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A Gegonne

Publications and source records attributed to A Gegonne.

At least 19 recordsLinked to original sources
PubMed2001

TAFII55 binding to TAFII250 inhibits its acetyltransferase activity.

The general transcription factor, TFIID, consists of the TATA-binding protein (TBP) associated with a series of TBP-associated factors (TAFs) that together participate in the assembly of the transcription preinitiation complex. One of the TAFs, TAF(II)250, has acetyltransferase (AT) activity that is necessary for transcription of MHC class I genes: inhibition of the AT activity represses transcription. To identify potential cellular factors that might regulate the AT activity of TAF(II)250, a yeast two-hybrid library was screened with a TAF(II)250 segment (amino acids 848-1279) that spanned part of its AT domain and it's the domain that binds to the protein, RAP74. The TFIID component, TAF(II)55, was isolated and found to interact predominantly with the RAP74-binding domain. TAF(II)55 binding to TAF(II)250 inhibits its AT activity. Importantly, the addition of recombinant TAF(II)55 to in vitro transcription assays inhibits TAF(II)250-dependent MHC class I transcription. Thus, TAF(II)55 is capable of regulating TAF(II)250 function by modulating its AT activity.

Acetylation↗
PubMed2000

Determinants of vitellogenin B1 promoter architecture. HNF3 and estrogen responsive transcription within chromatin.

The liver-specific vitellogenin B1 promoter is efficiently activated by estrogen within a nucleosomal environment after microinjection into Xenopus laevis oocytes, consistent with the hypothesis that significant nucleosome remodeling over this promoter is not a prerequisite for the activation by the estrogen receptor (ERalpha). This observation lead us to investigate determinants other than ERalpha of chromatin structure and transcriptional activation of the vitellogenin B1 promoter in this system and in vitro. We find that the liver-enriched transcription factor HNF3 has an important organizational role for chromatin structure as demonstrated by DNase I-hypersensitive site mapping. Both HNF3 and the estrogen receptor activate transcription synergistically and are able to interact with chromatin reconstituted in vitro with three positioned nucleosomes. We propose that HNF3 is the cellular determinant which establishes a promoter environment favorable to a rapid transcriptional activation by the estrogen receptor.

Animals↗
PubMed1999

Mi-2 complex couples DNA methylation to chromatin remodelling and histone deacetylation.

Methylation of DNA at the dinucleotide CpG is essential for mammalian development and is correlated with stable transcriptional silencing. This transcriptional silencing has recently been linked at a molecular level to histone deacetylation through the demonstration of a physical association between histone deacetylases and the methyl CpG-binding protein MeCP2 (refs 4,5). We previously purified a histone deacetylase complex from Xenopus laevis egg extracts that consists of six subunits, including an Rpd3-like deacetylase, the RbA p48/p46 histone-binding protein and the nucleosome-stimulated ATPase Mi-2 (ref. 6). Similar species were subsequently isolated from human cell lines, implying functional conservation across evolution. This complex represents the most abundant form of deacetylase in amphibian eggs and cultured mammalian cells. Here we identify the remaining three subunits of this enzyme complex. One of them binds specifically to methylated DNA in vitro and molecular cloning reveals a similarity to a known methyl CpG-binding protein. Our data substantiate the mechanistic link between DNA methylation, histone deacetylation and transcriptional silencing.

Adenosine Triphosphatases↗
PubMed1997

Cellular and viral trans-acting factors modulate N-myc2 promoter activity in woodchuck liver tumors.

Activation of the N-myc2 oncogene by integration of woodchuck hepatitis virus (WHV) DNA is a central event in woodchuck liver oncogenesis. In this study, we have evaluated the influence of several cellular and viral trans-acting factors and mediators of inflammation on N-myc2 promoter activity in hepatoma cell lines. Ets oncoproteins, including Ets1, Ets2 and PEA3 efficiently activated a chimeric N-myc2 promoter/luciferase reporter gene. By electrophoretic mobility shift assays, we show that Etsl and Ets2 proteins can efficiently bind two consensus Ets sites located within a 59 bp sequence upstream of the N-myc2 transcription start site. Site-directed mutagenesis of these Ets-binding motifs abolished transactivation of the N-myc2 promoter by Ets proteins. Addition of interleukin-6 (IL-6) induced a weak but reproducible activation of the N-myc2 promoter, while IL-1 was ineffective. We further show that the N-myc2 promoter can be transactivated by the hepadna-virus X protein, and that distal promoter sequences are required for both IL-6 and X responsiveness. Similar effects of these factors were observed in the context of the N-myc2 promoter activated by WHV cis-regulatory elements. In view of the high-level expression of the N-myc2 oncogene in most woodchuck liver tumors, the Ets oncoproteins, inflammation-associated cytokine IL-6 and the viral X transactivator might play important roles in hepadnavirus-associated tumorigenesis.

