Biomedical subjects

C Wasylyk

Publications and source records attributed to C Wasylyk.

At least 19 recordsLinked to original sources

PubMed1992

A novel modulator domain of Ets transcription factors.

The ets gene family is composed of several oncogenes and codes for transcription factors. The Ets proteins have a similar sequence called the ets domain and bind to the core motif A/CGGAA. We show here that several members of the ets family have different trans-activating properties. The ets domain of Ets-1 is required for DNA binding. Adjacent to this domain there is a novel element that inhibits DNA binding. It appears to alter the structure of the DNA-binding domain before it interacts with DNA. There is a similar sequence in Ets-2 that also inhibits DNA binding. This sequence is absent in alternative splice products of h-Ets-1. PU1, the most distantly related member of the ets gene family, lacks this novel element. It has a distinct DNA-binding specificity that is determined by DNA sequences outside the core motif. These results have important implications for both the oncogenic and normal functions of ets family members.

Amino Acid Sequence↗

PubMed1992

Oncogenic conversion alters the transcriptional properties of ets.

The vEts oncoprotein and its progenitor cEts1(p68) belong to a growing family of transcription factors that are related by the conserved ets domain. We show here that the ets domain and adjacent COOH-terminal amino acids are required for DNA binding by cEts1(p68). vEts differs from cEts1(p68) in both the COOH-terminal sequence and an amino acid substitution in the ets domain. The change in the COOH-terminal sequence markedly decreases its affinity for specific DNA, and the ets domain mutation further diminishes binding. vEts does not trans-activate through the ets (PEA3) motif in vivo. Surprisingly, vEts still efficiently trans-activates the promoters of two genes, stromelysin and collagenase, that are found to be overexpressed in transformed cells. The AP1 motifs of both promoters are required for efficient activation. vEts does not bind to the AP1 motif, even in the presence of cJun and cFos. The DNA-binding domain of Ets1 is required for activation through the AP1 element. Activation is inhibited by the expression of the glucocorticoid and retinoic acid receptors, suggesting that activation by Ets does not involve reversal of negative regulators of AP1. We suggest that activation is by an indirect mechanism involving activation of endogenous genes. Our results show that vEts differs from its progenitor cEts1(p68) in its trans-activating properties. The findings suggest that activation of the Jun and Fos oncoprotein pathway is important for transformation by Ets.

Amino Acid Sequence↗

PubMed1991

The c-Ets oncoprotein activates the stromelysin promoter through the same elements as several non-nuclear oncoproteins.

The c-ets protooncogenes have recently been shown to code for transcription factors that activate the oncogene responsive unit of the polyoma virus enhancer. We show that transcription of the stromelysin gene, which is highly expressed in transformed cells and tumours, is efficiently activated by c-Ets-1 and -2 through two DNA elements. The distal element is a highly conserved palindrome composed of two strong binding sites for c-Ets-1. The proximal element does not bind c-Ets-1, but may be activated indirectly by increased synthesis of c-Jun and c-Fos. Both ets responsive elements mediate activation by the oncoproteins Ha-Ras, v-Src and v-Mos. These results suggest that c-Ets participates in the mechanisms by which stromelysin gene expression is deregulated in transformed cells and tumours.

Animals↗

PubMed1991

Cell-specific regulation of oncogene-responsive sequences of the c-fos promoter.

We have identified oncogene-responsive sequences in the human c-fos promoter that mediate induction of transcription by several nonnuclear oncoproteins and the tumor promoter TPA. These sequences are regulated in a cell-specific manner. (i) In NIH 3T3 cells, the CArG box of the c-fos promoter is sufficient to mediate activation by oncogenes. (ii) In contrast, in HeLa cells, additional flanking sequences are also required, including the outer arm of the serum response element and the FAP site. We also show that the serum response factor, which binds to the CArG box, activates transcription in vivo in NIH 3T3 cells but not in HeLa cells. Finally, we present evidence that the intracellular level of the c-Fos protein could be a major determinant of cell-specific regulation of these oncogene-responsive elements of the c-fos promoter.

