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Biomedical subjects

C Wasylyk

Publications and source records attributed to C Wasylyk.

31 records · Page 2Linked to original sources
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↗
PubMed1984

A novel eukaryotic promoter element: the simian virus 40 72 base pair repeat.

Using both clones of mouse LMTK- cells cotransformed with various chimeric conalbumin promoter simian virus 40 (SV40) early gene recombinants and the herpes thymidine kinase gene, and HeLa cells transfected with the same chimeric recombinants, we show that the SV40 72 base pair (bp) repeat sequence is a bidirectional potentiator of initiation of transcription from adjacent T-A-T-A box-dependent and -independent start sites. These results are consistent with our previous model based mainly on the results of T antigen gene expression assays that the 72-bp repeat acts as a bidirectional entry site for RNA polymerase B. We also show that the conalbumin T-A-T-A box is an important element for efficient and accurate in vivo initiation of transcription.

Conalbumin↗
PubMed1983

Transcription from the SV40 early-early and late-early overlapping promoters in the absence of DNA replication.

Transcription for a hybrid SV40 promoter-beta globin coding sequence recombinant initiates from both early-early (EE) and late-early (LE) SV40 start sites (EES and LES) in the absence of DNA replication. The 72-bp repeat is essential to potentiate the elements of the two overlapping EE and LE promoters (EEP and LEP). Two current models, which can account for the EE to LE shift in RNA chain initiation during the SV40 replication cycle, are that LE transcription is linked to replication and occurs on newly replicated DNA molecules or that there are two promoter elements, a stronger EEP and a weaker LEP, T antigen repressing the EEP late in infection. Our results support the second model. A 5'-TATTTAT-3' to 5'-TATCGAT-3' mutation in the putative SV40 TATA box decreases transcription from EES, increases transcription from LES, and inhibits DNA replication. Therefore, this element acts as a classical TATA box for transcription, and yet is also important for DNA replication.

Animals↗
PubMed1983

The SV40 72 bp repeat preferentially potentiates transcription starting from proximal natural or substitute promoter elements.

Activation of gene expression by the SV40 72 bp repeat was studied at the transcriptional level by quantitative S1 nuclease mapping of total RNA isolated from Hela cells transfected with chimeric conalbumin promoter-SV40 early gene recombinants. Our results demonstrate that, irrespective of its orientation, the 72 bp repeat is a potentiator of initiation of transcription from "TATA"-box-dependent and -independent "natural" or "substitute" promoter elements. In addition, we show that potential proximal promoter sequences are activated in preference to more distal ones. These results are consistent with the bidirectional entry site model for transcription activation by the 72 bp repeat.

Antigens, Viral↗