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Biomedical subjects

D Stéhelin

Publications and source records attributed to D Stéhelin.

At least 37 records · Page 2Linked to original sources
PubMed1995

Increased T-cell apoptosis and terminal B-cell differentiation induced by inactivation of the Ets-1 proto-oncogene.

The Ets-1 proto-oncogene is a member of a transcription factor family characterized by homology to the v-ets oncogene. In adult mice, Ets-1 is expressed predominantly in lymphoid cells where it has been implicated in regulating transcription of lymphocyte-specific genes. Following T-cell activation, the specific DNA binding activity of Ets-1 is inactivated by transient phosphorylation, suggesting a function in the transition from the resting to activated state. Ets-1 has also been suggested to cooperate with the AP-1 transcription factor complex to mediate cellular growth factor responses. Here we show, by using RAG-2-deficient blastocyst complementation, that Ets-1 deficiency has dramatic, but different, effects on development and function of T- and B-lineage cells. Ets-1-deficient T cells were present in reduced numbers and were highly susceptible to cell death in vitro. In contrast, Ets-1-deficient B cells were present in normal numbers but a large proportion were IgM plasma cells. Our data demonstrate that Ets-1 is essential for maintenance of the normal pool of resting T- and B-lineage cells.

Animals↗
PubMed1995

Molecular cloning of a novel widely expressed human 80 kDa 17 beta-hydroxysteroid dehydrogenase IV.

Reactions of oestrogens and androgens at position C-17 are catalysed by 17 beta-hydroxysteroid dehydrogenases (17 beta-HSDs). Cloning of the cDNA of a novel human 17 beta-HSD IV and expression of its mRNA are described. A probe derived from the recently discovered porcine 17 beta-oestradiol dehydrogenase (17 beta-EDH) was used to isolate a 2.6 kb human cDNA encoding a continuous protein of 736 amino acids of high (84%) similarity to the porcine 17 beta-EDH. The calculated molecular mass of the human enzyme is 79,595 Da. Other sequence similarities shared by the two enzymes are: an N-terminal sequence which is similar to that of members of the short-chain alcohol dehydrogenase family; amino acids 343-607 which are similar to the C-terminal domains of a trifunctional Candida tropicalis enzyme and the FOX2 gene product of Saccharomyces cerevisiae; amino acids 596-736 which are similar to human sterol carrier protein 2. The previously cloned human 17 beta-HSD I, II and III are less than 25% identical with 17 beta-HSD IV. mRNA for HSD IV is a single species of 3.0 kb, present in many tissues with highest concentrations in liver, heart, prostate and testes. When over-expressed in mammalian cells, the human 17 beta-HSD IV enzyme displays a specific unidirectional oxidative 17 beta-HSD activity.

17-Hydroxysteroid Dehydrogenases↗
PubMed1995

Molecular characterization of the ets-related human transcription factor ER81.

The PEA3 group is a homogeneous group of the ets transcription factor family and is composed of three known members, PEA3, ERM and ER81, which, on the amino acid (AA) level, are more than 95% identical within the DNA-binding domain (the Ets domain), more than 85% within a 32 AA domain (the acidic domain) localized in the amino-terminus and almost 50% identical overall. By screening a human kidney cDNA library with a specific probe obtained from mouse ER81, we isolated two clones of 1.6 and 1.5 kb in length encoding a 458 AA open reading frame. When compared to mouse ER81, the present human ER81 lacks the last 13 AA of the acidic domain and the 5 AA contiguous to the carboxy-terminal part of the acidic domain. Of the 458 AA of the human ER81 protein, 97% are identical to mouse ER81. Gel shift analysis indicates that the full-length human ER81 protein is able to bind specifically to an oligonucleotide containing the binding sites recognized by most of the Ets proteins. By transient expression in RK13 mammalian cells, human ER81 protein transactivated a reporter plasmid containing Ets binding sites, indicating that this molecule is a bonafide transcriptional activator, while by expression in Cos-1 transfected cells, we detected the presence of human ER81 protein in the nucleus using immunocytochemistry. In human tissues, ER81 mRNA is very highly expressed in brain, highly expressed in testis, lung and heart, moderately in spleen, small intestine, pancreas and colon, weakly in liver, prostate and thymus, very weakly in skeletal muscle, kidney and ovary and not in placenta and peripheral blood leukocytes. Analysis of human solid or haematopoietic tumour cell lines showed that most of them did not express ER81 detectably. Database searches revealed that ETV1 mRNA is highly similar to human ER81 described here, although it contains the full-length acidic domain present in mouse ER81. By screening a genomic DNA library, we characterized the intron-exon junction within the acidic domain of human ER81 and we showed that this junction corresponds to the site where the remaining AA of the acidic domain of ETV1 or mouse ER81 are inserted.

