p21Waf1 expression is regulated by nuclear intermediate filament vimentin in neuroblastoma

<p>Abstract</p> <p>Background</p> <p>Human neuroblastoma (NB) cell lines may present with either one of the so-called S-and N-subtypes. We have previously reported a strong correlation between protein expression levels of vimentin, an S-subtype marker, and the p21^Waf1cyclin-dependent kinase inhibitor. We here investigated whether this correlation extend to the mRNA level in NB cell lines as well as in patients' tumors. We also further explored the relationship between expression of vimentin and p21, by asking whether vimentin could regulate p21 expression.</p> <p>Methods</p> <p>Vimentin and p21 mRNA levels in NB cell lines as well as in patients' tumors (<it>n </it>= 77) were quantified using Q-PCR. Q-PCR data obtained from tumors of high risk NB patients (<it>n </it>= 40) were analyzed in relation with the overall survival using the Log-rank Kaplan-Meier estimation. siRNA-mediated depletion or overexpression of vimentin in highly or low expressing vimentin cell lines, respectively, followed by protein expression and promoter activation assays were used to assess the role of vimentin in modulating p21 expression.</p> <p>Results</p> <p>We extend the significant correlation between vimentin and p21 expression to the mRNA level in NB cell lines as well as in patients' tumors. Overall survival analysis from Q-PCR data obtained from tumors of high risk patients suggests that lower levels of p21 expression could be associated with a poorer outcome. Our data additionally indicate that the correlation observed between p21 and vimentin expression levels results from p21 transcriptional activity being regulated by vimentin. Indeed, downregulating vimentin resulted in a significant decrease in p21 mRNA and protein expression as well as in p21 promoter activity. Conversely, overexpressing vimentin triggered an increase in p21 promoter activity in cells with a nuclear expression of vimentin.</p> <p>Conclusion</p> <p>Our results suggest that p21 mRNA tumor expression level could represent a refined prognostic factor for high risk NB patients. Our data also show that vimentin regulates p21 transcription; this is the first demonstration of a gene regulating function for this type III-intermediate filament.</p

p73α isoforms drive opposite transcriptional and post-transcriptional regulation of MYCN expression in neuroblastoma cells

MYCN activation, mainly by gene amplification, is one of the most frequent molecular events in neuroblastoma (NB) oncogenesis, and is associated with increased malignancy and decreased neuronal differentiation propensity. The frequency of concomitant loss of heterozygosity at the 1p36.3 locus, which harbours the p53 anti-oncogene homologue TP73, indicates that MYCN and p73 alterations may cooperate in the pathogenesis of NB. We have previously shown that p73 isoforms are deregulated in NB tumours and that TAp73 co-operates synergistically with p53 for apoptosis of NB cells, whereas ΔNp73 activates the expression of neuronal differentiation genes such as BTG2. Herein, using both ectopic expression and RNA interference-mediated silencing of p73 in MYCN amplified NB cells, we show that p73α isoforms inhibit MYCN expression at both transcript and protein levels, in spite of transactivator effects on MYCN promoter. To explain this paradox, we found that TAp73α exerts negative post-transcriptional effects leading to reduced MYCN mRNA stability. RNA immunoprecipitation experiments suggest that this dominant inhibitory post-transcriptional effect could be due to an interaction between the p73 protein and MYCN mRNA, a hypothesis also raised for the regulation of certain genes by the p53 protein

Role of yeast and human FACT in DNA replication and genomic stability

Póster presentado en EMBO Workshop on Recombination Mechanism and Genome Instability, celebrado en Jeréz de la Frontera (España) del 21 al 25 de mayo de 2012Peer Reviewe

Telomere regulation during ageing and tumorigenesis of the grey mouse lemur

International audienc