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D Stéhelin

Publications and source records attributed to D Stéhelin.

At least 55 records · Page 3Linked to original sources
PubMed1992

Expression patterns of c-myb and of v-myb induced myeloid-1 (mim-1) gene during the development of the chick embryo.

The v-myb oncogene of the acute avian leukemia virus E26 encodes a transcription factor that directly regulates the promyelocyte-specific mim-1 gene (Ness, S.A., Marknell, A. and Graf, T. Cell, 59, 1115-1125). We have investigated the relationship between the c-myb proto-oncogene and the transcription of the mim-1 gene both in vitro and in vivo. We demonstrate that the c-myb protein can transactivate the transcription of mim-1 in a transient transfection assay. In the chick embryo, we confirm that mim-1 is specifically expressed during granulopoiesis and we show that the expression of c-myb and mim-1 are perfectly correlated in the granulocytic spleen and pancreas. However we suggest that mim-1 is efficiently transcribed in the absence of c-myb in the yolk sac and in the promyelocytes at the onset of the colonization of the bursa of Fabricius. On the other hand c-myb transcripts detected in the early hemopoietic progenitor cells, in lymphoid cells and in proliferative epithelia are never associated with mim-1 transcription. We conclude that the granulocyte-specific mim-1 gene is regulated by c-myb-dependent and c-myb-independent mechanisms depending upon the environment in which granulocytic precursor cells differentiate.

Animals↗
PubMed1991

The relationship between cell proliferation and the transcription of the nuclear oncogenes c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo.

We have described the expression of three nuclear protooncogenes, c-myc, c-myb and c-ets-1 during feather morphogenesis in the chick embryo. In parallel with the expression patterns obtained by in situ hybridization, we have mapped the spatial distribution of S-phase cells by monitoring the incorporation of 5-bromodeoxyuridine. We do not detect c-myc or c-myb transcripts during the early stages when S-phase cells are scattered in the dermis and in the epidermis. Rather c-ets-1 transcripts are abundant in the dermal cells which divide and accumulate under the uniform epidermis. At the onset of the formation of the feather bud, cells within each rudiment cease DNA replicative activities and c-myc transcripts are detected both in the epidermis and in the underlying dermis. This expression precedes the reentry into the S phase. The transcription of c-myb, which has been previously tightly linked to hemopoietic cells is also detected in the developing skin. This expression is essentially located in proliferating epidermal cells on and after the beginning of feather outgrowth. As feather outgrowth proceeds, the distribution of c-myc and c-myb transcripts is restricted to the highly proliferating epidermis. In contrast c-ets-1 transcripts are never detected in the epidermis. During the later stages of skin morphogenesis, the transcription of c-ets-1 is restricted to the endothelial cells of blood vessels, as previously described. We suggest that the differential expression of these nuclear oncogenes reflects the activation of different mitotic controlling pathways during the development of the skin.

Animals↗
PubMed1991

Cloning, sequencing, and expression of two Xenopus laevis c-ets-2 protooncogenes.

In a general approach to identify genes important in the control of genetic expression during development of Xenopus laevis, two complementary DNAs corresponding to two different c-ets-2 genes were cloned and sequenced. One of these complementary DNAs appears to be almost full length. The two variant genes differ in their overlapping sequences by 87 nucleotide substitutions, leading to 17 amino acid modifications in the proteins, 8 of them being conservative. All but one of these changes map outside of the 142 COOH-terminal residues, a region critical for nuclear localization and DNA binding in the ets proteins. Features potentially important for the biological activity of the gene products are conserved. Two transcripts (3.2 and 1.7 kilobases) with maternal characteristics are detected at a constant level from stages II/III of oogenesis to stage 10 of embryogenesis. They later decline to hardly detectable levels at stages 30-40. Variable amounts of the same transcripts are observed in many adult tissues. All of these characteristics support the idea that the ets-2 gene products play an important role during embryogenesis, as well as in adult life. Indeed, they act as ubiquitous transcriptional activators, as recently demonstrated by several investigators (C. V. Gunther, J. A. Nye, R. S. Bryner, and B. J. Graves, Genes & Dev., 4: 667-679, 1990; R. Bosselut, J.F. Duvall, A. Gegonne, M. Bailly, A. Hemar, J. Brady, and J. Ghysdael, EMBO J., 9: 3137-3144, 1990; R. Wasylyk, C. Wasylyk, P. Florès, A. Bègue, D. Leprince, and D. Stéhelin, Nature (Lond.), 346: 191-193, 1990).

Amino Acid Sequence↗
PubMed1990

[Amplification of mitochondrial DNA fragments from ancient human teeth and bones].

