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101.
In this study, Dendrobium officinale polysaccharide (named DOPS-1) was isolated from the stems of Dendrobium officinale by hot-water extraction and purified by using Sephadex G-150 column chromatography. The structural characterization, antioxidant and cytotoxic activity were carried out. Based on the results of HPLC, GC, Congo red experiment, together with periodate oxidation, Smith degradation, SEM, FT-IR, and NMR spectral analysis, it expressed that DOPS-1 was largely composed of mannose, glucose and galacturonic acid in a molar ratio of 3.2 : 1.3 : 1. The molecular weight of DOPS-1 was 1530 kDa and the main chain was composed of (1→4)-β-D-Glcp, (1→4)-β-D-Manp and 2-O-acetyl-(1→4)-β-D-Manp. The measurement results of antioxidant activity showed that DOPS-1 had the strong scavenging activities on hydroxyl radicals, DPPH radicals and superoxide radicals and the high reducing ability in vitro. Moreover, DOPS-1 was cytotoxic to all three human cancer cells of MDA-MB-231, A549 and HepG2. 相似文献
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The platelet-derived growth factor (PDGF) signaling pathway has been found to play important roles in the development and progression of human cancers by regulating the processes of cell proliferation, apoptosis, migration, invasion, metastasis, and the acquisition of the epithelial-mesenchymal transition (EMT) phenotype. Moreover, PDGF signaling has also been found to alter the expression profile of miRNAs, leading to the reversal of EMT phenotype. Although the role of miRNAs in cancer has been documented, there are very few studies documenting the cellular consequences of targeted re-expression of specific miRNAs. Therefore, we investigated whether the treatment of human pancreatic cancer cells with PDGF could alter the expression profile of miRNAs, and we also assessed the cellular consequences. Our study demonstrates that miR-221 is essential for the PDGF-mediated EMT phenotype, migration, and growth of pancreatic cancer cells. Down-regulation of TRPS1 by miR-221 is critical for PDGF-mediated acquisition of the EMT phenotype. Additionally, the PDGF-dependent increase in cell proliferation appears to be mediated by inhibition of a specific target of miR-221 and down-regulation of p27Kip1. 相似文献
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Lebars I Hu RM Lallemand JY Uzan M Bontems F 《The Journal of biological chemistry》2001,276(16):13264-13272
The T4 endoribonuclease RegB is involved in the inactivation of the phage early messengers. It cuts specifically in the middle of GGAG sequences found in early messenger intergenic regions but not GGAG sequences located in coding sequences or in late messengers. In vitro RegB activity is very low but is enhanced by a factor up to 100 by the ribosomal protein S1. In the absence of clear sequence motif distinguishing substrate and non-substrate GGAG-containing RNAs, we postulated the existence of a structural determinant. To test this hypothesis, we correlated the structure, probed by NMR spectroscopy, with the cleavage propensity of short RNA molecules derived from an artificial substrate. A kinetic analysis of the cleavage was performed in the presence and absence of S1. In the absence of S1, RegB efficiently hydrolyses substrates in which the last G of the GGAG motif is located in a short stem between two loops. Both strengthening and weakening of this structure strongly decrease the cleavage rate, indicating that this structure constitutes a positive cleavage determinant. Based on our results and those of others, we speculate that S1 favors the formation of the structure recognized by RegB and can thus be considered a "presentation protein." 相似文献
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Jiajia Ma Zijia Ren Yang Ma Lu Xu Ying Zhao Chaogu Zheng Yinghui Fang Ting Xue Baolin Sun Weihua Xiao 《The Journal of biological chemistry》2009,284(50):34600-34606
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