13 research outputs found
Two different snoRNAs are encoded in introns of amphibian and human L1 ribosomal protein genes
No full textWe previously reported that the third intron of the X.laevis L1 ribosomal protein gene encodes for a snoRNA called U16. Here we show that four different introns of the same gene contain another previously uncharacterized snoRNA (U18) which is associated with fibrillarin in the nucleolus and which originates by processing of the pre-mRNA. The pathway of U18 RNA release from the pre-mRNA is the same as the one described for U16: primary endonucleolytic cleavages upstream and downstream of the U18 coding region produce a pre-U18 RNA which is subsequently trimmed to the mature form. Both the gene organization and processing of U18 are conserved in the corresponding genes of X.tropicalis and H.sapiens. The L1 gene thus has a composite structure, highly conserved in evolution, in which sequences coding for a ribosomal protein are intermingled with sequences coding for two different snoRNAs. The nucleolar localization of these different components suggests some common function on ribosome biosynthesis
Gli family transcription factors are drivers of patupilone resistance in ovarian cancer
No full textEpothilones constitute a novel class of antitubulin agents that are active in patients who relapse after treatment with other chemotherapeutics. This study investigated the molecular mechanisms leading to the onset of epothilone-B (patupilone) resistance in ovarian cancer. Results demonstrated that the Gli family of transcription factors was overexpressed in resistant cells and that treatment with a specific Gli1 inhibitor (GANT58) made cells more susceptible to treatment, partially reversing drug resistance. We also demonstrated that Gli1 knockdown halted growth in resistant cells that were exposed to patupilone, confirming that Gli1 is capable of directly mediating epothilone-B resistance. Another observation from our research was that patupilone-resistant cells produced HGF and acquired characteristics of a mesenchymal phenotype. However, HGF silencing alone was not capable of converting the drug-resistant phenotype to a susceptible one, and in this case we demonstrated that Gli1 overexpression led to an increase in HGF, establishing a functional link between Gli1 and HGF. These results demonstrated that Gli1 played a key role in driving resistance to patupilone, suggesting that the combination of epothilones and Gli1-targeted agents could be exploited to improve outcomes in ovarian cancer patients resistant to standard treatments
SELF-CLEAVING MOTIFS ARE FOUND IN CLOSE PROXIMITY TO THE SITES UTILIZED FOR U16 SNORNA PROCESSING
No full textA class of small nucleolar RNAs (snoRNAs) is encoded in introns of protein-coding genes. The U16 snoRNA belongs to this class; it is encoded in the third intron of the Xenopus laevis (Xl) L1 ribosomal protein encoding gene and is released from the pre-mRNA by processing both in vivo and in vitro systems. In this paper, we show that in close proximity to the U16 snoRNA processing sites, sequences displaying self-cleaving activity are present. These elements are conserved in the two copies of the Xl L1 and in the single copy of the X. tropicalis L1. The catalytic activity corresponds to that already described for the minimal hairpin ribozyme [Dange et al., Science 242 (1990) 585-588]; it is Mn2+-dependent, produces 2'-3' cyclic phosphate and 5'-OH termini and comprises an essential GAAA element. Here we show that the 2'-OH group of the G residue is essential for catalysis
MiR-200c and HuR in ovarian cancer
No full textBACKGROUND: MicroRNAs in solid malignancies can behave as predictors of either good or poor outcome. This is the case with members of the miR-200 family, which are the primary regulators of the epithelial to mesenchymal transition and have been reported to act as both oncogenes and tumor suppressors. This study assessed the role of miR-200c as regulator of class III β-tubulin (TUBB3), a factor associated with drug-resistance and poor prognosis in ovarian cancer.
METHODS: Expression of miR-200c was assessed in a panel of ovarian cancer cell lines with inherent or acquired drug-resistance. Stable overexpression of miR-200c was obtained in A2780 and Hey cell lines. Crosslinking-coupled affinity purification method and ribonucleic-immunoprecipitation assay were used to characterise the complexes between miR-200c, HuR and 3'UTR region of TUBB3 mRNA. Nanofluidic technology and immunohistochemistry were used to analyze the expression of HuR, TUBB3 and miR-200c in 220 ovarian cancer patients.
RESULTS: In a panel of ovarian adenocarcinoma cell lines, we observed a direct correlation between miR-200c expression and chemoresistance. In A2780 cells miR-200c targeted TUBB3 3'UTR, while a positive correlation was observed between miR-200c and TUBB3 expression in most of the other cell lines. Through the analysis of 3'UTR-associated complexes, we found that the miR-200c can increase the association of the RNA binding protein HuR with TUBB3 mRNA, whereas HuR binding enhanced TUBB3 mRNA translation. Most importantly, in our analysis on 220 ovarian cancer patients we observed that overexpression of miR-200c correlated with poor or good outcome depending on the cellular localization of HuR.
CONCLUSION: This study suggests a model for the combined regulatory activity of miR-200c and HuR on TUBB3 expression in ovarian cancer. When HuR is nuclear, high expression of miR-200c inhibits TUBB3 expression and results in a good prognosis, whereas when HuR occurs in cytoplasm, the same miRNA enhances TUBB3 expression and produces a poor outcome. These findings reveal the usefulness of multidimensional analysis in the investigation of the prognostic role of miRNA expression
Lack of stimulatory activity of a Phytoestrogen-containing soy extract on the growth of breast cancer tumors in mice
No full textHuR regulates beta-tubulin isotype expression in ovarian cancer
No full textThe supply of oxygen and nutrients to solid tumors is inefficient because cancer tissues have an inadequate number of microvessels, thus inducing the selective growth of the most aggressive cancer cells. This explains why many of the factors underlying a poor prognosis are induced in hypoxic/hypoglycemic conditions. Among these factors, a prominent role in several solid tumors is played by the class III beta-tubulin gene (TUBB3). The study described here reveals that glucose deprivation enhances TUBB3 expression at both the gene and protein levels in A2780 ovarian cancer cells. In silico analysis of TUBB3 mRNA sequence predicted a putative binding site for the RNA-binding protein Hu antigen (HuR) in the 3' flanking untranslated region. A hypoglycemic-dependent engagement of this site was shown using RNA pull-down and ribonucleoimmunoprecipitation techniques. Thereafter, HuR gene silencing revealed that TUBB3 translation is HuR dependent in hypoglycemia because HuR silencing inhibited the entry of TUBB3 mRNA into cytoskeletal and free polysomes. Finally, the clinical value of this finding was assessed in a clinical cohort of 46 ovarian cancer patients in whom it was found that HuR cytoplasmic staining was associated with high levels of TUBB3 and poor surviva
Hypoxia induces class III beta-tubulin gene expression by HIF-1α binding to its 3' flanking region
No full textAbstract 1957: MiR-200c can mediate either poor or good outcome in ovarian cancer depending on HuR localization in the cell.
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