Altered pharmacology and distinct coactivator usage for estrogen receptor-dependent transcription through activating protein-1

doi:10.1073/pnas.0407113102

Altered pharmacology and distinct coactivator usage for estrogen receptor-dependent transcription through activating protein-1

^*Department of Molecular Biology and Genetics and ^‡Graduate Field of Biochemistry, Molecular and Cell Biology, Cornell University, Ithaca, NY 14853; ^¶Department of Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine, Baltimore, MD 21205; and ^∥Department of Pharmacology, Weill Medical College of Cornell University, New York, NY 10021

Edited by Ronald M. Evans, The Salk Institute for Biological Studies, La Jolla, CA (received for review September 24, 2004)

Abstract

Estrogen signaling occurs through at least two distinct molecular pathways: (i) direct binding of liganded estrogen receptors (ERs) to estrogen-responsive DNA elements (EREs) (the “ER/ERE pathway”) and (ii) indirect recruitment of liganded ERs to activating protein-1 (AP-1)-responsive DNA elements via heterodimers of Fos and Jun (the “ER/AP-1 pathway”). We have developed a biochemical assay for examining ligand-regulated transcription by ERs in the ER/AP-1 pathway. This assay recapitulates the altered (i.e., agonistic) pharmacology of selective estrogen receptor modulator drugs in this pathway reported previously by using various cell-based assays. We used our biochemical assay to examine the detailed mechanisms of ER/AP-1-dependent transcription. Our studies indicate that (i) ERα/AP-1 complexes play a critical role in promoting the formation of stable RNA polymerase II preinitiation complexes leading to transcription initiation, (ii) chromatin is a key determinant of estrogen and selective estrogen receptor modulator signaling in the ERα/AP-1 pathway, (iii) distinct domains of ERα are required for recruitment to DNA-bound Fos/Jun heterodimers and transcriptional activation at AP-1 sites, and (iv) different enhancer/activator combinations in the ERα and AP-1 pathways use coactivators in distinct ways. These studies have increased our understanding of the molecular mechanisms underlying ligand-dependent signaling in the ER/AP-1 pathway and demonstrate the usefulness of this biochemical approach.

Footnotes

↵ ** To whom correspondence should be addressed. E-mail: wlk5{at}cornell.edu.
↵ † Present address: Genome Institute of Singapore, 60 Biopolis Street, Singapore 138672.
↵ § Present address: Department of Biology, University of Puerto Rico, Arecibo, Puerto Rico 00613.
Author contributions: E.C., M.L.A., and W.L.K. designed research; E.C. and M.L.A. performed research; E.C., M.L.A., P.A.C., and W.L.K. analyzed data; and E.C., M.L.A., and W.L.K. wrote the paper.
This paper was submitted directly (Track II) to the PNAS office.
Abbreviations: ER, estrogen receptor; SERM, selective estrogen receptor modulator; AF, activation function; ERE, estrogen response element; DBD, DNA-binding domain; LBD, ligand-binding domain; RID, receptor interaction domain; PID, p300/CBP interaction domain; OHT, hydroxytamoxifen; Ral, raloxifene; AP-1, activating protein-1.