, we determined that co-transfected EGFR and HER2 activate the TS gene promoter more profoundly than do either EGFR or HER2 alone. The translocation of EGFR and HER2 into the nucleus and the subsequent activation of the TS promoter were inhibited by lapatinib.Conclusions and Significance
These results demonstrate that lapatinib inhibits the nuclear translocation of EGFR and HER2 and downregulates TS, thus sensitizing cancer cells to fluoropyrimidine. 相似文献979.
Karine Van Doninck Morgan L. Mandigo Jae H. Hur Peter Wang Julien Guglielmini Michel C. Milinkovitch William S. Lane Matthew Meselson 《PLoS genetics》2009,5(3)
Rotifers of Class Bdelloidea are remarkable in having evolved for millions of years, apparently without males and meiosis. In addition, they are unusually resistant to desiccation and ionizing radiation and are able to repair hundreds of radiation-induced DNA double-strand breaks per genome with little effect on viability or reproduction. Because specific histone H2A variants are involved in DSB repair and certain meiotic processes in other eukaryotes, we investigated the histone H2A genes and proteins of two bdelloid species. Genomic libraries were built and probed to identify histone H2A genes in Adineta vaga and Philodina roseola, species representing two different bdelloid families. The expressed H2A proteins were visualized on SDS-PAGE gels and identified by tandem mass spectrometry. We find that neither the core histone H2A, present in nearly all other eukaryotes, nor the H2AX variant, a ubiquitous component of the eukaryotic DSB repair machinery, are present in bdelloid rotifers. Instead, they are replaced by unusual histone H2A variants of higher mass. In contrast, a species of rotifer belonging to the facultatively sexual, desiccation- and radiation-intolerant sister class of bdelloid rotifers, the monogononts, contains a canonical core histone H2A and appears to lack the bdelloid H2A variant genes. Applying phylogenetic tools, we demonstrate that the bdelloid-specific H2A variants arose as distinct lineages from canonical H2A separate from those leading to the H2AX and H2AZ variants. The replacement of core H2A and H2AX in bdelloid rotifers by previously uncharacterized H2A variants with extended carboxy-terminal tails is further evidence for evolutionary diversity within this class of histone H2A genes and may represent adaptation to unusual features specific to bdelloid rotifers. 相似文献
980.