We extracted and visualized DNA from ancient human teeth and bones of 150 to 5,500 years B.P. from three deposits from the south of France. The DNA extracted was used as template for PCR with specific primers corresponding to a portion of the human mitochondrial genome. In our samples, we have amplified a specific DNA fragment of 121 bp which, in the case of one bone of 150 years B.P. has been cloned and sequenced. We show that this sequence is identical to the homologous region of human mitochondrial DNA. The striking implications of this new method for archaeological and paleontological studies are exposed.

Base Sequence↗
PubMed1989

Two nuclear oncogenic proteins, P135gag-myb-ets and p61/63myc, cooperate to induce transformation of chicken neuroretina cells.

Several studies have shown that full transformation of primary rodent fibroblasts can be achieved in vitro through the cooperation of two oncogenes (usually one nuclear and one cytoplasmic) classified on the basis of different complementation groups. We have shown previously that cooperation between v-mil (cytoplasmic, serine-threonine kinase product), and v-myc (nuclear, DNA-binding product) is required to transform 7-day-old chicken neuroretina cells, which in usual culture medium do not rapidly proliferate. v-mil induces sustained growth of chicken neuroretina cells without transformation; v-myc fails to stimulate the proliferation of chicken neuroretina cells but is required to achieve transformation of the proliferating cells. Here, we present results indicating that the P135gag-myb-ets nuclear protein of avian erythroblastosis virus E26 is able to induce proliferation but not transformation of chicken neuroretina cells. v-myc is required in addition to P135gag-myb-ets to achieve chicken neuroretina cell transformation. In contrast, we found that the P135gag-myb-ets and P100gag-mil proteins are not able to cooperate in this system.

Animals↗
PubMed1988

Expression of ETS proto-oncogenes in astrocytes in human cortex.

In order to investigate a possible function of ETS proto-oncogenes in human brain, we incubated a polyclonal antibody raised against the viral region of E26 homologous to ETS1 and ETS2 with human brain frontal cortex sections. Our results show that this antibody decorates astrocytes but not neurons. By using astrocytomas of different grades as a source of astrocytes, we demonstrate the presence of ETS1 and ETS2 messenger RNAs and proteins. This leads to the idea that ETS genes are expressed in cells with dividing potentialities in human cortex and that they could provide a new marker for glial cells. Recently, a microduplication on chromosome 21 including ETS2 locus was described in karyotypically 'normal' Down's syndrome and suspected in Alzheimer's disease; when testing Alzheimer's disease-affected brain cortex sections, no obvious difference was observed with the technique used.

Antigens, Viral↗
PubMed1988

Identification in chickens of an evolutionarily conserved cellular ets-2 gene (c-ets-2) encoding nuclear proteins related to the products of the c-ets proto-oncogene.

In chicken cells, we previously identified a set of proteins (p58-64) structurally related to, but distinct from, the products encoded by the c-ets proto-oncogene. We report here the isolation and nucleotide sequence of a cDNA encoding nuclear products of mol. wt 58, 60, 62 and 64 kd, indistinguishable from those detected in chicken cells. The p60 and p64 species appear to represent phosphorylated versions on serine and threonine residues of p58 and p62. The homology of p58-64 to other ets-related proteins, including the v-ets encoded domain of the transforming protein of avian leukemia virus E26 and p54c-ets, the translation product of the chicken (Ck) c-ets gene, is confined to two regions of 175 and 96 amino acid residues localized respectively at the carboxy-terminal domain and close to the amino-terminal domain of these molecules. This cDNA corresponds to a gene localized in a locus distinct from that of c-ets which is transcribed as a 4.0-kb RNA species in most chicken tissues. We also identified the human (Hu) c-ets-2-encoded products as two proteins of 60 and 62 kd, highly related to chicken p58-64. This, together with the fact that the amino acid sequence of the cDNA encoding p58-64 is 95% identical to the reported partial sequence of a Hu-c-ets-2 cDNA, indicates that p58-64 are the translation products of the Ck-c-ets-2 gene.

Amino Acid Sequence↗
PubMed1988

Mitogenic stimulation of thymocytes results in the calcium-dependent phosphorylation of c-ets-1 proteins.

Human, murine and chicken c-ets-1 proteins migrate in SDS-polyacrylamide gels as multiple species. We show here that most if not all of this heterogeneity is due to phosphorylation events occurring predominantly on serine and to a lesser extent on threonine residues. These phosphorylations can be specifically and rapidly stimulated by treatment with the calcium ionophore A23187 or abolished by lowering the extracellular calcium concentration to less than 0.1 microM. The products encoded by c-ets-2 are also phosphorylated in a Ca2+-dependent manner, indicating that these modifications have been conserved in the products encoded by different members of the same gene family. In thymocytes, where the expression of c-ets-1 is elevated as compared with other cell types, c-ets-1 protein phosphorylation occurs after stimulation with mitogenic doses of concanavalin A, is short lived and is strictly dependent upon extracellular Ca2+ sources. This suggests that the c-ets-1 gene product may play a role in the Ca2+-mediated early events linked to T-cell activation.

