Both products of the fosB gene, FosB and its short form, FosB/SF, are transcriptional activators in fibroblasts.
We demonstrate that a member of the fos family, the fosB gene, gives rise to two transcripts by alternative splicing of exon 4, generating two proteins, FosB of 338 amino acids and a short form, FosB/SF, which contains the DNA binding and dimerization domains but not the 101 amino acids of the C terminus. FosB/SF activates an AP-1-chloramphenicol acetyltransferase construct in NIH 3T3 cells, as determined by transient and stable transfections, although more weakly than does FosB. In contrast to FosB, FosB/SF has lost its ability to repress the dyad symmetry element of the c-fos gene. FosB/SF when expressed in excess to FosB can downmodulate the activity of FosB. Constitutive expression of high levels of FosB/SF in NIH 3T3 cells has no significant inhibitory effect in the induction of cell proliferation or cell cycle progression, indicating that FosB/SF is not a negative regulator of cell growth. This conclusion is further confirmed by the observation that the majority of the Jun molecules are complexed with FosB/SF in the FosB/SF-overexpressing cells.
Department of Molecular Biology, Bristol-Myers Squibb Pharmaceutical Research Institute, Princeton, New Jersey 08543-4000.
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Dobrazanski
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Noguchi
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Kovary
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Rizzo
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Lazo
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D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D002455:Cell Division; D015500:Chloramphenicol O-Acetyltransferase / Q000235:genetics / Q000378:metabolism; D005091:Exons; D005347:Fibroblasts / Q000166:cytology / Q000502:physiology; D016762:Genes, fos; D005822:Genetic Vectors; D051379:Mice; D008969:Molecular Sequence Data; D009841:Oligonucleotides; D010957:Plasmids; D016133:Polymerase Chain Reaction; D014176:Protein Biosynthesis; D016760:Proto-Oncogene Proteins c-fos / Q000235:genetics*; D012326:RNA Splicing; D015534:Trans-Activators / Q000235:genetics*; D014158:Transcription, Genetic; D015533:Transcriptional Activation; D014162:Transfection
D009841:Oligonucleotides; D016760:Proto-Oncogene Proteins c-fos; D015534:Trans-Activators; D015500:Chloramphenicol O-Acetyltransferase