Base Sequence↗

PubMed1990

The c-ets proto-oncogenes encode transcription factors that cooperate with c-Fos and c-Jun for transcriptional activation.

Cell transformation by oncogenes leads to changes in gene expression. A key event in this process seems to be activation of the transcription factors AP-1 and PEA 3. Their synergistic activities are required for efficient activation of transcription from different promoters by many different oncogenes, serum growth factors and the tumour promoter TPA. We show here that the products of the ets-1 and -2 proto-oncogenes, whose biological function was previously unknown, are transcription factors that activate transcription through the PEA 3 motif. The p68c-ets-1 protein specifically binds to DNA and contains a transcriptional activation domain. The ets-like gene family therefore seems to encode a new family of transcription factors, apparently unrelated to other transcription factors. The p68c-ets-1 protein cooperates with c-Fos and c-Jun (components of AP-1) for activation of transcription from the oncogene-responsive domain of the polyoma enhancer, indicating that combined activity of all three oncoproteins could be involved in the response of cells to growth stimuli.

Base Sequence↗

PubMed1990

Oncogene v-jun modulates DNA replication.

Cell transformation leads to alterations in both transcription and DNA replication. Activation of transcription by the expression of a number of transforming oncogenes is mediated by the transcription factor AP1 (Herrlich & Ponta, 1989; Imler & Wasylyk, 1989). AP1 is a composite transcription factor, consisting of members of the jun and fos gene-families. c-jun and c-fos are progenitors of oncogenes, suggestion that an important transcriptional event in cell transformation is altered activity of AP1, which may arise either indirectly by oncogene expression or directly by structural modification of AP1. We report here that the v-jun oncogene and its progenitor c-jun, as fusion proteins with the lex-A-repressor DNA binding domain, can activate DNA replication from the Polyoma virus (Py) origin of replication, linked to the lex-A operator. The transcription-activation region of v-jun is required for activation of replication. When excess v-jun is expressed in the cell, replication is inhibited or 'squelched'. These results suggest that one consequence of deregulated jun activity could be altered DNA replication and that there are similarities in the way v-jun activates replication and transcription.

Base Sequence↗

PubMed1989

PEA3 is a nuclear target for transcription activation by non-nuclear oncogenes.

We have found that the activity of the transcription factor PEA3 is regulated by the expression of non-nuclear oncogenes. This factor, although distinct from PEA1 (AP1), is activated by the same oncogenes (v-src, polyoma (Py) middle T, c-Ha-ras, v-mos, v-raf), by tetradecanoyl phorbol-acetate (TPA) and by serum components. We present evidence that PEA3 and PEA1 co-operate in the response of the polyoma virus (Py) alpha domain to oncogene expression. However, in contrast to PEA1, c-fos does not appear to be necessary for activation of PEA3, suggesting that PEA3 is a fos independent target for regulation of transcription by non-nuclear oncogenes.

Animals↗

PubMed1989

Expression of raf oncogenes activates the PEA1 transcription factor motif.

PEA1 (AP1) motif transcription enhancer activity was stimulated by v-raf and more efficiently by activated c-raf-1 or A-raf than by their normal counterparts, in agreement with a role for PEA1 in transformation by raf. Mutations in the ATP-binding site of v-raf prevented activation, suggesting that phosphorylation is somehow required.

Adenosine Triphosphate↗

PubMed1988

v-jun is a transcriptional activator, but not in all cell-lines.

The recently isolated v-jun oncogene encodes a protein with sequence homology to the transcription factor AP1, as well as a similar DNA binding specificity. We show, by expressing v-jun in F9 embryocarcinoma cells, that v-jun is also a transcriptional activator. However, v-jun expression does not activate transcription in several other cell-lines, suggesting that cell-specific factors are required for v-jun activity.

Animals↗

PubMed1988

A Harvey-ras responsive transcription element is also responsive to a tumour-promoter and to serum.

