Induction-independent recruitment of CREB-binding protein to the c-fos serum response element through interactions between the bromodomain and Elk-1

Nissen, L. J.; Gelly, J. C.; Hipskind, R. A.

J Biol Chem

2001-02-16 / vol 276 / pages 5213-21


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.

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Animals; Mice; DNA Methylation; Models, Biological; Response Elements; Protein Structure, Tertiary; Transcription Factors/genetics/metabolism; Recombinant Fusion Proteins/metabolism; Proto-Oncogene Proteins/*metabolism; DNA/metabolism; DNA-Binding Proteins/metabolism; *Genes, fos; *Saccharomyces cerevisiae Proteins; Trans-Activation (Genetics); 3T3 Cells; ets-Domain Protein Elk-1; Consensus Sequence; Macromolecular Substances; Serum Response Factor; DNA Footprinting; CREB-Binding Protein; Fungal Proteins/genetics/metabolism; Nuclear Proteins/*chemistry/genetics/*metabolism; Trans-Activators/*chemistry/genetics/*metabolism

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