Induction-independent recruitment of CREB-binding protein to the c-fos serum response element through interactions between the bromodomain and Elk-1.
Proliferative signals lead to the rapid and transient induction of the c-fos proto-oncogene by targeting the ternary complex assembled on the serum response element (SRE). Transactivation by both components of this complex, serum response factor (SRF) and the ternary complex factor Elk-1, can be potentiated by the coactivator CREB-binding protein (CBP). We report a novel interaction between the bromodomain of CBP, amino acids 1100-1286, and Elk-1. DNA binding and glutathione S-transferase pull-down assays demonstrate that binding requires Elk-1(1-212) but not the C-terminal transactivation domain. Competition and antibody controls show that the bromocomplex involves both SRF and Elk-1 on the c-fos SRE and uniquely Elk-1 on the E74 Ets binding site. Interestingly, methylation interference and DNA footprinting analyses show almost indistinguishable patterns between ternary and bromocomplexes, suggesting that CBP-(1100-1286) interacts via Elk-1 and does not require specific DNA contacts. Functionally, the bromocomplex blocks activation, because cotransfection of CBP-(1100-1286) reduces RasV12-driven activation of SRE and E74 luciferase reporters. Repression is relieved moderately or strongly by linking the bromodomain to the N- or C-terminal transactivation domains of CBP, respectively. These results are consistent with a model in which CBP is constitutively bound to the SRE in a higher order complex that would facilitate the rapid transcriptional activation of c-fos by signaling-driven phosphorylation.
Nissen
L J
LJ
Institut de Génétique Moléculaire de Montpellier, IFR24, CNRS, 1919 Rte. de Mende, Montpellier 34293, France.
Gelly
J C
JC
Hipskind
R A
RA
D016475:3T3 Cells; D000818:Animals; D050882:CREB-Binding Protein; D016384:Consensus Sequence; D004247:DNA / Q000378:metabolism; D018983:DNA Footprinting; D019175:DNA Methylation; D004268:DNA-Binding Proteins / Q000378:metabolism; D005656:Fungal Proteins / Q000235:genetics / Q000378:metabolism; D016762:Genes, fos; D046911:Macromolecular Substances; D051379:Mice; D008954:Models, Biological; D009687:Nuclear Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D017434:Protein Structure, Tertiary; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D020218:Response Elements; D029701:Saccharomyces cerevisiae Proteins; D026362:Serum Response Factor; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism; D015533:Transcriptional Activation; D050807:ets-Domain Protein Elk-1
D004268:DNA-Binding Proteins; C494113:Elk1 protein, mouse; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D046911:Macromolecular Substances; D009687:Nuclear Proteins; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D026362:Serum Response Factor; D015534:Trans-Activators; D014157:Transcription Factors; D050807:ets-Domain Protein Elk-1; D004247:DNA; D050882:CREB-Binding Protein; C494364:Crebbp protein, mouse