The CREB-binding protein (CBP) cooperates with the serum response factor for transactivation of the c-fos serum response element.
The serum response element is one of the major promoter elements of the immediate early response to extracellular signals. The serum response element includes two main binding sites for proteins: the Ets box, which binds p62(TCF), and the CArG box, which binds p67(SRF). These two proteins are direct targets for signal transduction pathways; p62(TCF) is a nuclear end point of the Ras/mitogen-activated protein kinase pathway, and p67(SRF) is targeted by the Rho/Rac small G-proteins. The mechanism by which the signal is further transduced from the transcription factors to the basal transcriptional machinery is poorly understood. Recent data have suggested that the cAMP-responsive element-binding protein (CREB)-binding protein, a transcriptional adaptor involved in the transactivation through a wide variety of enhancer elements, participates in p62(TCF) activity. We here show that the CREB-binding protein also cooperates in the process of transactivation by p67(SRF). Cotransfections of expression vectors for the CREB-binding protein increased the expression, in response to serum, of reporters under the control of the c-fos serum response element. Interestingly, the C-terminal moiety of the CREB-binding protein was not necessary to observe this effect. The cooperation did not require the Ets box in the serum response element, and the CArG box was sufficient, indicating that the CREB-binding protein is able to cooperate with p67(SRF) in the absence of an Ets protein. Co-immunoprecipitation experiments using cell extracts showed that p67(SRF) could be retained with antibodies directed against the CREB-binding protein, suggesting that the two proteins form a multimolecular complex in live cells. The physical interaction between p67(SRF) and the CREB-binding protein was further confirmed by two-hybrid assays in mammalian cells. Our results indicate that the CREB-binding protein cooperates with p67(SRF) and, thus, suggest that the serum response element is regulated by a multimolecular complex, which includes the CREB-binding protein, p67(SRF), and p62(TCF), with multiple interactions between the components of the complex.
Ramirez
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Laboratoire "Oncogénèse, Différenciation et Transduction du Signal," CNRS UPR 9079, Institut Fédératif sur le Cancer, 7 rue Guy Moquet, 94801 Villejuif, France.
Ait-Si-Ali
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S
Robin
P
P
Trouche
D
D
Harel-Bellan
A
A
Ait Si Ali
S
S
D016475:3T3 Cells; D000818:Animals; D001483:Base Sequence; D050882:CREB-Binding Protein; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism*; D008156:Luciferases / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000378:metabolism; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D050783:Proto-Oncogene Proteins c-ets; D026362:Serum Response Factor; D015534:Trans-Activators; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation
D004268:DNA-Binding Proteins; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D050783:Proto-Oncogene Proteins c-ets; D026362:Serum Response Factor; D015534:Trans-Activators; D014157:Transcription Factors; D008156:Luciferases; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse; D011505:Protein-Tyrosine Kinases