The ras oncogenes are implicated in the onset of some human tumours, and in cellular proliferation and terminal differentiation. The ras proteins are plasma membrane bound transducers of signals between the outside of the cell and unknown targets in the cell. Identifying these targets and understanding how they are regulated will have a major impact on our understanding of the molecular basis of transformation. We have already shown that c-Ha-ras and the tumor promoter TPA (12-o-tetradecanoyl phorbol-13-acetate) can activate a transcriptional enhancer. We now report the identification of a short sequence in the polyoma virus (Py) enhancer which mediates Ha-ras activation, and show that this sequence (ras responsive element, RRE) also mediates activation by TPA and serum. This responsive element is a specific binding-site for the mouse transcription factor PEA1 (ref. 4 and below) and for the jun oncogene (ref. 5 and M. Karin, personal communication). These results are in keeping with a role for ras protein in signal transduction from outside the cell to a transcription factor in the nucleus, through protein kinase C. The striking similarity between RRE and DNA sequences present in the promoter regions of a number of transformation-related genes suggests that deregulated activation of RRE is a critical event in transformation.

Blood↗

PubMed1988

Transforming but not immortalizing oncogenes activate the transcription factor PEA1.

The transcription factor PEA1 (a homologue of AP1 and c-jun) is highly active in several fibroblast cell lines, compared to its low activity in a myeloma and an embryo-carcinoma (EC) cell line. Serum components are essential to attain these high levels of PEA1 activity in fibroblasts. This serum requirement is abrogated by transformation with the oncogenes c-Ha-ras, v-src and polyoma middle T (Py-MT) but not by immortalization with polyoma large T (Py-LT), v-myc, c-myc or SV40 large T (SV40T). Expression in myeloma cells of the same transforming oncogenes, as well as v-mos and c-fos, activates PEA1, whereas expression of the same immortalizing oncogenes and EIA does not. These results suggest that a common target for transforming oncogenes is PEA1. Serum components have no effect on PEA1 activity in the myeloma and EC cell lines. In contrast, retinoic acid treatment of F9 EC cells augments PEA1 activity. These results suggest that transforming oncogene expression compensates for the absence of cell type-specific factors which are required to activate PEA1. Activation of PEA1 may lead to altered transcription of a set of transformation-related genes.

Antigens, Polyomavirus Transforming↗

PubMed1988

Negative and positive factors determine the activity of the polyoma virus enhancer alpha domain in undifferentiated and differentiated cell types.

The host range of polyoma virus is dependent upon the activity of its enhancer, which is inactive in undifferentiated embryonal carcinoma cells, such as F9 cells, and is active after their differentiation. We show here that the activity of the alpha domain of the polyoma virus enhancer displays a similar cell-specificity and inducibility as does the whole enhancer. We present evidence to show that its activity is determined by the balance between the activities of two factors, PEA2, a labile repressor, and PEA1, an inducible positive factor that we have characterized previously. Changes in repressor activity help account for the increase in alpha-domain activity after differentiation of F9 cells. These results suggest that PEA2 is crucial in the regulation of viral gene expression and perhaps more generally in the control of gene expression during differentiation.

Animals↗

PubMed1987

The c-Ha-ras oncogene and a tumor promoter activate the polyoma virus enhancer.

A c-Ha-ras oncogene, to a lesser extent the c-Ha-ras proto-oncogene, and the tumor promoter 12-O-tetradecanoylphorbol-13-acetate activate the inactive polyoma virus (Py) enhancer in a myeloma cell line and the partially active Py enhancer in NIH 3T3 fibroblasts, but have no effect on the active Py enhancer in LMTK- fibroblasts. In addition, c-Ha-ras can stimulate the inactive Py enhancer in embryonal carcinoma F9 cells. c-Ha-ras activation in embryonal carcinoma cells does not appear to involve reversal of "E1A-like" inhibition of the enhancer. We suggest that modulation of cellular enhancer activity could play a key role in tumorigenesis by oncogenes.

