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P Angel

Publications and source records attributed to P Angel.

At least 55 records · Page 3Linked to original sources
PubMed1995

Stimulation of c-Jun activity by CBP: c-Jun residues Ser63/73 are required for CBP induced stimulation in vivo and CBP binding in vitro.

The CBP protein mediates PKA induced transcription by binding to the PKA phosphorylated activation domain of CREB. Here we show that CBP also stimulates the activity of both c-Jun and v-Jun in vivo. The CREB binding domain of CBP is sufficient to contact to c-Jun in vitro. When this domain of CBP is linked to the activation domain of VP16 and expressed in vivo it stimulates c-Jun dependent transcription. Deletion analysis of c-Jun indicate that the CBP binding site is within the N-terminal activation domain. Loss of binding to CBP in vitro correlates with severely reduced transactivation capacity in vivo. Mutation of Ser63/73 in c-Jun, or the corresponding position in v-Jun (Ser36/46) leads to reduced binding to CBP in vitro and abolishes augmentation of transcription in vivo. These data are consistent with a mechanism by which CBP acts as a co-activator protein for Jun dependent transcription by interacting with the Jun N-terminal activation domain.

Binding Sites↗
PubMed1995

c-jun expression and growth stimulation in human ovarian carcinoma cell lines following exposure to cytokines.

We evaluated the effects of recombinant human G-CSF, rhGM-CSF, rhM-CSF and rhIL-1 alpha on proliferation and regulation of c-jun gene expression in 4 human ovarian-carcinoma (HOC) cell lines, NIH:OVCAR-3, SK-OV-3, HEY and BG-1, and in one primary ovarian tumor in vitro. The cytokines were administered in concentrations of 0.1 U/ml to 1000 U/ml. Cell growth was measured by crystal-violet- and thiazolyl-blue(MTT)-based cell counts. c-jun transcripts were measured by the solution hybridization/RNAse protection assay. RhM-CSF and rhGM-CSF showed no growth stimulation of any of the 5 cell lines tested. Results from exposure to rhG-CSF were different. The cell lines NIH:OVCAR-3, SK-OV-3, BG-1 and the primary ovarian tumor showed no proliferative response. A 2- to 3-fold increase in proliferation was observed in the HEY HOC cell line. rhIL-1 alpha led to growth stimulation in the BG-1 cell line, but showed an inhibitory effect in the NIH:OVCAR-3 cells. No effects of rhIL-1 alpha were observed in the remaining 2 cell lines nor in the primary ovarian tumor. Growth stimulation was accompanied by an increase in c-jun expression in the HEY cell line, and the BG-1 cell line. No alterations in c-jun expression were observed in the remaining 3 cell lines. Our results indicate that rhG-CSF or rhIL-1 alpha influence cell proliferation in 2 out of 5 human ovarian-tumor cell lines, accompanied by an increase in c-jun expression.

Cell Division↗
PubMed1995

Fos is an essential component of the mammalian UV response.

Mouse 3T3 fibroblasts lacking c-fos were employed to demonstrate an essential function of the UV-inducible transcription factor AP-1 (Fos/Jun) in the response to the cytotoxic effects of short-wavelength ultraviolet (UVC) radiation. Clonogenic survival and proliferation of cells lacking c-fos were drastically reduced following UV irradiation. This UV hypersensitivity manifests itself primarily in increased cell death, partly by apoptosis, and prolonged recovery time from UV-induced cell cycle arrest. Co-culture with wild-type cells did not ameliorate the hypersensitivity of mutant cells. Transcriptional induction of the c-Fos target genes collagenase I, stromelysin-1 and stromelysin-2 by UV is almost absent in cells lacking c-fos which correlates with a reduced UV induction of AP-1 DNA-binding and transactivation activity. The repair of UV-induced DNA lesions was not affected, as shown by unscheduled DNA synthesis and host cell reactivation assays. These data demonstrate that c-Fos is involved in a novel protective function other than DNA repair against the harmful consequences of UVC.

3T3 Cells↗
PubMed1995

Structural organization and chromosomal localization of the mouse collagenase type I gene.

