Abstract

Ras/Mitogen-Activated Protein Kinase Signaling Activates Ets-1 and Ets-2 by CBP/p300 Recruitment † Charles E. Foulds , Mary L. Nelson , Adam G. Blaszczak and Barbara J. Graves * Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, Salt Lake City, Utah ABSTRACT Cell signaling affects gene expression by regulating the activity of transcription factors. Here, we report that mitogen-activated protein kinase (MAPK) phosphorylation of Ets-1 and Ets-2, at a conserved site N terminal to their Pointed (PNT) domains, resulted in enhanced transactivation by preferential recruitment of the coactivators CREB binding protein (CBP) and p300. We discovered this phosphorylation-augmented interaction in an unbiased affinity chromatography screen of HeLa nuclear extracts by using either mock-treated or ERK2-phosphorylated ETS proteins as ligands. Binding between purified proteins demonstrated a direct interaction. Both the phosphoacceptor site, which lies in an unstructured region, and the PNT domain were required for the interaction. Minimal regions that were competent for induced CBP/p300 binding in vitro also supported MAPK-enhanced transcription in vivo. CBP coexpression potentiated MEK1-stimulated Ets-2 transactivation of promoters with Ras-responsive elements. Furthermore, CBP and Ets-2 interacted in a phosphorylation-enhanced manner in vivo. This study describes a distinctive interface for a transcription factor-coactivator complex and demonstrates a functional role for inducible CBP/p300 binding. In addition, our findings decipher the mechanistic link between Ras/MAPK signaling and two specific transcription factors that are relevant to both normal development and tumorigenesis.