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T Curran

Publications and source records attributed to T Curran.

At least 181 records · Page 10Linked to original sources
PubMed1988

Fos and Jun bind cooperatively to the AP-1 site: reconstitution in vitro.

The protein products of the fos (Fos) and jun (Jun) proto-oncogenes have been shown to associate with a DNA element known as the transcription factor activator protein-1 (AP-1) binding site. Jun (previously known as the Fos-binding protein p39) and Fos form a protein complex in the nucleus. To investigate the nature of the association of Fos and Jun with the AP-1 site, and to determine the role of protein complex formation in DNA-binding, we have reconstituted the protein-protein and protein-DNA interactions in vitro using Fos and Jun synthesized in reticulocyte lysates. The Fos-Jun complex formed extremely rapidly in vitro and possessed similar, though not identical, chromatographic and sedimentation properties to the complex isolated from cell extracts. Jun exhibited a low level of AP-1 binding activity; however, this was evident only at high concentrations of DNA. Fos did not bind to the AP-1 site on its own; however, it acted cooperatively with Jun to give enhanced DNA-binding activity. The increased affinity of the Fos-Jun complex for DNA resulted from a stabilization of the protein-DNA complex. These data demonstrate a cooperative interaction between the protein products of two proto-oncogenes with a DNA element involved in transcriptional regulation.

Allosteric Regulation↗
PubMed1988

Activation of the transforming potential of the human fos proto-oncogene requires message stabilization and results in increased amounts of partially modified fos protein.

The requirements for activation of the transformation potential of the human c-fos proto-oncogene were investigated. Recombinant plasmids containing the Moloney murine leukemia virus long terminal repeat directing transcription of the c-fos coding region and either the authentic c-fos 3' untranslated region (UTR) or the 3' UTR from human c-myc were inefficient at inducing transformation. In contrast, a recombinant that substituted most of the c-fos 3' UTR with the 3' portion of the simian virus 40 T-antigen gene transformed cells well. This difference in transformation efficiency appeared to be due to significantly higher levels of fos mRNA and protein expressed from the transforming recombinant. This, in turn, was due to the much greater stability of its mRNA compared with those from the poorly transforming recombinants containing the c-fos or c-myc 3' UTR. Thus, the 3' UTR of the human c-fos mRNA is responsible for its rapid degradation and limits the steady-state levels of transcript and protein. Cells transformed by the activated human c-fos plasmids contained increased amounts of partially modified c-fos protein (c-Fos). This form of c-Fos turned over much more rapidly than the highly modified form of c-Fos induced by serum stimulation.

Animals↗
PubMed1988

fra-1: a serum-inducible, cellular immediate-early gene that encodes a fos-related antigen.

A set of proteins antigenically related to the c-fos protein (Fos) are induced by serum in fibroblasts. To isolate cDNA clones of genes encoding such proteins, a lambda gt11 expression cDNA library constructed from serum-stimulated rat fibroblasts was screened with antibodies raised against a hydrophilic region (amino acids 127 to 152) of Fos. One of the positive clones identified, termed fra-1 (Fos-related antigen) was characterized. It encoded a protein that shared several regions of extensive amino acid homology with Fos (including the region that showed similarity to both the yeast GCN4 regulatory protein and the protein encoded by the jun oncogene), although its nucleotide sequence was considerably diverged from that of the c-fos gene. Only a subset of the agents and conditions that activated c-fos also induced fra-1. Induction of fra-1 expression following serum stimulation was delayed compared with that of c-fos. However, like c-fos, fra-1 was induced rapidly by serum in the presence of protein synthesis inhibitors. Thus, a family of Fos-related, inducible genes are involved in the cellular immediate-early transcriptional response to extracellular stimuli.

Amino Acid Sequence↗
PubMed1987

The effects of phorbol ester and Ca ionophore on c-fos and c-myc expression and on DNA synthesis in human lymphocytes are not directly related.