A clone containing genomic sequences of part of the murine collagenase type 1 (MMP-1) gene was isolated. It contains exons 1-6 encoding all the domains required for collagenase function and 9 kb of 5'-flanking sequences. The gene organization and exon/intron borders are highly similar to the already described human and rabbit MMP-1 genes. However, neither the intron sequences, nor the promoter region up to position -660 exhibit significant sequence homologies with rabbit and human MMP-1, except for an AP-1-binding site and two PEA-3 consensus sequences. Binding studies in vitro revealed that the AP-1-binding site is recognized by Fos/Jun heterodimers with very high affinity. By in situ hybridization the mouse MMP-1 gene was located to the A1-A2 region of chromosome 9 in proximity to the curly whiskers (cw) locus. Based on the lack of sequence homologies of the promoter and intron regions, and since the chromosomal localization of the mouse and human MMP-1 genes may not be syntenic, these data strongly support previous suggestions that the MMP-1 genes from mouse, compared with rabbit and human, have evolved from different ancestral genes. The presence of the AP-1- and PEA-3- binding sites in all mammalian MMP-1 genes isolated so far, may, however, suggest evolutionary selection for common regulatory mechanisms of MMP-1 transcription.

3T3 Cells↗
PubMed1995

ATF-2 is preferentially activated by stress-activated protein kinases to mediate c-jun induction in response to genotoxic agents.

The major regulators of the c-jun promoter are ATF-2 and c-Jun. They act as pre-bound heterodimers on two 'AP-1-like' sites, and are preferentially addressed by different types of extracellular signals. The transactivating potential of ATF-2 is stimulated to a higher extent than that of c-Jun by a broad group of agents causing DNA damage and other types of cellular stress, such as short-wavelength UV, or the alkylating compounds N-methyl-N'-nitro-N-nitroso-guanidine (MNNG) or methylmethanesulphonate (MMS). In contrast, treatment with the phorbol ester TPA preferentially enhances c-Jun-dependent transactivation but does not affect ATF-2. Accordingly, UV and MMS but not TPA induce c-jun transcription in F9 cells, which express ATF-2, but not c-Jun. Stimulation of ATF-2-dependent transactivation by genotoxic agents requires the presence of threonines 69 and 71 located in the N-terminal transactivation domain. These sites are the target of p54 and p46 stress-activated protein kinases (SAPKs) which bind to, and phosphorylate ATF-2 in vitro. However, p46 and p54 kinase activity is not increased by phorbol ester, which strongly suggests that the protein kinase phosphorylating c-Jun in response to TPA is distinct from SAPKs and does not act on ATF-2. Our data demonstrate that distinct signal transduction pathways converge at c-Jun/ATF-2, whereby each subunit is individually addressed by a specific class of protein kinases. This allows fine tuned modulation of c-jun expression by a large spectrum of extracellular signals.

Activating Transcription Factor 2↗
PubMed1995

Modulation of AP-1/ATF transcription factor activity by the adenovirus-E1A oncogene products.

The proteins encoded by early region 1 A (E1A) of human adenoviruses (Ad) modulate the expression of both adenovirus genes and various host cell genes. With these transcription-regulating properties the E1A proteins redirect the cell's metabolism, which enables them to induce oncogenic transformation in rodent cells. The E1A proteins modulate transcription by interacting both with gene-specific and general cellular transcription factors. Various members of the AP-1 and ATF/CREB families of transcription factors are targets for E1A-dependent regulation, including cJun, the protein product of the c-jun proto-oncogene. The E1A proteins modulate cJun-dependent transcription both positively and negatively, and affect the activity as well as the expression levels of cJun. By increasing the phosphorylation status of cJun, E1A can stimulate transcription regulated by cJun/ATF2 heterodimers. In contrast, E1A inhibits the expression of various metalloproteases by interfering with the DNA-binding capacity of cJun/cJun and cJun/cFos dimers, which might involve the association of E1A with the putative transcriptional coactivator p300. Since the ability of E1A to alter cJun-dependent transcription correlates with its transforming capacity, interference with cJun-dependent transcription may be an essential step in E1A-induced transformation.

Adenoviridae↗
PubMed1995

Transcriptional control of human papillomavirus type 18 oncogene expression in different cell lines: role of transcription factor YY1.