Amino Acid Sequence↗
PubMed1995

Invasive tumors induce c-ets1 transcription factor expression in adjacent stroma.

The stroma reaction plays a central role in tumor growth, invasion and metastasis. Tumor growth is dependent on angiogenesis and requires the vascular supply provided by new capillary blood vessels of the stroma. The expression of the gene encoding the transcription factor c-ets1 is localized within fibroblasts and endothelial cells of the stromal compartment. This expression correlates with the accumulation of transcripts for potential target genes such as collagenase I and stromelysin I in stromal fibroblasts surrounding malignant cells in invasive tumors. We suggest that c-Ets1 protein might regulate the transcription of the genes coding for matrix-degrading proteases necessary for both angiogenesis and tumor invasion.

Angiogenesis Inducing Agents↗
PubMed1995

High alpha-2,6-sialylation of N-acetyllactosamine sequences in ras-transformed rat fibroblasts correlates with high invasive potential.

Through cloning experiments with the FRras EJ4 cell line, previously described to exhibit a Sambucus nigra agglutinin (SNA)+ phenotype, three clones with a SNA- phenotype were isolated. All the selected SNA+ and SNA- clones expressed the ras oncoprotein and cloned in soft agar with the same efficiency. We were interested in studying the adhesion and invasion properties of the FRras cells presenting a SNA + or - phenotype. They were first compared in their biochemical properties and we found that FRras SNA- were characterized by a low alpha-2,6-sialylation of their cell surface glycoproteins and a low beta-galactoside alpha-2,6 sialytransferase activity. Using in vitro invasion assays, FRras cells exhibiting a low alpha-2,6-sialylation on their surface were found to have a low invasive potential compared to their counterpart SNA+. FRras SNA-clones exhibit a different morphology from that of FRras SNA+ clones. Moreover, homotypic aggregation assays indicated that FRras SNA- were more cohesive with each other and adhesion assays showed that they were more adhesive to fibronectin.

Amino Sugars↗
PubMed1995

[Transcription factors of the PEA3 group in mammary cancer].

Prognosis factors such as mutated or amplified oncogenes are used in the treatment of breast cancer. We have recently shown that the members of the PEA3 group (ER81, ERM and PEA3) from the transcription factor family of the ets genes are overexpressed in breast cancer tumors arising from MMTV-neu transgenic animals. Moreover, we have shown that ER81, and in a lesser extent ERM and PEA3, are not expressed in the estrogen and/or progesterone receptor-positive mammary cancer cell lines, whereas they are expressed in the receptor negative ones. Our research interest in now focused on the role(s) of these oncogenes in the development and the regulation of breast tumors.

Amino Acid Sequence↗
PubMed1994

Stromal expression of c-Ets1 transcription factor correlates with tumor invasion.

The stroma reaction has an important role in tumor growth, invasion, and metastasis. In various invasive human carcinomas, as well as in a mouse model for tumor invasion, transcripts encoding the transcription factor c-Ets1 were detected within stromal fibroblasts, whereas they were absent in epithelial tumor cells. This expression of c-Ets1 was often increased in fibroblasts directly adjacent to neoplastic cells. Endothelial cells of stromal capillaries were also positive for c-Ets1 expression. In contrast, fibroblasts of corresponding noninvasive lesions and of normal tissues were consistently negative. In cultured human fibroblasts stimulated by basic fibroblast growth factor and tumor necrosis factor alpha, the expression of c-Ets1 correlated with the accumulation of transcripts for potential target genes, collagenase-1 and stromelysin-1. The same correlation was observed in some of the invasive carcinomas investigated. These results suggest that c-Ets1 participates in the regulation of tumor invasion in vivo.

Adult↗
PubMed1994

A residue of the ETS domain mutated in the v-ets oncogene is essential for the DNA-binding and transactivating properties of the ETS-1 and ETS-2 proteins.

