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101.
Despite the improvement of strategies against cancer therapy, the multidrug resistance (MDR)is the critical problem for successful
cancer therapy. Recurrent cancers after initial treatment with chemotherapy are generally refractory to second treatments
with these anticancer therapies. Therefore, it is necessary to elucidate the therapy-resistant mechanism for development of
effective therapeutic modalities against tumors. Here we demonstrate a phase-specific chemotherapy resistance due to epidermal
growth factor receptor (EGFR) in human breast cancer cells. Thymidine-induced G1-arrested cultures showed upregulated chemosensitivity,
whereas S-phase arrested cells were more resistant to chemotherapeutic agents. Overexpression of EGFR promoted the MDR phenotypes
in breast cancer cells via accelerating the G1/S phase transition, whereas depletion of EGFR exerted the opposite effects.
Furthermore, CyclinD1, a protein related to cell cycle, was demonstrated to be involved in above EGFR-mediated effects since
EGFR increased the expression of CyclinD1, and the specific RNA interference against CyclinD1 could primarily abolish the
EGFR-induced MDR phenotypes. These data provide new insights into the mode by which MDR breast cancers evade cytoxic attacks
from chemotherapeutic agents and also suggest a role for EGFR-CyclinD1 axis in this process. 相似文献
102.
Colussi F Garcia W Rosseto FR de Mello BL de Oliveira Neto M Polikarpov I 《European biophysics journal : EBJ》2012,41(1):89-98
Due to its elevated cellulolytic activity, the filamentous fungus Trichoderma harzianum (T. harzianum) has considerable potential in biomass hydrolysis application. Cellulases from Trichoderma reesei have been widely used in studies of cellulose breakdown. However, cellulases from T. harzianum are less-studied enzymes that have not been characterized biophysically and biochemically as yet. Here, we examined the effects
of pH and temperature on the secondary and tertiary structures, compactness, and enzymatic activity of cellobiohydrolase Cel7A
from T. harzianum (Th Cel7A) using a number of biophysical and biochemical techniques. Our results show that pH and temperature perturbations affect
Th Cel7A stability by two different mechanisms. Variations in pH modify protonation of the enzyme residues, directly affecting
its activity, while leading to structural destabilization only at extreme pH limits. Temperature, on the other hand, has direct
influence on mobility, fold, and compactness of the enzyme, causing unfolding of Th Cel7A just above the optimum temperature limit. Finally, we demonstrated that incubation with cellobiose, the product of
the reaction and a competitive inhibitor, significantly increased the thermal stability of Th Cel7A. Our studies might provide insights into understanding, at a molecular level, the interplay between structure and activity
of Th Cel7A at different pH and temperature conditions. 相似文献
103.
YQ Fan J Lee S Oh HJ Liu C Li YS Luan JM Yang HM Zhou ZR Lü YL Wang 《International journal of biological macromolecules》2012,51(5):845-858
The effects of osmolytes on the unfolding and refolding process of recombinant human brain-type creatine kinase (rHBCK) were comparatively, quantitatively studied in dilute solutions and macromolecular crowding systems (simulated by 100g/L polyethylene glycol 2000), respectively. The results showed that the osmolytes, including glycerol, sucrose, dimethylsulfoxide, mannitol, inositol, and xylitol, could both protect the rHBCK from denaturation induced by 0.8M GdnHCl and aid in the refolding of denatured-rHBCK in macromolecular crowding systems. When we examined the effects of sucrose and xylitol on the parameters of residual activity, reaction kinetics and intrinsic fluorescence of rHBCK during unfolding, it was found that the protecting effects of osmolytes in a macromolecular crowding system were more significant compared with those in a dilute solution, which resulted in more residual activities, protected the conformational changes and greatly decreased the rates of both the fast and slow tracks. Regarding the effects of glycerol, sucrose and mannitol on the denatured-rHBCK refolding parameters of refolding yield, reaction kinetics and aggregation, the results indicated that the osmolytes could alleviate the aggregation of rHBCK during refolding in both dilute solutions and macromolecular crowding systems, and the refolding yields and reaction rates under macromolecular crowding environment could be increased by the addition of osmolytes, though higher yields were obtained in the dilute solution. For further insight, osmolyte docking simulations and rHBCK denaturation were conducted successfully and confirmed our experimental results. The predictions based on the docking simulations suggested that the deactivation of guanidine may be blocked by osmolytes because they share common binding sites on rHBCK, and the higher number of interactions with rHBCK by osmolytes than guanidine may be one of the causes of rHBCK refolding. In brief, the additive effects of the exclusive volume effect from the macromolecular crowding system and the osmophobic effects from the osmolytes resulted in better performance of the osmolytes in a macromolecular crowding system, which also led to a better understanding of protein folding in the intracellular environment. 相似文献
104.
105.