Binding of YY1 to the proximal fragment of the human papillomavirus type 18 (HPV-18) upstream regulatory region (URR) activates the oncogene expression of HPV-18 in HeLa cells, whereas in HepG2 cells this expression is repressed by YY1. In the present transient transfection study, we analyze the regulation of the HPV-18 URR by YY1 in an extended number of cell lines. Except for HeLa cells, YY1 represses or does not influence oncogene expression in all cell lines tested. In HeLa cells the activation of viral oncogene expression by YY1 is caused by the functional interplay between YY1 and a factor binding to the newly identified "switch region" of the HPV-18 URR. In this work we show that in HeLa cells, a 22 bp region located between the "switch region" and the promoter proximal fragment contributes to the modulation of the activity of YY1 and, in addition, regulates HPV-18 promoter activity independently of YY1.

Base Sequence↗
PubMed1995

The glucocorticoid receptor synergizes with Jun homodimers to activate AP-1-regulated promoters lacking GR binding sites.

Jun/Fos (AP-1) and steroid hormone receptors (SHR) are distinct families of transcription factors that convert extracellular signals into long-term genetic responses. Despite clear differences in their modes of activation and DNA binding specificities, a regulatory cross-talk between AP-1 and SHR such as the glucocorticoid receptor (GR), has been established. Here, we show that the hormone-activated GR negatively or positively modulates the expression of AP-1-dependent genes, depending on the subunits of the dimeric AP-1 complex. This type of regulation does not depend on the presence of a GR binding site in the promoter and is mediated through the DNA binding domain of Jun. Since individual subunits of AP-1 exhibit small differences in sequence specificity, specific subsets of AP-1-dependent genes may be regulated by steroid hormones in different directions.

Animals↗
PubMed1995

A switch region determines the cell type-specific positive or negative action of YY1 on the activity of the human papillomavirus type 18 promoter.

YY1 is a zinc finger transcription factor which acts as either a repressor or an activator dependent on the promoter context. YY1 is a potent activator of the genuine human papillomavirus type 18 (HPV-18) upstream regulatory region (URR) in HeLa cells, which are known for high-level expression of the HPV-18 early genes. The activating activity of YY1 is dependent on the presence of a newly identified switch region located upstream of the YY1 binding site. Deletion of this region causes YY1 to act as a repressor of HPV-18 promoter activity. In vivo footprinting of the HPV-18 URR and an in vitro electrophoretic mobility shift assay identified proteins binding to the switch region. Site-directed mutagenesis of the switch region and YY1 binding sites suggests that these two regions work in concert to yield high-level HPV-18 URR activity in HeLa cells but not in HepG2 cells, where HPV-18 is almost inactive. These data identified a novel mode of cell type-specific regulation of HPV-18 promoter activity by positive or negative action of YY1, determined by the switch region binding factor(s).

Base Sequence↗
PubMed1995

Expression of interstitial collagenase during skeletal development of the mouse is restricted to osteoblast-like cells and hypertrophic chondrocytes.

We determined the expression pattern of the matrix metalloproteinase interstitial collagenase (MMP-1) during mouse embryo development using in situ hybridization and immunohistochemistry. Localized MMP-1 mRNA was first detected at 14.5 days postconceptus. The spatial and temporal expression was restricted to areas of endochondral and intramembranous bone formation, such as in the mandibula, maxilla, clavicle, scapula, in the vertebrae, and in the dorsal, but not the ventral part of the ribs. The highest levels of MMP-1 transcripts and MMP-1 protein were found in the metaphyses and diaphyses of the long bones. MMP-1 was expressed by hypertrophic chondrocytes and by osteoblastic cells localized along the newly formed bone trabeculae. No expression was detected in osteoclasts. Two other related members of the MMP family, stromelysin-1 (MMP-3) and stromelysin-2 (MMP-10), were not expressed during days 7.5 and 16.5 of mouse embryogenesis. The tissue-specific expression of MMP-1 and the exclusive ability of interstitial collagenase to digest native collagen of types I, II, III, and X, the major components of bone, cartilage, and tendon, strongly suggests an important and specific function of this enzyme in bone development and remodeling.

Animals↗
PubMed1994

Phenotypic alterations in fos-transgenic mice correlate with changes in Fos/Jun-dependent collagenase type I expression. Regulation of mouse metalloproteinases by carcinogens, tumor promoters, cAMP, and Fos oncoprotein.