The c-ets-1 locus encodes two transcription factors, p54c-ets-1 and p68c-ets-1 that recognize purine-rich motifs. The v-ets oncogene of the avian retrovirus E26 differs from its cellular progenitor p68c-ets-1 by two amino acid substitutions (alanine 285 and isoleucine 445 in c-ets-1 both substituted by valine in v-ets, mutations A and B respectively) and its carboxy-terminal end (mutation C). The B mutation affects a well conserved residue in the carboxy-terminal 85 amino acids, ETS DNA-binding domain. To address the biological relevance of the B mutation found between v-ets and c-ets-1, we have randomly mutagenized isoleucine 445 of p68c-ets-1 by polymerase chain reaction. Using in vitro gel mobility shift assays, we show that this residue is crucial for the binding properties of c-ets-1 since the 12 mutations we have generated at this position, all diminish or even abolish the binding, to the 'optimized' Ets-1 binding site (EBS), of 35 kDa proteins corresponding to the 311 carboxy-terminal residues of c-ets-1. Among them, substitutions of isoleucine to glutamic acid, glycine or proline have the highest inhibitory effects. Similar results were obtained when the same mutations were introduced either in full-length p68c-ets-1 protein or into a carboxy-terminal polypeptide of 109 amino acids encompassing the ETS-domain which has previously been shown to display a very high binding activity as compared with the full-length protein. Consistent with the in vitro results, point mutations in p68c-ets-1 that decrease binding activity to EBS abrogate its ability to transactivate reporter plasmids carrying either the TPA Oncogene Response Unit of the Polyoma virus enhancer (TORU) or a sequence derived from the HTLV-1 LTR. Furthermore, as this isoleucine residue is rather well-conserved within the ETS gene family, we show that mutation of the corresponding isoleucine of c-ets-2 into glycine also abrogates its DNA-binding and hence, transactivating properties. Thus, the v-ets B mutation highlights the isoleucine 445 as an essential amino acid of the c-ets-1 and c-ets-2 DNA-binding domains.

3T3 Cells↗
PubMed1994

[How tumors abuse their host: the transcription factor c-ets1 and the regulation of tumor angiogenesis or invasion].

During their progression, epithelial tumors induce a stromal reaction essential for their development and for metastasis. In situ hybridization studies have revealed that the protooncogene c-ets1 is expressed in endothelial cells at the beginning tumor angiogenesis, and in stromal fibroblasts surrounding invasive tumors. C-ets1 encodes a transcription factor that may activate the transcription of genes encoding collagenase 1, stromelysin 1 and urokinase plasminogen activator, proteases involved in extracellular matrix degradation. A working hypothesis is that c-Ets1 takes part in regulating invasive processes by controlling the transcription of these genes. Experimental evidences that may confirm this hypothesis will be discussed.

Animals↗
PubMed1994

Molecular cloning and characterization of human ERM, a new member of the Ets family closely related to mouse PEA3 and ER81 transcription factors.

The ets-related transcription factors PEA3 and ER81 have recently been isolated and characterized in the mouse. They share 95% identity in a 85 amino acid (AA) domain termed the ETS domain which is responsible for DNA binding, and therefore they form an Ets family group. By screening a human testis cDNA library with a probe containing the mouse PEA3 ETS domain, we isolated a 2.2 kb clone containing a 510 AA open reading frame. Since the ETS domain, which is localized in the carboxy terminal region of the encoded protein, is 95% and 96% identical to that of PEA3 and ER81, respectively, we named this new member 'Ets Related Molecule PEA3-like' (ERM). Although the first 120 AA in the amino-terminal region of ERM share 47% identity with PEA3 and 66% with ER81, ERM contains a central region of approximately 35 AA not found in the two mouse proteins. Gel shift analysis indicates that the full-length ERM protein is able to bind specifically to an oligonucleotide containing the consensus nucleotide core sequence GGAA recognized by the Ets proteins. Moreover, in vitro translation of 83 AA of the ERM ETS domain led to the production of a truncated protein which also binds to DNA. Though differential expression is observed in primary tumors and normal lymphocytes do not express ERM, this gene is almost ubiquitously expressed in human normal tissues. ERM mRNA is highly expressed in brain as well as in placenta and, to a lesser degree, in lung, pancreas, and heart. Moreover, almost all human cell lines tested express it at varying levels. In mouse tissues, we showed that PEA3 and ER81 mRNAs display restricted expression, whereas ERM is almost ubiquitously expressed as observed for human tissues. Altogether these results indicate that ERM is clearly a new ets family member and not the human equivalent of PEA3 or ER81.

