Down-regulation of STAT3 expression by vector-based small interfering RNA inhibits pancreatic cancer growth

AIM:To evaluate the effect of RNA interference (RNAi) mediated silence of signal transduction and activation of transcription (STAT)3 on the growth of human pancreatic cancer cells both in vitro and in vivo.METHODS:STAT3 specific shRNA was used to silence the expression of STAT3 in pancreatic cancer cell line SW1990.The anti-growth effects of RNAi against STAT3 were studied in vitro and in experimental cancer xenografts in nude mice.The potential pathways involved in STAT3 signaling were detected using reverse transcription polymerase chain reaction and western blotting.RESULTS:The expression of the STAT3 was inhibited using RNAi in SW1990 cells.RNAi against STAT3 inhibited cell proliferation,induced cell apoptosis and significantly reduced the levels of CyclinD1 and Bcl-xL when compared with parental and control vector-transfected cells.In vivo experiments showed that RNAi against STAT3 inhibited the tumorigenicity of SW1990 cells and significantly suppressed tumor growth when it was directly injected into tumors.CONCLUSION:STAT3 signaling pathway plays an important role in the progression of pancreatic cancer,and silence of STAT3 gene using RNAi technique may be a novel therapeutic option for treatment of pancreatic cancer.

Genome-Wide Identification and Characterization of the <i>Dof</i>Transcription Factor Gene Family in <i>Phaseolus vulgaris</i>L.

The Dof (DNA-binding with one finger) proteins are a class of plant-specific transcription factors that can trigger several processes involved in plant growth and development, as well as in stress responses. Here, we performed a systematic bioinformatics analysis to characterize all Dof genes in common bean, which included analysis of the genome sequence, conserved protein domains, chromosomal locations, subcellular locations, phylogenetic relationships, gene duplications, and gene expression profiles in different tissues. Bioinformatics analysis revealed 36 putative genes related to PvDof that were classified into seven subfamilies (A, B1, B2, C1, C2, D1, and, D2) by comparative phylogenetic analysis. Based on our genome duplication analysis, a total of 36 genes were found to be distributed on all 11 chromosomes, and they expanded through gene duplication in tandem, suggesting the involvement of segmental duplication events in the evolutionary process. Synteny events and phylogenetic comparisons of the Dof proteins of common bean with those of A. thaliana, O. sativa, and G. max L. led to the identification of several orthologous and paralogous genes, which provided further insight into the diversity of the evolutionary characteristics of genes of this family in other plant species. Expression profiles revealed that most of the PvDof genes were expressed in different tissues, indicating that PvDof genes may be involved in various physiological functions during plant development. The results of this study provide additional information and potential biotechnological resources for further understanding the molecular basis of this gene family and consequently improvement of common bean crops.

Regulation of MYB and bHLH Transcription Factors： A Glance at the Protein Level

In complex, constantly changing environments, plants have developed astonishing survival strategies. These elaborated strategies rely on rapid and precise gene regulation mediated by transcription factors （TFs）. TFs represent a large fraction of plant genomes and among them, MYBs and basic helix-loop-helix （bHLHs） have unique inherent properties specific to plants. Proteins of these two TF families can act as homo- or heterodimers, associate with proteins from other protein families, or form MYB/bHLH complexes to regulate distinct cellular processes. The ability of MYBs and bHLHs to interact with multiple protein part- ners has evolved to keep up with the increased metabolic complexity of multi-cellular organisms. Associ- ation and disassociation of dynamic TF complexes in response to developmental and environmental cues are controlled through a plethora of regulatory mechanisms specifically modulating TF activity. Regulation of TFs at the protein level is critical for efficient and precise control of their activity, and thus provides the mechanistic basis for a rapid on-and-off switch of TF activity. In this review, examples of post-translational modifications, protein-protein interactions, and subcellular mobilization of TFs are discussed with regard to the relevance of these regulatory mechanisms for the specific activation of MYBs and bHLHs in response to a given environmental stimulus.

Influence of DNA methylation on transgene expression

DNA methylation plays an important role in gene expression in eukaryote. But DNA methylation of transgene usually leads to target gene silencing in plant genetic engineering. In this research, reporter gene β-glu-curonidase (GUS) gene (uidA) was introduced into tobaccos via Agrobacterium-mediated transformation method, and the foreign uidA gene became inactive in some transgenic tobaccos. No mRNA of uidA was detected in these plants by Northern blotting analysis, and DNA methylation of promoter region was found. The results indicated that gene silencing might be caused by DNA methylation of promoter.

Natural variation in the NAC transcription factor NONRIPENING contributes to melon fruit ripening

ThThe NAC transcription factor NONRIPENING(NOR)is a master regulator of climacteric fruit ripening.Melon(Cucumis melo L.)has climacteric and nonclimacteric fruit ripening varieties and is an ideal model to study fruit ripening.Two natural CmNAC-NOR variants,the climacteric haplotype CmNAC-NOR^(S,N) and the non-climacteric haplotype CmNAC-NOR^(A,S),have effects on fruit ripening;however,their regulatory mechanisms have not been elucidated.Here,we report that a natural mutation in the transcriptional activation domain of CmNAC-NORS,Ncontributes to climacteric melon fruit ripening.CmNAC-NOR knockout in the climacteric-type melon cultivar“BYJH”completely inhibited fruit ripening,while ripening was delayed by 5-8 d in heterozygous cmnac-nor mutant fruits.CmN AC-NOR directly activated carotenoid,ethylene,and abscisic acid biosynthetic genes to promote fruit coloration and ripening.Furthermore,CmNAC-NOR mediated the transcription of the“CmNAC-NOR-CmNAC73-CmCWINV2”module to enhance flesh sweetness.The transcriptional activation activity of the climacteric haplotype CmNAC-NORS,Non these target genes was significantly higher than that of the nonclimacteric haplotype CmNAC-NOR^(A,S).Moreover,CmNAC-NORS,Ncomplementation fully rescued the non-ripening phenotype of the tomato(Solanum lycopersicum)cr-nor mutant,while CmNAC-NOR^(A,S) did not.Our results provide insight into the molecular mechanism of climacteric and non-climacteric fruit ripening in melon.

Prediction and Validation of Promoters Involved in the Abscisic Acid Response in Physcomitrella patens

Detection of cis-regulatory elements, such as transcription factor binding sites （TFBS）, through utilization of ortholog conservation is possible only if genomic data from closely related organisms are available. An alternative approach is the detection of TFBS based on their overrepresentation in promoters of co-regulated genes. However, this approach usually suffers from a high rate of false-positive prediction. Here, we have conducted a case study using promoters of genes known to be strongly induced by the phytohormone abscisic acid （ABA） in the model plant Physcomitrella patens, a moss. Putative TFBS were detected using three de novo motif detection tools in a strict consensus approach. The resulting motifs were validated using data from microarray expression profiling and were able to predict ABA-induced genes with high specificity （90.48%） at mediocre sensitivity （33.33%）. In addition, 27 genes predicted to contain ABA-responsive TFBS were validated using real-time PCR. Here, a total of 37% of the genes could be shown to be induced upon ABA treatment, while 70% were found to be regulated by ABA. We conclude that the consensus approach for motif detection using coregulation information can be used to identify genes that are regulated under a given stimulus. In terms of evolution, we find that the ABA response has apparently been conserved since the first land plants on the level of families involved in transcriptional regulation.