Using specific cDNAs isolated from mouse fibroblasts we determined tissue-specific expression of different matrix metalloproteinase genes: both stromelysin-1 and collagenase IV are highly expressed in heart and lung, whereas collagenase I is expressed most abundantly in skeletal muscle, kidney, and bone. High basal level expression of stromelysin-2 is found in heart and kidney. Like in man and rat, the expressions of collagenase I, stromelysin-1, and stromelysin-2 are regulated by the tumor promoter 12-O-tetradecanoyl-phorbol 13-acetate and by UV irradiation, but not by cAMP. In contrast, the expression of the 72-kDa collagenase IV is not affected by either stimuli. We and others have shown previously that under cell culture conditions, the regulation of human collagenase I is regulated by the transcription factor Fos/Jun (AP-1). Here we show that in c-fos transgenic mice transcription of collagenase I is induced in thymus, spleen, and, most dominantly, in bone upon overexpression of Fos. Neither collagenase IV nor stromelysin-1 or stromelysin-2 expression is affected by c-Fos. The sites of induced collagenase I expression correlate with the sites of Fos-induced long-term cellular alterations in transgenic mice including bone remodeling and T cell development. In fact, in the developing bone tumors strongly enhanced levels of collagenase I transcripts were detectable. These results identify collagenase I as a Fos-regulated gene in vivo and suggest a possible role for Fos/Jun heterodimers in establishing the pathological phenotype of c-fos transgenic mice.

3T3 Cells↗
PubMed1994

Binding of promoter-associated AP-1 is not altered during induction and subsequent repression of the c-jun promoter by TPA and UV irradiation.

Rapid transient induction of the human c-jun proto-oncogene by 12-O-tetradecanoylphorbol-13-acetate (TPA) and UV irradiation requires the presence of two cis-acting elements, Jun1 and Jun2. Using dimethyl sulfate (DMS) genomic footprinting, in vivo, all protein binding sites in the c-jun promoter, including Jun1 and Jun2, are already fully occupied before induction and the protein--DNA contacts are unchanged during gene activation by TPA and UV and subsequent repression. In vitro binding studies suggest that both sites are recognized with high affinity by protein complexes containing cJun and ATF-2. Jun1 is also recognized by complexes containing Fos and Jun in vitro, but with only a very low affinity. The binding of Jun/ATF-2-containing complexes to Jun1 or Jun2 is not affected during early and late time points after induction. Transcriptional shut-off is caused by neither a loss of binding of an activating protein nor by additional binding of a putative repressor. The lack of detectable changes in DNA binding and factor composition strongly suggests that transcriptional activation and subsequent inactivation of c-jun promoter activity by TPA or UV is mediated by post-translational modifications of prebound cJun and possibly ATF-2. Such pre-formed structures on the promoter could be a general requirement for the rapid and transient transcriptional responses of immediate-early genes to extracellular signals.

Base Sequence↗
PubMed1993

Gene structure and expression analysis of the epidermal growth factor receptor, transforming growth factor-alpha, myc, jun, and metallothionein in human ovarian carcinomas. Classification of malignant phenotypes.

This study reports the structure and expression rates of genes of the transforming growth factor-alpha (TGF-alpha) signal transduction pathway (TGF-alpha, epidermal growth factor receptor [EGF-R], jun, myc, and metallothionein [MT]) in 47 specimens of ovarian cancer and 21 nonmalignant tissues. The objective was to establish a direct correlation between the genetic activities and the malignant phenotype of the ovarian cancer. The Southern blot technique identified four samples with myc amplification and two with rearranged EGF-R genes. By using the S1 nuclease assay, the analysis of myc transcription showed a similar use of both promotors. Although the size of the investigated transcripts was unaltered, significant differences in the transcription rates were noticed in malignant tissue probes (using northern blot analysis and RNAase protection assay). The following results of messenger RNA analysis in ovarian cancer were observed: EGF-R, negative in 25%, low in 65%, and strongly positive in 10%; TGF-alpha, negative in 34%, low in 36%, and strongly positive in 30%; myc, negative in 8%, low in 64%, and strongly positive in 28%; jun, negative in 4%, low in 58%, and strong in 38%; and MT, low in 80% and strongly positive in 20%. In most nonmalignant tissues studied, no or only a low expression of TGF-alpha, EGF-R, and myc. was found. A comparison of these messenger RNA results with the clinical data from tumors showed four different subgroups of ovarian carcinomas. The results of chemotherapy were known in 32 cases. Tumors with negative or low expression rates of all investigated genes did not respond to chemotherapy; 13 of 18 tumors with high expression rates did respond. Additional signal transduction chains distinct from the TGF-alpha pathway, however, are likely to influence both the expression and activity of transcription factors and MT.