Amino Acid Sequence↗
PubMed1993

High levels of c-rel expression are associated with programmed cell death in the developing avian embryo and in bone marrow cells in vitro.

To determine the physiological processes in which the transcription factor c-Rel may act, we have examined its pattern of expression in the avian embryo by in situ hybridization. These studies showed that c-rel is expressed ubiquitously at low levels and at high levels in isolated cells undergoing programmed cell death by apoptosis or autophagocytosis. To further establish a functional link between expression of c-rel and cell death, we examined the biological consequences of c-rel overexpression in vitro. In primary avian fibroblasts, overexpression of c-rel leads to transformation and dramatic life span extension. In contrast, bone marrow cells expressing high levels of c-rel undergo a process of programmed cell death displaying features of both apoptosis and autophagocytic cell death. Thus, these experiments suggest a critical role for c-rel not only in the control of cell proliferation, but also in the induction of cell death.

Age Factors↗
PubMed1993

Identification and analysis of the chicken c-mil promoter: possible involvement of Sp1- and Ets-related proteins.

We have determined the exon organization in the 5' region of the chicken c-mil gene and identified its promoter. A 0.44-kb fragment containing the 5' terminus of the c-mil gene showed strong promoter activity when placed upstream of the bacterial chloramphenicol acetyltransferase gene and transfected into chicken embryo fibroblasts (CEF). By primer extension analysis, multiple transcriptional start sites were detected within the promoter region. Nucleotide sequence analysis revealed that the c-mil promoter had a high G + C content (71.8%) and contained multiple GC box-like sequences, but no TATA or CAAT boxes. Deletion analysis of 5' upstream sequences showed that the minimal region required for maximal promoter activity in CEF resides in the 99 bp located immediately upstream of the major initiation site. This region contains two putative Sp1 binding sites and one PU box/PEA3 motif, defined as a recognition element for members of the Ets gene family. These sequences bound proteins present in nuclear extracts of CEF as well as in vitro synthesized Ets-related proteins, suggesting that the binding of Sp1 or related proteins and of Ets-related proteins within the promoter is important for modulation of the mil gene.

Animals↗
PubMed1993

Interconnection between thyroid hormone signalling pathways and parvovirus cytotoxic functions.

Nonstructural (NS) proteins of autonomous parvoviruses can repress expression driven by heterologous promoters, an activity which thus far has not been separated from their cytotoxic effects. It is shown here that, in transient transfection assays, the NS-1 protein of the parvovirus minute virus of mice (MVMp) activates the promoter of the human c-erbA1 gene, encoding the thyroid hormone (T3) receptor alpha. The endogenous c-erbA1 promoter is also a target for induction upon MVMp infection. Moreover, T3 was found to up-modulate the level of cell sensitivity to parvovirus attack. These data suggest an interconnection between T3 signalling and NS cytotoxic pathways.

Animals↗
PubMed1993

Structure and DNA-binding properties of Pax-QNR, a paired box- and homeobox-containing gene.

After differential screening of a complementary DNA library constructed from quail neuroretina cells (QNR) infected with the v-myc-containing avian retrovirus MC29, we have isolated a complementary DNA clone which identifies a mRNA essentially expressed in the neuronal layer of the retina. This complementary DNA encodes a protein containing paired box and homeobox domains. This gene, called Pax-QNR, is homologous to the murine Pax-6 and human AN genes, which are mutated in the autosomal dominant mutation small eye (Sey) of the mouse and aniridia in humans. Here, we report the genomic exon-intron organization, as well as the existence of alternative splicing events taking place at both the 5' end and the middle part of the gene. A Pax-QNR clone translated in reticulocyte lysate directed the synthesis of a 46 kilodalton protein able to bind specifically to the e5 sequence present upstream of the Drosophila even-skipped gene and target of the Drosophila paired protein. The Pax-QNR paired and homeobox domains individually expressed in bacteria are both able to recognize the e5 sequence.

