Biomedical subjects

Yvan De Launoit

Publications and source records attributed to Yvan De Launoit.

5 recordsLinked to original sources

PubMed2006

ASK-1 (apoptosis signal-regulating kinase 1) is a direct E2F target gene.

In the present study, we show that E2Fs (E2 promoter-binding factors) regulate the expression of ASK-1 (apoptosis signal-regulating kinase 1), which encodes a mitogen-activated protein kinase kinase kinase, also known as MAP3K5. Its mRNA expression is cell-cycle-regulated in human T98G cells released from serum starvation. Moreover, overexpression and RNA interference experiments support the requirement of endogenous E2F/DP (E2F dimerization partner) activity for ASK-1 expression. Characterization of the human ASK-1 promoter demonstrates that the -95/+11 region is critical for E2F-mediated up-regulation. Chromatin immunoprecipitation assays show that E2F1-E2F4 are bound in vivo to the ASK-1 promoter in cycling cells, probably through a non-consensus E2F-binding site located 12 bp upstream of the transcription start site. Mutation of this site completely abolishes the ASK-1 promoter response to E2Fs as well as the E2F1 binding in electrophoretic mobility-shift experiments. Our results indicate that E2Fs modulate the expression of ASK-1 and suggest that some of the cellular functions of ASK-1 may be under the control of E2F transcription factors. Moreover, the up-regulation of ASK-1 may also favour the p53-independent E2F1 apoptotic activity.

Binding Sites↗

PubMed2004

The NRF-1/alpha-PAL transcription factor regulates human E2F6 promoter activity.

E2F6 is widely expressed in human tissues and cell lines. Recent studies have demonstrated its involvement in developmental patterning and in the regulation of various genes implicated in chromatin remodelling. Despite a growing number of studies, nothing is really known concerning the E2F6 expression regulation. To understand how cells control E2F6 expression, we analysed the activity of the previously cloned promoter region of the human E2F6 gene. DNase I footprinting, gel electrophoreticmobility shift, transient transfection and site-directed mutagenesis experiments allowed the identification of two functional NRF-1/alpha-PAL (nuclear respiratory factor-1/alpha-palindrome-binding protein)-binding sites within the human E2F6 core promoter region, which are conserved in the mouse and rat E2F6 promoter region. Moreover, ChIP (chromatin immunoprecipitation) analysis demonstrated that overexpressed NRF-1/alpha-PAL is associated in vivo with the E2F6 promoter. Furthermore, overexpression of full-length NRF-1/alpha-PAL enhanced E2F6 promoter activity, whereas expression of its dominant-negative form reduced the promoter activity. Our results indicate that NRF-1/alpha-PAL is implicated in the regulation of basal E2F6 gene expression.

Animals↗

PubMed2004

Human E2F6 is alternatively spliced to generate multiple protein isoforms.

E2F6 protein belongs to the family of the E2F transcription factors. Here, we showed that the human E2F6 gene contains nine exons distributed along 20.4kbp of genomic DNA on chromosome 2 leading to the transcription of six alternatively spliced E2F6 mRNAs that encode four different E2F6 proteins. Moreover, we identified an E2F6 pseudogene localized on chromosome 22 completely spliced and devoid of exons 2, 3, and 4, and part of exons 1 and 5. Definition of the transcriptional initiation site and sequence analysis show that the gene contains a TATA less, CAAT less, GC-rich promoter with multiple transcription start sites. Regulatory elements necessary for basal transcription reside within a 134bp fragment as determined by transient transfection experiments.

Alternative Splicing↗

PubMed2003

Potentiation of tumor necrosis factor-induced NF-kappa B activation by deacetylase inhibitors is associated with a delayed cytoplasmic reappearance of I kappa B alpha.

Previous studies have implicated acetylases and deacetylases in regulating the transcriptional activity of NF-kappa B. Here, we show that inhibitors of deacetylases such as trichostatin A (TSA) and sodium butyrate (NaBut) potentiated TNF-induced expression of several natural NF-kappa B-driven promoters. This transcriptional synergism observed between TNF and TSA (or NaBut) required intact kappa B sites in all promoters tested and was biologically relevant as demonstrated by RNase protection on two instances of endogenous NF-kappa B-regulated gene transcription. Importantly, TSA prolonged both TNF-induced DNA-binding activity and the presence of NF-kappa B in the nucleus. We showed that the p65 subunit of NF-kappa B was acetylated in vivo. However, this acetylation was weak, suggesting that other mechanisms could be implicated in the potentiated binding and transactivation activities of NF-kappa B after TNF plus TSA versus TNF treatment. Western blot and immunofluorescence confocal microscopy experiments revealed a delay in the cytoplasmic reappearance of the I kappa B alpha inhibitor that correlated temporally with the prolonged intranuclear binding and presence of NF-kappa B. This delay was due neither to a defect in I kappa B alpha mRNA production nor to a nuclear retention of I kappa B alpha but was rather due to a persistent proteasome-mediated degradation of I kappa B alpha. A prolongation of I kappa B kinase activity could explain, at least partially, the delayed I kappa B alpha cytoplasmic reappearance observed in presence of TNF plus TSA.

Animals↗

PubMed2003

Inhibition of JNK by HGF/SF prevents apoptosis induced by TNF-alpha.

We investigated whether repression of JNK by hepatocyte growth factor/scatter factor (HGF/SF) in MDCK epithelial cells is linked to its ability to protect cells from apoptosis. To this purpose, cells were treated by TNF-alpha, a well-known inducer of JNK and of cell death, and the effects of HGF/SF were investigated under these conditions. We identified repression of JNK as a signaling target of HGF/SF for protection against TNF-alpha-induced cell death. This effect of HGF/SF occurs via the activation of the PI3K and MEK1 pathways.

Animals↗