Animals↗
PubMed1993

Characterization of a hepatoma mRNA transcribed from a third promoter of a 6-phosphofructo-2-kinase/fructose-2,6-bisphosphatase-encoding gene and controlled by ets oncogene-related products.

6-Phosphofructo-2-kinase (EC 2.7.1.105)/fructose-2,6-bis-phosphatase (EC 3.1.3.46) catalyzes the synthesis and degradation of fructose 2,6-bisphosphate, a ubiquitous stimulator of glycolysis. The liver (L-type) and muscle (M-type) mRNAs for this bifunctional enzyme arise from distinct promoters of the same gene. We have now characterized in rat hepatoma FTO2B cells another mRNA, which is transcribed from a third promoter of that gene. This F-type mRNA is present in fetal rat liver and muscle, in rat placenta, and in several established rat cell lines. The F promoter contains no TATA box but contains several binding sites for Sp1 and for members of the ets oncogene family. Transfection of FTO2B cells with constructs containing the intact or mutagenized F promoter showed that its activity depends mainly on one of these sites. This site bound a heteromeric FTO2B cell protein indistinguishable from the ets-related GA binding protein alpha/ankyrin-repeats GA binding protein beta transcription factor.

Animals↗
PubMed1992

A phorbol ester response element within the human T-cell receptor beta-chain enhancer.

The activity of the T-cell receptor beta-chain gene enhancer is increased by activators of the protein kinase C pathway during T-cell activation. Analysis of mutant enhancer constructs identified two elements, beta E2 and beta E3, conferring phorbol ester inducibility. Multimerized beta E2 acted in isolation as a phorbol ester-responsive element. Both beta E2 and beta E3, which contain a consensus Ets-binding site, were shown to bind directly to the product of the c-ets-1 protooncogene. Both regions also bound a second factor, core-binding factor. Mutation of the beta E2 Ets site abolished the inducibility of the beta E2 multimer. beta E2 and beta E3 Ets site mutations also profoundly affected activity and inducibility of the enhancer. In contrast, enhancer activity but not its inducibility was affected by mutation of the beta E2 core-binding factor site. Cotransfection studies showed that Ets-1 specifically repressed activity of the multimerized beta E2 element and the complete T-cell receptor beta-chain enhancer. These data show that the T-cell receptor beta-chain enhancer responds to protein kinase C-mediated activation signals via a functional domain, composed of two elements, which contains binding sites for Ets transcription factors and which is negatively regulated by Ets-1.

Base Sequence↗
PubMed1992

Analysis of the DNA binding and transcriptional activation properties of the Ets1 oncoprotein.

The c-ets1 gene product (Ets1) is the prototype of a family of sequence-specific transcriptional activators which have been implicated in various developmental processes and in the response of cells to a variety of extracellular stimuli. We report here a structure-function analysis of the DNA binding and transcriptional activation properties of Ets1. The minimal region required for specific DNA binding is located at the carboxy-terminus of Ets1, a domain highly conserved in all known members of the Ets family. Transcriptional activation by Ets1 in mammalian cells requires an additional domain of 110 amino acids characterized by a high content of acidic residues and localized in the amino-terminal half of the protein. This domain also functions as a transcriptional activation domain in yeast cells when linked to the heterologous DNA binding domain of Gal4. In contrast to its conservation in Ets1 proteins across vertebrate species, this activation domain is not conserved in other members of the Ets family. These results indicate that an important level of specificity between different members of the Ets family may reside in the differential interactions of their respective activation domains with distinct general transcription factors or different associated coactivators.

Base Sequence↗
PubMed1987

The bovine leukemia virus p34 is a transactivator protein.

Recombinant Moloney murine retroviruses containing the BLV post-envelope long open reading frame were constructed and transfected into the psi 2 packaging cell line. They were shown to encode and to express a 34-kd protein able to transactivate the BLV long terminal repeat-directed gene expression in the respective transfected cells. These data demonstrate that the BLV X-LOR gene encodes a p34 transactivator product. Furthermore, the different cell lines produced infectious recombinant retroviruses capable of transferring X-LOR genes into recipient cells. The availability of the BLV transactivator protein should allow us to understand the role of the transactivator protein in BLV-induced leukemogenesis.