Alternative Splicing↗
PubMed1993

The two functionally distinct amino termini of chicken c-ets-1 products arise from alternative promoter usage.

The chicken c-ets-1 locus gives rise to two distinct transcription factors differing by structurally and functionally unrelated N-termini. p54c-ets-1 shows a striking phylogenetic conservation from Xenopus to humans, while p68c-ets-1, the cellular counterpart of the E26-derived v-ets oncogene, is apparently restricted to avian and reptilian species. In the chick embryo, both mRNAs are expressed in a wide array of tissues of mesodermal origin; however, in the embryo and after hatching, p68c-ets-1 is excluded from lymphoid cells where p54c-ets-1 accumulates. In this report, we define the basis of the differential expression of the chicken c-ets-1 products to assess their different potentials as transcription factors. We demonstrate that the two distinct N-termini arise from alternative promoter usage within the chicken c-ets-1 locus. Examination of both promoters reveals that transcription initiates from multiple sites, consistent with the absence of TATA and CAAT elements. Of these two regulatory regions, only the one that initiates the p54c-ets-1 mRNA synthesis is of the G + C-rich type, and its organization is conserved in humans. The avian-specific p68c-ets-1 promoter activity was enhanced by its own product. In addition, we identify numerous potential binding sites for lymphoid-specific transcription factors that might contribute to a tight repressor effect in lymphoid tissues.

Amino Acid Sequence↗
PubMed1993

p54c-ets-1 and p68c-ets-1, the two transcription factors encoded by the c-ets-1 locus, are differentially expressed during the development of the chick embryo.

The chicken c-ets-1 proto-oncogene encodes two transcription factors, p54c-ets-1 and p68c-ets-1, which contain the same DNA-binding domain but differ in their transactivating activities. We have investigated the spatial and temporal distribution of the transcripts encoding p54c-ets-1 and p68c-ets-1 throughout the development of the chick embryo. We report that p68c-ets-1 as well as p54c-ets-1 is expressed in a wide variety of cells of mesodermal origin, including endothelial cells and mesenchymal cells interacting with epithelium. However, whereas p54c-ets-1 transcripts are detected in most cells, p68c-ets-1 transcripts are restricted to a subset of these cells, randomly distributed. In contrast, p54c-ets-1 is expressed in the absence of p68c-ets-1 in T and B lymphocytes. We show that, during erythropoiesis, both p68c-ets-1 and p54c-ets-1 are expressed in immature erythroid cells in extraembryonic blood islands. The pattern of expression of p54c-ets-1 and p68c-ets-1 during embryonic development suggests the involvement of these transcription factors in the regulation of morphogenetic processes. In addition, we provide the first clue that p68c-ets-1, the cellular progenitor of the v-ets oncogene, is expressed in erythroid cells. This result is very important with respect to the properties of the v-ets oncogene, which confers on the retrovirus E26 the ability to transform erythroid cells.

Alternative Splicing↗
PubMed1992

Evolution of the nuclear receptor gene superfamily.

Nuclear receptor genes represent a large family of genes encoding receptors for various hydrophobic ligands such as steroids, vitamin D, retinoic acid and thyroid hormones. This family also contains genes encoding putative receptors for unknown ligands. Nuclear receptor gene products are composed of several domains important for transcriptional activation, DNA binding (C domain), hormone binding and dimerization (E domain). It is not known whether these genes have evolved through gene duplication from a common ancestor or if their different domains came from different independent sources. To test these possibilities we have constructed and compared the phylogenetic trees derived from two different domains of 30 nuclear receptor genes. The tree built from the DNA binding C domain clearly shows a common progeny of all nuclear receptors, which can be grouped into three subfamilies: (i) thyroid hormone and retinoic acid receptors, (ii) orphan receptors and (iii) steroid hormone receptors. The tree constructed from the central part of the E domain which is implicated in transcriptional regulation and dimerization shows the same distribution in three subfamilies but two groups of receptors are in a different position from that in the C domain tree: (i) the Drosophila knirps family genes have acquired very different E domains during evolution, and (ii) the vitamin D and ecdysone receptors, as well as the FTZ-F1 and the NGF1B genes, seem to have DNA binding and hormone binding domains belonging to different classes. These data suggest a complex evolutionary history for nuclear receptor genes in which gene duplication events and swapping between domains of different origins took place.

Amino Acid Sequence↗