%0 Journal Article
%T C/EBPBeta and Elk-1 synergistically transactivate the c-fos serum response element
%A Mary Hanlon
%A Linda M Bundy
%A Linda Sealy
%J BMC Cell Biology
%D 2000
%I BioMed Central
%R 10.1186/1471-2121-1-2
%X In this report, we demonstrate that Elk-1 and C/EBP¦Â functionally synergize in transactivation of both a Gal4 reporter plasmid in concert with Gal4-SRF and in transactivation of the SRE. Interestingly, this synergy is only observed upon activation of Ras-dependent signaling pathways. Furthermore, we show that Elk-1 and C/EBP¦Â could interact both in an in vitro GST-pulldown assay and in an in vivo co-immunoprecipitation assay. The in vivo interaction between the two proteins is dependent on the presence of activated Ras. We have also shown that the C-terminal domain of C/EBP¦Â and the N-terminal domain of Elk-1 are necessary for the proteins to interact.These data show that C/EBP¦Â and Elk-1 synergize in SRF dependent transcription of both a Gal-4 reporter and the SRE. This suggests that SRF, TCF, and C/EBP¦Â are all necessary for maximal induction of the c-fos SRE in response to mitogenic signaling by Ras.c-fos is a member of the family of immediate early genes, and its transcription is transiently induced in response to mitogenic signals [1]. The serum response element (SRE) is located approximately 300 bp upstream of the transcriptional start site in the c-fos promoter and is necessary for serum induction of c-fos [2]. The SRE binds a transcription factor named serum response factor (SRF) which was found to be necessary, but not sufficient, for serum induction of the SRE [3,4,5]. In vivo footprinting analysis shows that SRF is constitutively bound to the SRE in both quiescent and growth factor stimulated cells [6]. This suggests that it is the transcriptional activation of a complex of SRF and its accessory proteins that is regulated rather than regulation of SRF DNA binding.The ternary complex factors (TCFs) are members of the ets family of transcription factors. The TCF family members Elk-1 [7], SAP-1 [8], and SAP-2/ERP/NET [9, 10] have been found to have a role in regulating the SRE. TCFs cannot bind the SRE autonomously, but require protein-protein interactions w
%U http://www.biomedcentral.com/1471-2121/1/2