Animals↗
PubMed1987

Heart tumors specifically induced in young avian embryos by the v-myc oncogene.

To determine if expression of the v-myc oncogene had any effect during ontogeny, we injected avian myelocytomatosis virus strain MC29 into avian embryos at various stages of development. The injection of MC29 at embryonic day 2 (E2) or 3 (E3) caused, about 10 days later, rhabdomyosarcomas of the heart and, in some cases, skin muscle hypertrophy. When the injection was performed at E4 or E5, the number of heart tumors declined, whereas the number of skin muscle tumors increased significantly. The p110gag-myc protein was found in all tumors analyzed. When the virus was injected intravenously into E10 embryos, no tumors appeared during embryonic life, in striking contrast to the results obtained from injections at earlier stages. The monoclonal antibody 13F4, which is specific for the myogenic lineage, bound strongly to tumoral heart tissue, whereas it bound weakly to normal cardiac cells. Comparison of the peaks of tumor incidence in relationship to the timing of injection suggests that the v-myc product could interfere in vivo with an early step of the muscle lineage differentiation program. In addition, we show that the p58c-myc protein, which is supposed to play an important role in the control of cell proliferation, is only faintly detected in the heart of normal E3 embryos, in contrast to limb and tail buds, which readily express detectable levels of p58c-myc.

Adrenal Gland Neoplasms↗
PubMed1987

The human c-myc exon 1 product: preparation of antisera and analysis of its expression.

We investigated the coding capacity of the previously reported open reading frame (ORF) of the human c-myc exon 1. By in vitro translation assay, we found that exon 1 ORF was translated into a 20-kd protein (p20 protein). In order to obtain antisera raised against the p20 protein, we constructed a plasmid vector which expressed most of the exon 1 ORF as a 25-kd (P25) protein in Escherichia coli. Polyclonal antisera raised against this P25 protein specifically precipitated a chimeric protein which contained exon 1-related amino acid sequences. We used these antisera to test for the existence of an exon 1 product in human cells. In the human cell lines tested, these antisera have failed so far to detect any exon 1-related proteins. However, exon 1-related proteins were detected with the anti-p20 antisera in quail embryonic cells (QEC) transfected by human c-myc recombinants constructed to express such proteins, but were expressed at low levels compared with the human c-myc protein also expressed in the transfected QEC. Our results suggest that secondary structure of the mRNA could be responsible for the low expression of the exon 1 product in QEC.

Animals↗
PubMed1986

[Preparation and characterization of specific antisera directed against different polypeptide domains encoded by the c-myc oncogene for studying the expression of this gene introduced into quail or rat cells].

By using bacterial expression vectors, we have prepared antisera directed against two polypeptidic domains encoded by exons 2 and 3 of the human c-myc oncogene. These antisera which detect specifically the human c-myc proteins allow us to analyse the expression of human c-myc gene activated by retroviral sequences and introduced in quail embryo cells (QEC) or in established rat embryo fibroblastic cell line (208 F). Although human myc mRNA are expressed in the two cell types, the p64/p67 human c-myc proteins are only detected in the QEC.

Animals↗
PubMed1983

Virus gene expression in rat cells transformed by avian myelocytomatosis virus strain MC29 and avian erythroblastosis virus.

Virus gene expression in rat cells transformed by either avian myelocytomatosis virus strain MC29 or avian erythroblastosis virus has been studied by biological and biochemical methods. In the clones examined, virus-specific sequences were found to be transcribed into RNA and, in most clones, the characteristic gag-related proteins could be identified. The transformed rat cells were fused to permissive chick cells and the rescued virus was shown to transform both chick embryo fibroblasts and the appropriate haemopoietic cell type in chick bone marrow cultures. These results clearly demonstrate that, as with the non-defective avian sarcoma viruses, the genetic information responsible for transformation by the defective avian leukaemia viruses can be expressed in non-permissive mammalian host cells as well as in permissive avian cells.

Alpharetrovirus↗
PubMed1981

Revertants of rats cells transformed by avian erythroblastosis virus.

Morphological revertants of the avian erythroblastosis virus (AEV)-transformed rat cell line ATla were isolated and characterised. The revertants are similar to the uninfected parental rat cell line in that they have regained an organized cytoskeleton and they are no longer capable of anchorage-independent growth. The pattern of integrated viral DNA in the revertants is indistinguishable from that of the transformed parent. However, the revertants do not express the integrated viral genome at either the mRNA or protein level. Phenotypic reversion thus is probably .due to reduced transcription of the AEV-transforming gene below a threshold necessary to induce morphological transformation.

Alpharetrovirus↗