Phorbol ester activates human lymphocyte proliferation as measured by [3H]thymidine incorporation and blast transformation. Phorbol ester and calcium ionophore A 23187 induce c-fos and c-myc expression in these cells as shown by the measure of the specific mRNA levels and of the c-fos nuclear protein amount. The combination of these two agents has a synergistic effect on c-fos but not on c-myc expression. Lymphocyte stimulation by phorbol ester for a short time induces c-fos and c-myc expression, but has no effect on [3H]thymidine incorporation. This result indicates that the induction of c-fos and c-myc expression is not sufficient to commit these cells to DNA synthesis.

Adult↗
PubMed1987

Mapping patterns of c-fos expression in the central nervous system after seizure.

A dramatic and specific induction of c-fos was observed in identifiable neuronal populations in vivo after administration of the convulsant Metrazole. This effect was time- and dose-dependent and was abolished by prior treatment with the anticonvulsant drugs diazepam or pentobarbital. About 60 minutes after administration of Metrazole, c-fos messenger RNA reached a maximum and declined to basal levels after 180 minutes. A further decrease below that in normal brain was observed before a return to basal levels after 16 hours. While Metrazole still elicited seizures during this period, reinduction of c-fos was largely refractory. At 90 minutes, c-fos protein was observed in the nuclei of neurons in the dentate gyrus, and in the pyriform and cingulate cortices. Subsequently, c-fos protein appeared throughout the cortex, hippocampus, and limbic system. Thus, seizure activity results in increased c-fos gene expression in particular subsets of neurons.

Animals↗
PubMed1987

Memories of fos.

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Animals↗
PubMed1987

Microinjection of transforming ras protein induces c-fos expression.

Microinjection of p21ras induced c-fos protein accumulation in three types of 3T3 cells. The induction was rapid and efficient and persisted for many hours. In addition, anti-ras antibody dramatically reduced c-fos accumulation after serum stimulation of injected cells. However, cells which expressed p21ras continuously did not maintain a high level of c-fos expression.

Animals↗
PubMed1987

Levels of fos, ets2, and myb proto-oncogene RNAs correlate with segregation of chromosome 11 of normal cells and with suppression of tumorigenicity in human cell hybrids.

The tumorigenicity in nude mice of human carcinoma-derived D98AH2 (D98) cells is suppressed when cell hybrids are made by fusing these cells with normal human diploid cells. Selection for hybrids that have segregated chromosomes results in the recovery of tumorigenic segregants. These segregants have all lost at least one copy of chromosome 11 of the diploid cell parent. Earlier we found that the parental D98 cells had detectable levels of mRNA specific for 13 of 21 proto-oncogenes examined. To determine if transregulation of proto-oncogenes by genes of the normal cell occurs in such hybrids, the steady-state levels of mRNA specific to 22 proto-oncogenes in the parental cells were compared with those of nontumorigenic D98 X human diploid hybrids as well as with those of their tumorigenic segregants and with the cells of the resulting tumors. The only chromosome consistently segregated in the latter was chromosome 11 of the diploid cell. fos and ets2 RNA levels and the amount of fos protein were consistently elevated in the segregants compared with amounts in the original hybrids. An unexpected finding was the inverse relationship for myb RNA that was barely detected in the parental D98 cells but was at least 10-fold elevated in hybrids that did not have segregated chromosomes compared with those that did. These patterns were evident in RNAs prepared from both subconfluent and confluent cell cultures. The findings suggest that genes of the normal cell parent can affect proto-oncogene expression. Whether the genes affecting fos, ets2, and myb RNA levels are on chromosome 11 and whether these alterations are causally related to the tumorigenic phenotype of the hybrid remain to be determined.

Animals↗
PubMed1987

Analysis of Fos protein complexes and Fos-related antigens by high-resolution two-dimensional gel electrophoresis.