Animals↗
PubMed1987

Maternal origin of a de novo balanced t(21q21q) identified by ets-2 polymorphism.

Molecular investigations were done in a woman with a de novo balanced t(21q21q) discovered because of the birth of a trisomic 21 baby. Polymorphisms detected with probe ets-2 after Msp I digestion showed that both chromosomes 21 involved in the rearrangement were of maternal origin. The most likely hypothesis is that of a disomic 21 oocyte fertilized by a nullisomic 21 sperm.

Chromosomes, Human, Pair 21↗
PubMed1987

Submicroscopic duplication of chromosome 21 and trisomy 21 phenotype (Down syndrome).

A patient with the phenotype of trisomy 21 (Down syndrome) was found to have a normal karyotype in blood lymphocytes and fibroblasts. Assessment of the chromosome 21 markers SOD1, CBS, ETS2, D21S11, and BCEI showed partial trisomy by duplication of a chromosome segment carrying the SOD1, CBS, and ETS2 loci and flanked by the BCEI and D21S11 loci, which are not duplicated. This submicroscopic duplication at the interface of 21q21 and 21q22.1 reduces to about 2000-3000 kb the critical segment the trisomy of which is responsible for the phenotype of trisomy 21.

Adult↗
PubMed1987

The 5' extremity of the v-ets oncogene of avian leukemia virus E26 encodes amino acid sequences not derived from the major c-ets-encoded cellular proteins.

Antibodies were prepared against bacterially expressed polypeptides corresponding to various portions of the v-ets-encoded domain of P135gag-myb-ets, the transforming protein of avian leukemia virus E26. Immunoprecipitation analyses show that ca. 80 v-ets-encoded amino-acids located immediately after the v-myb/v-ets junction are not found in P54/56c-ets, the translation product of the c-ets proto-oncogene, nor in a set of cellular proteins of 64, 62, and 60 kDa related to but distinct from P54/56c-ets. In addition, Northern blot analyses show that these 5' v-ets sequences neither derive from the nontranslated region of the known cellular transcripts hybridizing to a v-ets probe nor from the c-myb transcript or the helper virus genetic information. Tryptic peptide analyses furthermore indicate that, except for these sequences and the last 16 carboxy terminal amino acids of P135gag-myb-ets, the amino acids encoded by v-ets are essentially colinear with those of P54c-ets.

Amino Acid Sequence↗
PubMed1987

Multiple domains for the chicken cellular sequences homologous to the v-ets oncogene of the E26 retrovirus.

We have investigated the structure of chicken genomic DNA homologous to v-ets, the second cell-derived oncogene of avian retrovirus E26. We isolated a c-ets locus spanning ca. 30.0 kilobase pairs (kbp) in the chicken genome with homologies to 1,202 nucleotides (nt) of v-ets (total length, 1,508 nt) distributed in six clusters along 18.0 kbp of the cloned DNA. The 5'-distal part of v-ets (224 nt) was homologous to chicken cellular sequences contained upstream within a single 16.0-kbp EcoRI fragment as two typical exons but not found transcribed into the major 7.5-kb c-ets (or 4.0-kb c-myb) RNA species. Between these two v-ets-related cellular sequences we found ca 40.0 kbp of v-ets-unrelated DNA. Finally, the most 3' region of homology to v-ets in the cloned DNA was shown to consist of a truncated exon lacking the nucleotides coding for the 16 carboxy-terminal amino acids of the viral protein but colinear to one of the two human c-ets loci, c-ets-2.

Animals↗
PubMed1986

Identification in chicken macrophages of a set of proteins related to, but distinct from, the chicken cellular c-ets-encoded protein p54c-ets.

