排序方式: 共有1719条查询结果,搜索用时 46 毫秒
41.
MicroRNAs bind to and regulate the abundance and activity of target messenger RNA through sequestration, enhanced degradation, and suppression of translation. Although miRNA have a predominantly negative effect on the target protein concentration, several reports have demonstrated a positive effect of miRNA, i.e., increase in target protein concentration on miRNA overexpression and decrease in target concentration on miRNA repression. miRNA–target pair-specific effects such as protection of mRNA degradation owing to miRNA binding can explain some of these effects. However, considering such pairs in isolation might be an oversimplification of the RNA biology, as it is known that one miRNA interacts with several targets, and conversely target mRNA are subject to regulation by several miRNAs. We formulate a mathematical model of this combinatorial regulation of targets by multiple miRNA. Through mathematical analysis and numerical simulations of this model, we show that miRNA that individually have a negative effect on their targets may exhibit an apparently positive net effect when the concentration of one miRNA is experimentally perturbed by repression/overexpression in such a multi-miRNA multitarget situation. We show that this apparent unexpected effect is due to competition and will not be observed when miRNA interact noncompetitively with the target mRNA. This result suggests that some of the observed unusual positive effects of miRNA may be due to the combinatorial complexity of the system rather than due to any inherently unusual positive effect of the miRNA on its target. 相似文献
42.
43.
Wheat powdery mildew, caused by Blumeria graminis f. sp. tritici (Bgt), is one of the most consistently damaging diseases of common wheat worldwide and greatly affects crop productivity. Recently, several plant microRNAs (miRNAs) have been reported as gene expression regulators related to various adverse environments. However, up to now, less is known on the roles of miRNAs in powdery mildew infection response of wheat. In this study, miRNA expression patterns were investigated for identifying Bgt‐responsive miRNAs in wheat leaves using a plant miRNA microarray platform. A total of 79 miRNAs from 24 families were detected in wheat leaves. Among those, seven miRNAs were further validated to be involved in wheat powdery mildew response and two of them have never been reported. In addition, their target expression profiles showed a negative correlation with that of the seven miRNAs in mock‐ and Bgt‐infected samples furtherly proved, which in turn as the robust evidence, that those seven powdery mildew‐responsive miRNAs are highly reliable. These findings could extend the current view about miRNAs as ubiquitous regulators under stress conditions. 相似文献
44.
Background
The pathways regulating the transition of mammalian cells from quiescence to proliferation are mediated by multiple miRNAs. Despite significant improvements in our understanding of miRNA targeting, the majority of miRNA regulatory networks are still largely unknown and require experimental validation.Results
Here we identified miR-503, miR-103, and miR-494 as negative regulators of proliferation in primary human cells. We experimentally determined their genome wide target profiles using RNA-induced silencing complex (RISC) immunoprecipitations and gene expression profiling. Analysis of the genome wide target profiles revealed evidence of extensive regulation of gene expression through non-canonical target pairing by miR-503. We identified the proto-oncogene DDHD2 as a target of miR-503 that requires pairing outside of the canonical 5′ seed region of miR-503, representing a novel mode of miRNA-target pairing. Further bioinformatics analysis implicated miR-503 and DDHD2 in breast cancer tumorigenesis.Conclusions
Our results provide an extensive genome wide set of targets for miR-503, miR-103, and miR-494, and suggest that miR-503 may act as a tumor suppressor in breast cancer by its direct non-canonical targeting of DDHD2.Electronic supplementary material
The online version of this article (doi:10.1186/s12864-015-1279-9) contains supplementary material, which is available to authorized users. 相似文献45.
46.
47.
48.
49.
Amrita Datta Chaudhuri Savan Kabaria Doo Chul Choi M. Maral Mouradian Eunsung Junn 《The Journal of biological chemistry》2015,290(19):12425-12434
Parkinson disease is associated with decreased activity of the mitochondrial electron transport chain. This defect can be recapitulated in vitro by challenging dopaminergic cells with 1-methyl-4-phenylpyridinium (MPP+), a neurotoxin that inhibits complex I of electron transport chain. Consequently, oxidative phosphorylation is blocked, and cells become dependent on glycolysis for ATP production. Therefore, increasing the rate of glycolysis might help cells to produce more ATP to meet their energy demands. In the present study, we show that microRNA-7, a non-coding RNA that protects dopaminergic neuronal cells against MPP+-induced cell death, promotes glycolysis in dopaminergic SH-SY5Y and differentiated human neural progenitor ReNcell VM cells, as evidenced by increased ATP production, glucose consumption, and lactic acid production. Through a series of experiments, we demonstrate that targeted repression of RelA by microRNA-7, as well as subsequent increase in the neuronal glucose transporter 3 (Glut3), underlies this glycolysis-promoting effect. Consistently, silencing Glut3 expression diminishes the protective effect of microRNA-7 against MPP+. Further, microRNA-7 fails to prevent MPP+-induced cell death when SH-SY5Y cells are cultured in a low glucose medium, as well as when differentiated ReNcell VM cells or primary mouse neurons are treated with the hexokinase inhibitor, 2-deoxy-d-glucose, indicating that a functional glycolytic pathway is required for this protective effect. In conclusion, microRNA-7, by down-regulating RelA, augments Glut3 expression, promotes glycolysis, and subsequently prevents MPP+-induced cell death. This protective effect of microRNA-7 could be exploited to correct the defects in oxidative phosphorylation in Parkinson disease. 相似文献