Previous studies have indicated the important roles of MYCN in tumorigenesis and progression of neuroblastoma (NB), the most common extracranial solid tumor derived from neural crest in childhood. However, the regulatory mechanisms of MYCN expression in NB still remain largely unknown. In this study, through mining public microarray databases and analyzing the cis-regulatory elements and chromatin immunoprecipitation data sets, we identified CCCTC-binding factor (CTCF) as a crucial transcription factor facilitating the MYCN expression in NB. RNA immunoprecipitation, RNA electrophoretic mobility shift assay, RNA pull down and in vitro binding assay indicated the physical interaction between CTCF and MYCN opposite strand (MYCNOS), a natural noncoding RNA surrounding the MYNC promoter. Gain- and loss-of-function studies revealed that MYCNOS facilitated the recruitment of CTCF to its binding sites within the MYCN promoter to induce chromatin remodeling, resulting in enhanced MYCN levels and altered downstream gene expression, in cultured NB cell lines. CTCF cooperated with MYCNOS to suppress the differentiation and promote the growth, invasion and metastasis of NB cells in vitro and in vivo. In clinical NB tissues and cell lines, CTCF and MYCNOS were upregulated and positively correlated with MYCN expression. CTCF was an independent prognostic factor for unfavorable outcome of NB, and patients with high MYCNOS expression had lower survival probability. Taken together, these results demonstrate that CTCF cooperates with noncoding RNA MYCNOS to exhibit oncogenic activity that affects the aggressiveness and progression of NB through transcriptional upregulation of MYCN.

SummaryA suite of newly discovered sucrose transporter genes, PsSUF1, PsSUF4, PvSUT1 and PvSUF1, were isolated from the coats of developing pea (Pisum sativum L.) and bean (Phaseolus vulgaris L.) seeds. Sequence analysis indicated that deduced proteins encoded by PsSUF1, PvSUT1 and PvSUF1 clustered in a separate sub-group under sucrose transporter Clade I, whereas the deduced protein encoded by PsSUF4 clustered in Clade II. When expressed in yeast, these genes were shown to encode sucrose transporters with apparent Michaelis Menten constant (K m ) values ranging from 8.9 to 99.8 mM. PvSUT1 exhibited functional characteristics of a sucrose/H þ symporter. In contrast, PsSUF1, PvSUF1 and PsSUF4 supported the pH-and energy independent transport of sucrose that was shown to be bi-directional. These transport properties, together with that of counter transport, indicated that PsSUF1, PvSUF1 and PsSUF4 function as carriers that support the facilitated diffusion of sucrose. Carrier function was unaffected by diethylpyrocarbonate and by maltose competition, suggesting that the sucrose binding sites of these transporters differed from those of known sucrose/H þ symporters. All sucrose transporters were expressed throughout the plant and, of greatest interest, were coexpressed in cells considered responsible for sucrose efflux from seed coats. The possible roles played by the novel facilitators in sucrose efflux from seed coats are discussed.

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Heparanase (HPSE) is the endogenous endoglycosidase that degrades heparan sulfate proteoglycans and promotes the tumor growth, invasion, metastasis and angiogenesis. Our previous studies have shown that HPSE is highly expressed in neuroblastoma (NB), the most common extracranial solid tumor in childhood. However, the underlying regulatory mechanisms remain largely unknown. In this study, we identified one binding site of microRNA-558 (miR-558) within the HPSE promoter. In NB tissues and cell lines, miR-558 was up-regulated and positively correlated with HPSE expression. Gain- and loss-of-function studies demonstrated that miR-558 facilitated the transcript and protein levels of HPSE and its downstream gene, vascular endothelial growth factor, in NB cell lines. In addition, miR-558 enhanced the promoter activities of HPSE, and these effects were abolished by the mutation of the miR-558-binding site. Mechanistically, miR-558 induced the enrichment of the active epigenetic marker and RNA polymerase II on the HPSE promoter in NB cells in an Argonaute 1-dependent manner, which was abolished by repressing the miR-558-promoter interaction. Knockdown of endogenous miR-558 decreased the growth, invasion, metastasis and angiogenesis of NB cells in vitro and in vivo. In contrast, over-expression of miR-558 promoted the growth, invasion, metastasis and angiogenesis of SH-SY5Y and SK-N-SH cells. Restoration of HPSE expression prevented the NB cells from changes in these biological features induced by knockdown or over-expression of miR-558. These data indicate that miR-558 induces the transcriptional activation of HPSE via the binding site within promoter, thus facilitating the tumorigenesis and aggressiveness of NB.

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BackgroundRecent studies have demonstrated that cellular energy is a key factor switching on ripening and senescence of fruit. However, the factors that influence fruit energy status remain largely unknown.ResultsHPLC profiling showed that ATP abundance increased significantly in developing preharvest litchi fruit and was strongly correlated with fruit fresh weight. In contrast, ATP levels declined significantly during postharvest fruit senescence and were correlated with the decrease in the proportion of edible fruit. The five gene transcripts isolated from the litchi fruit pericarp were highly expressed in vegetative tissues and peaked at 70 days after flowering (DAF) consistent with fruit ADP concentrations, except for uncoupling mitochondrial protein 1 (UCP1), which was predominantly expressed in the root, and ATP synthase beta subunit (AtpB), which was up-regulated significantly before harvest and peaked 2 days after storage. These results indicated that the color-breaker stage at 70 DAF and 2 days after storage may be key turning points in fruit energy metabolism. Transcript abundance of alternative oxidase 1 (AOX1) increased after 2 days of storage to significantly higher levels than those of LcAtpB, and was down-regulated significantly by exogenous ATP. ATP supplementation had no significant effect on transcript abundance of ADP/ATP carrier 1 (AAC1) and slowed the changes in sucrose non-fermenting-1-related kinase 2 (SnRK2) expression, but maintained ATP and energy charge levels, which were correlated with delayed senescence.ConclusionsOur results suggest that senescence of litchi fruit is closely related with energy. A surge of LcAtpB expression marked the beginning of fruit senescence. The findings may provide a new strategy to extend fruit shelf life by regulating its energy level.

Mycotoxins are small toxic chemical products formed as the secondary metabolites by fungi that readily contaminate foods with toxins in the field or after harvest. The presence of mycotoxins, such as aflatoxins, ochratoxin A, and patulin, in fruits and their processed products is of high concern for human health due to their properties to induce severe acute and chronic toxicity at low-dose levels. Currently, a broad range of detection techniques used for practical analysis and detection of a wide spectrum of mycotoxins are available. Many analytical methods have been developed for the determination of each group of these mycotoxins in different food matrices, but new methods are still required to achieve higher sensitivity and address other challenges that are posed by these mycotoxins. Effective technologies are needed to reduce or even eliminate the presence of the mycotoxins in fruits and their processed products. Preventive measures aimed at the inhibition of mycotoxin formation in fruits and their processed products are the most effective approach. Detoxification of mycotoxins by different physical, chemical, and biological methods are less effective and sometimes restricted because of concerns of safety, possible losses in nutritional quality of the treated commodities and cost implications. This article reviewed the available information on the major mycotoxins found in foods and feeds, with an emphasis of fruits and their processed products, and the analytical methods used for their determination. Based on the current knowledge, the major strategies to prevent or even eliminate the presence of the mycotoxins in fruits and their processed products were proposed.