Chromosome rearrangements during domestication of cucumber as revealed by high-density genetic mapping and draft genome assembly 总被引:2,自引:0,他引:2
Yang L Koo DH Li Y Zhang X Luan F Havey MJ Jiang J Weng Y 《The Plant journal : for cell and molecular biology》2012,71(6):895-906
Cucumber, Cucumis sativus L. is the only taxon with 2n = 2x = 14 chromosomes in the genus Cucumis. It consists of two cross‐compatible botanical varieties: the cultivated C. sativus var. sativus and the wild C. sativus var. hardwickii. There is no consensus on the evolutionary relationship between the two taxa. Whole‐genome sequencing of the cucumber genome provides a new opportunity to advance our understanding of chromosome evolution and the domestication history of cucumber. In this study, a high‐density genetic map for cultivated cucumber was developed that contained 735 marker loci in seven linkage groups spanning 707.8 cM. Integration of genetic and physical maps resulted in a chromosome‐level draft genome assembly comprising 193 Mbp, or 53% of the 367 Mbp cucumber genome. Strategically selected markers from the genetic map and draft genome assembly were employed to screen for fosmid clones for use as probes in comparative fluorescence in situ hybridization analysis of pachytene chromosomes to investigate genetic differentiation between wild and cultivated cucumbers. Significant differences in the amount and distribution of heterochromatins, as well as chromosomal rearrangements, were uncovered between the two taxa. In particular, six inversions, five paracentric and one pericentric, were revealed in chromosomes 4, 5 and 7. Comparison of the order of fosmid loci on chromosome 7 of cultivated and wild cucumbers, and the syntenic melon chromosome I suggested that the paracentric inversion in this chromosome occurred during domestication of cucumber. The results support the sub‐species status of these two cucumber taxa, and suggest that C. sativus var. hardwickii is the progenitor of cultivated cucumber. 相似文献
106.
Meng Q Zhao B Xu Q Xu X Deng G Li C Luan L Ren F Wang H Xu H Xu Y Zhang H Xiang JN Elliott JD Guo TB Zhao Y Zhang W Lu H Lin X 《Bioorganic & medicinal chemistry letters》2012,22(8):2794-2797
Novel indole-propionic acid derivatives were developed as sphingosine-1-phosphate (S1P) receptor agonists through a systematic SAR study. The optimized and S1P(3) selective S1P(1) agonist 9f induced peripheral blood lymphocyte reduction in vivo and has an excellent efficacy in mouse experimental autoimmune encephalomyelitis (EAE). 相似文献
107.
108.
Luan J Wang F Li Y Zhang B Zhang J 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》2012,125(4):781-791
Maize rough dwarf disease (MRDD) is one of the most serious virus diseases of maize worldwide, and it causes great reduction of maize production. In China, the pathogen was shown to be rice black-streaked virus (RBSDV). Currently, MRDD has spread broadly and leads to significant loss in China. However, there has been little research devoted to this disease. Our aims were to identify the markers and loci underlying resistance to this virus disease. In this study, segregation populations were constructed from two maize elite lines '90110', which is highly resistant to MRDD and 'Ye478', which is highly susceptible to MRDD. The F(2) and BC(1) populations were used for bulk sergeant analysis (BSA) to identify resistance-related markers. One hundred and twenty F(7:9) RILs were used for quantitative trait loci (QTL) mapping through the experiment of multiple environments over 3 years. Natural occurrence and artificial inoculation were both used and combined to determine the phenotype of plants. Five QTL, qMRD2, qMRD6, qMRD7, qMRD8 and qMRD10 were measured in the experiments. The qMRD8 on chromosome 8 was proved to be one major QTL conferring resistance to RBSDV disease in almost all traits and environments, which explained 12.0-28.9 % of the phenotypic variance for disease severity in this present study. 相似文献
109.
Begomovirus-whitefly mutualism is achieved through repression of plant defences by a virus pathogenicity factor 总被引:1,自引:0,他引:1
Plant-mediated interactions between herbivorous arthropods and pathogens transmitted by herbivores are important determinants of the population dynamics of both types of organisms in the field. The role of plant defence in mediating these types of tripartite interactions have been recognized but rarely examined especially at the physiological and molecular levels. Our previous work shows that a worldwide invasive whitefly can establish mutualism with the begomovirus Tomato yellow leaf curl China virus (TYLCCNV) via crop plants. Here, we show that TYLCCNV and betasatellite co-infection suppresses jasmonic acid defences in the plant. Impairing or enhancing defences mediated by jasmonic acid in the plant enhances or depresses the performance of the whitefly. We further demonstrate that the pathogenicity factor βC1 encoded in the betasatellite is responsible for the initiation of suppression on plant defences and contributes to the realization of the virus-vector mutualism. By integrating ecological, mechanistic and molecular approaches, our study reveals a major mechanism of the plant-mediated mutualism between a virus and its vector. As the test plant is an important economic crop, the results also have substantial implications for developing novel strategies for management of crop viruses and the insect vectors associated with them. 相似文献
110.
Jiang SY Bhalla R Ramamoorthy R Luan HF Venkatesh PN Cai M Ramachandran S 《Transgenic research》2012,21(4):785-795
Both drought and high salinity stresses are major abiotic factors that limit the yield of agricultural crops. Transgenic techniques have been regarded as effective ways to improve crops in their tolerance to these abiotic stresses. Functional characterization of genes is the prerequisite to identify candidates for such improvement. Here, we have investigated the biological functions of an Oryza sativa Ribosome-inactivating protein gene 18 (OSRIP18) by ectopically expressing this gene under the control of CaMV 35S promoter in the rice genome. We have generated 11 independent transgenic rice plants and all of them showed significantly increased tolerance to drought and high salinity stresses. Global gene expression changes by Microarray analysis showed that more than 100 probe sets were detected with up-regulated expression abundance while signals from only three probe sets were down-regulated after over-expression of OSRIP18. Most of them were not regulated by drought or high salinity stresses. Our data suggested that the increased tolerance to these abiotic stresses in transgenic plants might be due to up-regulation of some stress-dependent/independent genes and OSRIP18 may be potentially useful in further improving plant tolerance to various abiotic stresses by over-expression. 相似文献