Adult↗
PubMed1993

Heterodimer formation of cJun and ATF-2 is responsible for induction of c-jun by the 243 amino acid adenovirus E1A protein.

The adenovirus E1A proteins differentially regulate AP-1-responsive genes. Collagenase and stromelysin are repressed by E1A, whereas the expression of c-jun is elevated. Inhibition of collagenase has been found to be exerted through the consensus AP-1 binding site TGAGTCA. Here we show that the distal AP-1 binding site in the c-jun promoter, the jun2TRE (TTACCTCA), is the decisive element of this promoter in mediating the positive response to the 243 amino acid E1A product. In vitro binding studies revealed that, in contrast to the consensus AP-1 site which is preferentially targeted by dimers composed of the Jun and Fos families, the jun2TRE binds heterodimers composed of cJun and ATF-2(-like) proteins. Since stimulation of c-jun transcription is a function of the transforming domain of E1A encoded by conserved region 1, cJun--ATF-2 may be one of the effector factors involved in transformation. The data further suggest that E1A can distinguish between cJun--cJun and cJun--ATF-2 in imposing opposite states of activity.

3T3 Cells↗
PubMed1993

UV-induced activation of AP-1 involves obligatory extranuclear steps including Raf-1 kinase.

Irradiation of cells with ultraviolet light (UV) leads to modifications of c-Jun resembling those elicited by phorbol esters or oncogenes, and to enhanced transcription of AP-1-dependent genes. The UV-induced signal also triggers activation of Raf-1 and MAP-2 kinases. A dominant-negative Raf-1 kinase mutant strongly interferes with both phorbol ester and UV-induced AP-1 activation, indicating obligatory involvement of identical components in cytoplasmic signal transduction. Thus, from a presumably nuclear site of energy absorption, a signal needs to be transmitted to the cytoplasm in order to achieve activation of a nuclear transcription factor. Further, signals elicited from different primary sites merge prior to or at the level of activation of Raf-1 kinase.

Base Sequence↗
PubMed1993

Adenovirus E1A negatively and positively modulates transcription of AP-1 dependent genes by dimer-specific regulation of the DNA binding and transactivation activities of Jun.

Adenovirus E1A proteins inhibit expression of the collagenase gene but activate expression of the c-jun gene. Both effects are mediated by TPA-responsive elements (TREs), the binding sites for members of the AP-1 transcription factor family. By a process that is independent of the retinoblastoma gene product, E1A distinguishes between different AP-1 factors: in vivo binding of Jun/Jun homodimers and Jun/Fos heterodimers to the collagenase TRE is totally blocked by E1A while, in contrast, there is no inhibition of Jun/ATF-2 binding to the TRE sequences in the c-jun promoter. Altered phosphorylation of the DNA binding domain of cJun is not involved in the inhibition of cJun/cJun and cJun/cFos binding. E1A does, however, cause hyperphosphorylation of the transactivation domain of cJun, which is likely to be responsible for the enhanced c-jun transcription by E1A mediated through cJun/ATF-2 heterodimers.

Activating Transcription Factors↗
PubMed1993

Cross-coupling of the NF-kappa B p65 and Fos/Jun transcription factors produces potentiated biological function.

NF-kappa B and AP-1 represent distinct mammalian transcription factors that target unique DNA enhancer elements. The heterodimeric NF-kappa B complex is typically composed of two DNA binding subunits, NF-kappa B p50 and NF-kappa B p65, which share structural homology with the c-rel proto-oncogene product. Similarly, the AP-1 transcription factor complex is comprised of dimers of the c-fos and c-jun proto-oncogene products or of closely related proteins. We now demonstrate that the bZIP regions of c-Fos and c-Jun are capable of physically interacting with NF-kappa B p65 through the Rel homology domain. This complex of NF-kappa B p65 and Jun or Fos exhibits enhanced DNA binding and biological function via both the kappa B and AP-1 response elements including synergistic activation of the 5' long terminal repeat of the human immunodeficiency virus type 1. These findings support a combinatorial mechanism of gene regulation involving the unexpected cross-coupling of two different classes of transcription factors to form novel protein complexes exhibiting potentiated biological activity.

3T3 Cells↗