CBL440 Sigma-AldrichAnti-c-Fos Antibody

We have investigated the sequences that are necessary and sufficient for the induction of the c-fos gene by serum, TPA or PDGF in different cell types. The dyad symmetry element (DSE) is a regulatory element of the c-fos gene previously shown to be required for induction of c-fos transcription by serum. We show that the DSE is also necessary for the induction of c-fos by either TPA or PDGF in NIH3T3 cells. We also show that in NIH 3T3 cells the DSE is sufficient to confer inducibility on a heterologous promoter, the beta-globin promoter, when serum provides the stimulus. However, it is not sufficient when either TPA or PDGF is the inducer. This suggests a requirement in 3T3 cells for cooperating sequence elements for TPA or PDGF induction but not for serum. Interestingly, the need for cooperating elements for TPA induction is abolished in HeLa cells since the DSE alone is sufficient for TPA inducibility of the beta-globin promoter in these cells. Thus, the highly transformed HeLa cell line displays diminished sequence requirements for TPA induction. We discuss the possibility that mutations which diminish the stringent transcriptional control of protooncogenes such as c-fos may contribute to the transformed state.

Increased but transient expression of the proto-oncogene c-fos has been recently reported in metrazol and kindling-induced seizures. Here we tested whether kainic acid-induced status epilepticus may result in a long-term increase of this oncogene. A specific pattern of immunoreactive c-fos material was observed with the development of the seizures. Intense labeling first appeared in the dentate gyrus of the hippocampus and the entorhinal cortex. Pyramidal cell layer CA3, CA4 and CA1 as well as other limbic structures were then positively stained during status epilepticus. In addition, the duration of c-fos expression was different according to the anatomical sites. In the dentate gyrus labeling did not exceed 4-5 h whereas the pyramidal cell layer CA1 exhibited increased c-fos expression for as long as 24 h. Here we propose that c-fos which has been related to growth and differentiation in previous studies, could be involved in processes inducing long-term plastic alterations in the limbic system.

The mRNA levels of two proto-oncogenes, c-fos and c-myc, were determined in human foreskin fibroblasts exposed to epidermal growth factor (EGF) or platelet-derived growth factor (PDGF) in a serum-free, defined medium (MCDB 104). Untreated, quiescent cells were found to have low or undetectable levels of c-fos and c-myc mRNA. Within 10 min after the addition of EGF or PDGF the c-fos mRNA level increased, reached a peak at 30 min, and then declined to the control level after 60 min. The level of c-myc mRNA increased somewhat later and peaked after 8 h in cultures treated with either of the growth factors. The c-myc mRNA level remained elevated throughout the 24 h of investigation. The concentrations of EGF and PDGF required for a maximal effect on c-fos or c-myc expression were found to be similar to those that give maximal effect on cell proliferation. Both c-fos and c-myc mRNA expression were super-induced by the addition of cycloheximide. The addition of neutralizing PDGF antibodies to cultures that had received PDGF 4 h earlier inhibited the subsequent increase in the c-myc mRNA level, indicating that the effect of PDGF on c-myc expression is not caused by a "hit and run," mechanism. Density-inhibited cells responded to EGF and PDGF by an increase in c-fos and c-myc mRNA levels in the absence of any mitogenic response. The present results conform to the view that the c-fos and c-myc proto-oncogenes may be important (or necessary) but not sufficient for the initiation of DNA synthesis. Moreover, the finding that both EGF and PDGF increase c-fos and c-myc expression supports our previous suggestion that these two growth factors may in part act via a common intracellular pathway in the prereplicative phase of human fibroblasts.

The complete nucleotide sequence of the c-fos(human) gene, the human cellular homolog of the oncogene (v-fos) of Finkel-Biskis-Jinkins murine osteosarcoma virus, has been determined. The c-fos(human) gene contains four discontinuous regions when compared with the v-fos gene. Three of the discontinuities are flanked by sequences characteristic of introns, while the fourth discontinuity is due to a deletion of 104 base pairs in the v-fos gene. As a consequence of the deletion, the predicted c-fos(human) and v-fos gene products differ at their carboxyl termini. Transcripts of 2.2 kilobases from the c-fos(human) gene have been identified in human cells. The sizes of these transcripts are in close agreement with the size expected from the nucleotide sequence after removal of introns.