In both prokaryotes and eukaryotes nonsense mutations in a gene can enhance the decay rate of the mRNA transcribed from that gene, a phenomenon described as nonsense-mediated mRNA decay. In yeast, the products of the UPF1 and UPF3 genes are required for this decay pathway, and in this report we focus on the identification and characterization of additional factors required for rapid decay of nonsense-containing mRNAs. We present evidence that the product of the UPF2 gene is a new factor involved in this decay pathway. Mutation of the UPF2 gene or deletion of it from the chromosome resulted in stabilization of nonsense-containing mRNAs, whereas the decay of wild-type transcripts was not affected. The UPF2 gene was isolated, and its transcript was characterized. Our results demonstrate that the UPF2 gene encodes a putative 126.7-kD protein with an acidic region at its carboxyl terminus (-D-E)n found in many nucleolar and transcriptional activator proteins. The UPF2 transcript is 3600 nucleotides in length and contains an intron near its 5' end. The UPF2 gene is dispensable for vegetative growth, but upf2A strains were found to be more sensitive to the translational elongation inhibitor cycloheximide than UPF2 § A genetic analysis of other alleles proposed to be involved in nonsense-mediated mRNA decay revealed that the UPF2 gene is allelic to the previously identified sual allele, a suppressor of an out-of-frame ATG insertion shown previously to reduce translational initiation from the normal ATG of the CYC1 gene. In addition, we demonstrate that another suppressor of this cycl mutation, sua6, is allelic to upf3, a previously identified lesion involved in nonsense-mediated mRNA decay.
Edited by Tamas Dalmay Keywords:MicroRNA-93 PTEN Drug resistance Cisplatin Human ovarian cancer a b s t r a c tThe mechanisms underlying ovarian cancer cell resistance to cisplatin (CDDP) are not fully understood. MicroRNAs (miRNAs) play important roles in tumorigenesis and drug resistance. In this paper, we utilized microRNA array and real-time PCR to show that miR-93 is significantly up-regulated in cisplatin-resistant ovarian cancer cells. In vitro assays show that over-expression and knock-down of miR-93 regulate apoptotic activity, and thereby cisplatin chemosensitivity, in ovarian cells. Furthermore, we found that miR-93 can directly target PTEN, and participates in the regulation of the AKT signaling pathway. MiR-93 inversely correlates with PTEN expression in CDDP-resistant and sensitive human ovarian cancer tissues. These results may have implications for therapeutic strategies aiming to overcome ovarian cancer cell resistance to cisplatin.
The polygenic nature of complex psychiatric disorders suggests a common pathway that may be involved in the down-regulation of multiple genes through an epigenetic mechanism. To investigate the role of methylation in down-regulating the expression of mRNAs that may be associated with the schizophrenia phenotype, we have adopted a cell-culture model amenable to this line of investigation. We have administered methionine (2 mM) to primary cultures of cortical neurons prepared from embryonic day 16 mice and show that this treatment down-regulated reelin and glutamic acid decarboxylase 67 (GAD67) mRNA expression but not that corresponding to neuron-specific enolase mRNA. Moreover, methionine increased methylation of the reelin promoter, suggesting a possible mechanism for the observed change. These cultures contain a mixed population of neurons and glia. Approximately 83% of the neurons are GABAergic based on GAD immunoreactivity, and these neurons coexpress high levels of reelin and DNA methyltransferase (Dnmt) 1 immunoreactivity. To examine whether Dnmt1 regulates reelin gene expression, we used an antisense approach to reduce (knock down) Dnmt1 expression. The reduced Dnmt1 mRNA and protein were accompanied by increased reelin mRNA expression. More importantly, the Dnmt1 knockdown blocked the methionine-induced reelin and GAD67 mRNA downregulation. These data support the hypothesis that the reduced amounts of reelin and GAD67 mRNAs documented in postmortem schizophrenia brain may be the consequence of a Dnmt1-mediated hypermethylation of the corresponding promoters.epigenetics ͉ gene expression ͉ methylation ͉ schizophrenia
BackgroundPancreatic cancer is one of the most lethal cancers worldwide. The aim of this study was to determine the expression pattern, clinical significance, and biological functions of Wnt5a in pancreatic cancer.MethodsImmunohistochemistry was performed to examine Wnt5a expression in 134 surgically resected pancreatic adenocarcinoma and adjacent normal pancreatic tissues. Associations of Wnt5a expression with clinicopathological factors and cancer-specific survival were analyzed. The effects of Wnt5a overexpression or silencing on the invasiveness and epithelial-to-mesenchymal transition (EMT) of pancreatic cancer cells were studied. Silencing of β-catenin by small interfering RNA was done to determine its role in the Wnt5a-mediated tumor phenotype.ResultsThe percentage of Wnt5a positive expression showed a bell-shaped pattern in pancreatic cancer tissues, peaking in well-differentiated carcinomas. The median cancer-specific survival was comparable between patients with positive versus negative expression of Wnt5a. Overexpression of Wnt5a promoted the migration and invasion of pancreatic cancer cells, whereas Wnt5a depletion had an inhibitory effect. In an orthotopic pancreatic cancer mouse model, Wnt5a overexpression resulted in increased invasiveness and metastasis, coupled with induction of EMT in tumor cells. Treatment with recombinant Wnt5a elevated the nuclear β-catenin level in pancreatic cancer cells, without altering the Ror2 expression. Targeted reduction of β-catenin antagonized exogenous Wnt5a-induced EMT and invasiveness in pancreatic cancer cells.ConclusionUpregulation of Wnt5a promotes EMT and metastasis in pancreatic cancer models, which involves activation of β-catenin-dependent canonical Wnt signaling. These findings warrant further investigation of the clinical relevance of Wnt5 upregulation in pancreatic cancer.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.