Using an antiserum to a bacterially expressed polypeptide corresponding to 56 amino acids of v-ets, we previously identified in chicken tissues a protein of 54 kd (p54c-ets) which shares extensive sequence homology to the v-ets-encoded domain of the E26-transforming protein p135gag-myb-ets and is thus apparently encoded by the c-ets proto-oncogene. We report here that the anti-ets serum specifically identifies in chicken cells a second set of proteins of 60 kd (p60), 62 kd (p62) and 64 kd (p64) which appear to be highly related to each other but display only a limited domain of homology with p54c-ets and p135gag-myb-ets and are thus probably encoded by a gene(s) partially related to, but different from c-ets. In contrast to p54c-ets which is expressed at high levels in chicken lymphoid tissues, prominent syntheses of p62 and p64 were found in both normal and transformed chicken macrophages but not in avian cells corresponding to immature stages of the myeloid differentiation pathway. These observations together with the fact that differentiation of avian myeloblastosis virus-transformed myeloblasts into macrophage-like cells after treatment with 12-O-tetradecanoylphorbol-13-acetate is accompanied by the synthesis of p62 and p64 suggest a role for these proteins in chicken macrophage differentiation or function. Induction of differentiation of human leukemia cell lines HL60 and U937 into macrophages is also accompanied by the increased synthesis of c-ets-encoded 68 kd, 62 kd and 58 kd proteins.

Animals↗
PubMed1986

Comparison of constitutional and tumor-associated 11;22 translocations: nonidentical breakpoints on chromosomes 11 and 22.

Recurring, site-specific chromosomal rearrangements are associated with several human syndromes and malignant disorders. Such nonrandom translocations involving chromosome 22 in band q11 are numerous and found to be associated with a diversity of neoplasms as well as constitutional disorders. Chromosome 11 in bands q23-q24 is similarly involved in several types of tumors as well as in a recurring constitutional reciprocal translocation with chromosome 22. Here we report the use of chromosomal in situ hybridization to compare the translocation breakpoints in the cytologically indistinguishable constitutional t(11;22) and the tumor-related t(11;22) associated with Ewing sarcoma and peripheral neuroepithelioma. We have shown that the breakpoints can be distinguished from each other with respect to the locus encoding the constant region of the Ig lambda light chain (C lambda) at 22q11 and the ETS1 locus at 11q23----q24; ETS1 has been called hu-ets-1 or human c-ets-1. The tumor-associated chromosome 11 breakpoint is also different from those of leukemias with t(9;11) and t(4;11) translocations. Southern-blot analysis showed no rearrangement of ETS1 in these disorders in the region detected by our probe. ETS1 has also been mapped more precisely to 11q23.3----q24 by in situ hybridization to cells from an individual with an 11q23.3----qter deletion.

Cell Line↗
PubMed1986

Identification and preferential expression in thymic and bursal lymphocytes of a c-ets oncogene-encoded Mr 54,000 cytoplasmic protein.

The avian retrovirus E26 is unique among acute leukemia viruses in its ability to induce transformation of cells belonging to either the myeloid or erythroid lineage. The genome of E26 carries two oncogenes, v-myb and v-ets, that are derived from distinct cellular loci, c-myb and c-ets. We have constructed a plasmid vector that allows expression of part of the coding region of v-ets in a bacterial host. Antisera to the bacterially synthesized ets protein specifically precipitated the E26-encoded P135gag-myb-ets transforming protein. These antisera permitted us to identify a chicken c-ets-encoded protein of Mr 54,000 (P54c-ets) that shares 7 out of 10 of its major [35S]methionine-containing tryptic peptides with the v-ets-encoded domain of P135gag-myb-ets. Unlike P135gag-myb-ets and the Mr 75,000 translation product of c-myb (P75c-myb), which are nuclear proteins, P54c-ets was found to be predominantly cytoplasmic. P54c-ets is expressed at low levels in most cell lines and tissues tested, including bone marrow cells and circulating lymphocytes. P54c-ets, together with a minor but closely related Mr 56,000 protein, was found to be expressed at high levels in chicken thymocytes and bursal lymphocytes.

Animals↗
PubMed1986

[Preparation and characterization of antisera specific to various polypeptide domains corresponding to the v-ets oncogene of the avian leukemia virus E26].

We prepared antisera to three distinct portions of the v-ets oncogene of the avian leukemia virus E26. An antiserum directed against the middle v-ets-encoded domain identifies in different chicken cell lines and normal tissues a c-ets-encoded protein of Mr 54,000 (P54c-ets) and three proteins of Mr 60,000 62,000 and 64,000 partially related to P54c-ets. Antisera directed against the aminoterminal v-ets-encoded domain failed to precipitate P54c-ets or P60/P64. Thus, the E26 specific v-ets oncogene displays a complex structure that includes several distinct portions, the genetic origin of which could be different.

Animals↗