Animals↗

PubMed1987

Negative regulation contributes to tissue specificity of the immunoglobulin heavy-chain enhancer.

We have identified in and around the immunoglobulin heavy-chain enhancer two apparently distinct negative regulatory elements which repress immunoglobulin H enhancer, simian virus 40 enhancer, and heterologous promoter activity in fibroblasts but not in myeloma cells. We propose that in nonlymphoid cells, negative regulatory elements prevent activation of the immunoglobulin H enhancer by ubiquitous stimulatory trans-acting factors.

Animals↗

PubMed1986

B-lymphocyte targeting of gene expression in transgenic mice with the immunoglobulin heavy-chain enhancer.

A hybrid gene containing rabbit beta-globin structural sequences (-9 to +1650), and a chicken conalbumin gene promoter (+62 to -102) in the place of the beta-globin promoter (upstream from -9), was inactive in 5 different transgenic mouse line. Adding the mouse immunoglobulin heavy-chain (IgH) enhancer to this construction specifically stimulated expression in B-cells. These results show that IgH enhancer is specifically active in B-cells. Expression of the hybrid gene was low compared to the endogenous immunoglobulin heavy and light-chain genes. Substituting the mouse immunoglobulin kappa light-chain gene (Ig kappa) promoter (+4 to -800) for the heterologous conalbumin promoter was not sufficient to restore gene expression to level of the endogenous genes. In addition to the reproducible B cell expression, we also found inheritable unexpected expression in certain tissues, which varied from line to line.

Animals↗

PubMed1986

The immunoglobulin heavy-chain B-lymphocyte enhancer efficiently stimulates transcription in non-lymphoid cells.

The mouse immunoglobulin heavy-chain (IgH) B-lymphocyte enhancer stimulates transcription from heterologous promoters 20- to 40-fold when transfected into several non-lymphoid cell lines. Stimulation in B-lymphocyte melanoma cell-lines is only about 5--10 times better. A central sequence is equally active in both cell types, whilst flanking sequences, on either side of the common enhancer sequences, specifically stimulate transcription in myeloma cells. These results suggest that there are factors in non-lymphoid cells that can interact with the IgH enhancer to stimulate transcription.

Animals↗

PubMed1986

The immunoglobulin heavy chain enhancer is stimulated by the adenovirus type 2 E1A products in mouse fibroblasts.

In contrast with our previous results (Hen, R., Borrelli, E. & Chambon, P. (1985) Science 230, 1391-1394), which demonstrated that the mouse immunoglobulin heavy chain transcriptional enhancer is repressed in lymphoid cells by the products of the adenovirus type 2 E1A transcription unit, we show here that these products activate the same enhancer in mouse fibroblast L cell lines that contain stably integrated copies of a recombinant in which the enhancer is inserted upstream from the chicken conalbumin promoter. In addition, competition experiments suggest that the activity of the heavy chain enhancer may be repressed by a trans-acting factor in mouse L cells. We speculate that the E1A products may prevent the action of this cellular repressor in these cells.

Adenovirus Early Proteins↗

PubMed1984

Short and long range activation by the SV40 enhancer.

Activation of transcription by the SV40 enhancer decreases in an apparently biphasic manner when DNA sequences are interposed between the SV40 enhancer and either the homologous SV40 early or the heterologous conalbumin promoter elements. With increasing lengths of short DNA fragments (up to about 150 bp) activation of transcription decreases to less than 10% of the maximum. This short range effect is observed for both the SV40 early and conalbumin promoter elements and for either orientation of the SV40 enhancer. With the conalbumin promoter, increasing the length of the interposing DNA to 275 bp decreases activation to approximately 4%. Larger inserts, of 650 or 3737 bp, lead to an activation of 0.5%. However, in these recombinants, transcription is still activated at least 10 fold compared to an enhancerless recombinant. The implication of these results is discussed.

Chromosome Mapping↗