Protein complexes containing the c-fos protein (Fos) and (Fos)-related antigens were isolated from serum-stimulated fibroblasts and from nerve growth factor plus benzodiazepine-treated pheochromocytoma (PC12) cells, and investigated by high-resolution two-dimensional gel electrophoresis. The results show that Fos is complexed with a basic 39-kDa protein (p39) in fibroblasts, and primarily with an acidic 40-kDa protein (p40) in PC12 cells. Whole cells lysates from both cell types contain p40, suggesting that the interaction of Fos and other cellular proteins is dependent on the differentiated state of the cell. In addition to p39 and p40, a heterogeneous population of polypeptides of approximately 48 kDa are present in Fos complexes isolated from non-denatured extracts of either cell type. These proteins may represent a minor class of Fos-binding proteins. Analysis of extracts prepared under denaturing conditions using antisera raised against a Fos peptide (amino acids 127-152) reveals a series of Fos-related antigens. These antigens are induced, some with a slower kinetics than Fos, in fibroblasts and PC12 cells. Thus, c-fos may represent a marker for a family of genes, some of which are antigenically related, that are part of an early cellular transcriptional response to diverse extracellular stimuli.

Animals↗
PubMed1987

Isolation and characterization of the c-fos(rat) cDNA and analysis of post-translational modification in vitro.

c-fos mRNA accumulates to a level of 0.2% of cellular poly(A)-containing RNA 45 min after treatment of rat pheochromocytoma (PC12) cells with 1 mM barium chloride. Several clones of the c-fos(rat) cDNA were isolated from a cDNA library constructed from this RNA population. Nucleotide sequence analysis of a full-length cDNA clone reveals striking conservation among the c-fos genes isolated from rat, mouse and human cells, and confirms the c-fos gene structure predicted from an analysis of c-fos genomic clones. Translation of an SP6-derived transcript of the c-fos(rat) cDNA in a messenger-dependent rabbit reticulocyte lysate yields the complete c-fos protein. It undergoes extensive post-translational modification in the lysate, particularly in the presence of additional cAMP. The c-fos protein synthesized in vitro appears to be phosphorylated by the cAMP-dependent protein kinase.

Amino Acid Sequence↗
PubMed1986

The Fos protein complex is associated with DNA in isolated nuclei and binds to DNA cellulose.

The properties of the viral and cellular fos proteins (Fos) were investigated as a first step toward understanding the function of the fos gene. Treatment of nuclei with salt and nonionic detergents solubilized a complex that contained Fos together with several other cellular proteins. The majority of the Fos protein complex was released from isolated nuclei incubated in the presence of deoxyribonuclease I or micrococcal nuclease but not with ribonuclease A, suggesting that Fos is associated with chromatin. This hypothesis is supported by the finding that Fos protein from native or denatured nuclear extracts exhibited DNA-binding activity in vitro. These results suggest that Fos is involved in the regulation of gene expression.

Adrenal Gland Neoplasms↗
PubMed1986

Expression of c-fos in NIH3T3 cells is very low but inducible throughout the cell cycle.

It has previously been shown that the c-fos proto-oncogene is rapidly and transiently induced following growth factor stimulation of quiescent NIH3T3 mouse fibroblasts. To investigate a possible role of c-fos in growth control mechanisms we have studied its expression and inducibility during the NIH3T3 cell cycle. Two major conclusions can be drawn from this analysis. First, expression of c-fos is not cell cycle-regulated, and is barely detectable in all phases of the cycle. Second, cells at different stages of the cell cycle (except for mitosis) are as sensitive to c-fos induction by growth factors as quiescent cells. These observations suggest that induction of the c-fos gene does not play a role during the continuous cycling of NIH3T3 cells, but they are fully compatible with the hypothesis that a function of c-fos may be associated with the induction of competence in fibroblasts. Through such a function c-fos may contribute to moving cells out of the quiescent state.

Animals↗
PubMed1986

The fos gene product undergoes extensive post-translational modification in eukaryotic but not in prokaryotic cells.

To investigate the properties of the fos oncogene, we have constructed bacterial and yeast vectors which express the entire fos-coded protein (Fos) and two C-terminal deletion products. In Escherichia coli, Fos proteins were expressed from the phage lambda pL promotor under the control of the temperature-sensitive lambda repressor. In vitro transcription/translation studies indicate that these vectors produce Fos proteins of the expected sizes. However, in vivo, Fos protein accumulation is observed only in hosts with the Lon- phenotype. In Saccharomyces cerevisiae, the fos gene was expressed from the PHO5 promoter which is induced under low-phosphate conditions. In contrast to the situation in E. coli, in which the heterologous proteins appeared as single major products when subjected to sodium dodecyl sulfate - polyacrylamide gel electrophoresis, the Fos proteins in S. cerevisiae displayed extensive Mr heterogeneity. Pulse-chase analyses indicated that this heterogeneity was a consequence of extensive post-translational modification. These modifications occurred to an equivalent extent on the products coded by the fos gene with C-terminal deletions and thus appear not to be controlled by the missing domain.

Animals↗
PubMed1986

Numbness of half of the tongue.

We report a case of intermittent compression of he lingual nerve due to sialolithiasis and presenting with episodic unilateral numbness of the tongue. Removal of the obstruction has relieved the patient of symptoms over a 21 month period to date.

Adult↗
PubMed1986

Barium modulates c-fos expression and post-translational modification.

The addition of exogenous barium ions to PC12 rat pheochromocytoma cells elicits a transient induction of the c-fos gene. Induction is antagonized by extracellular calcium and the dihydropyridine calcium channel blockers, and it is attenuated in the presence of calmodulin inhibitors. Thus, barium appears to enter the cell through a voltage-dependent calcium channel and, either directly or indirectly, interacts with calmodulin to stimulate c-fos expression. This property of barium is not shared by a range of di- and trivalent cations examined. Agents that induce the c-fos gene in PC12 cells may be divided into two broad categories. The first comprises polypeptide growth factors and phorbol esters, which give rise to a c-fos protein that undergoes extensive post-translational modification. The second, which comprises depolarizing agents and barium ions, acts via calcium channels and yields a c-fos protein that undergoes less extensive post-translational modification. These different forms of c-fos protein can be distinguished on the basis of their apparent molecular weights on sodium dodecyl sulfate/polyacrylamide gels.

Barium↗
PubMed1986

[Stimulation of human lymphocytes by phorbol acetate and a calcium ionophore induces an early transient expression of the c-fos oncogene followed by c-myc].

After stimulation of human lymphocytes by 12-0 tetradecanoyl phorbol acetate (TPA) and by the calcium ionophore A23187 an early transient expression of proto-oncogene fos followed by an expression of c-myc is observed, as has been described in rodent fibroblast stimulated by growth factors. This observation suggests a direct role of protein Kinase C and of calcium flux an the induction of cellular oncogenes fos and myc that may be associated with the early steps of activation and proliferation of lymphocytes.

Calcimycin↗
PubMed1985

Superinduction of c-fos by nerve growth factor in the presence of peripherally active benzodiazepines.

Alterations in proto-oncogene expression after stimulation of rat pheochromocytoma (PC12) cells by nerve growth factor (NGF) have been investigated. A specific stimulation of c-fos messenger RNA and protein was detected 30 minutes after treatment. This induction was enhanced more than 100-fold in the presence of peripherally active benzodiazepines. The effect was specific as very little change was observed in the levels of c-rasHa, c-rasKi, c-myc, and N-myc messenger RNA's. Under the conditions used here, NGF treatment ultimately results in neurite outgrowth, with a reduction or cessation of cell division. Thus, stimulation of the c-fos gene in this system appeared to be associated with differentiation and not with cellular proliferation. The effect of benzodiazepines was stereospecific and represents a novel action of these compounds at the level of gene expression.

Animals↗