The nuclear receptor coactivator PGC-1alpha exhibits modes of interaction with the estrogen receptor distinct from those of SRC-1

J Mol Biol. 2005 Apr 15;347(5):921-34. doi: 10.1016/j.jmb.2005.01.048.


Estrogen receptor (ER) function is mediated by multi-domain co-regulator proteins. A fluorescently labelled fragment of the human PGC-1alpha co-regulator (residues 91-408) bearing the two motifs most strongly implicated in interactions with nuclear receptors (NR box2 and NR box3), was used to characterize in vitro binding of PGC-1alpha to ER. Anisotropy measurements revealed that the affinity of this PGC-1alpha fragment for human ERalpha and beta was fairly strong in the presence of estradiol (approximately 5 nM), and that unlike a similar fragment of SRC-1 (570-780), PGC-191-408 exhibited ligand-independent interactions with ER, particularly with ERbeta (Kd approximately 30 nM). Competition experiments of the complex between ERalpha and fluorescently labelled PGC-1 91-408 with unlabelled SRC-1 570-780 showed that PGC-1 91-408 was an efficient competitor of SRC-1 570-780, while the inverse was not true, underscoring their distinct modes of binding. The anisotropy data provide strong evidence for a ternary complex between ERalpha, SRC-1 570-780 and PGC-1 91-408. GST-pull-down experiments with deletion mutants of ERalpha revealed that the constitutive binding of PGC-1 91-408 requires the presence of the linker domain between the DNA binding and ligand binding domains (DBD and LBD). Homology modeling studies of the different regions of full length PGC-1alpha confirmed the lack of compact tertiary structure of the N-terminal region bearing the NR box motifs, and suggested a slightly different mode of interaction compared to the NR box motifs of SRC-1. They also provided reasonable structural models for the coiled-coil dimerization motif at residues 633-675, as well as the C-terminal putative RNA binding domain, raising important questions concerning the stoichiometry of its complex with the nuclear receptors.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Anisotropy
  • Dimerization
  • Estrogen Receptor alpha / genetics
  • Estrogen Receptor alpha / metabolism*
  • Estrogen Receptor beta / genetics
  • Estrogen Receptor beta / metabolism*
  • Heat-Shock Proteins / chemistry*
  • Heat-Shock Proteins / genetics
  • Heat-Shock Proteins / metabolism*
  • Histone Acetyltransferases
  • Humans
  • Ligands
  • Models, Biological
  • Models, Molecular
  • Mutation / genetics
  • Nuclear Receptor Coactivator 1
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Protein Binding
  • Protein Structure, Tertiary
  • Spectrometry, Fluorescence
  • Thermodynamics
  • Titrimetry
  • Transcription Factors / chemistry*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*
  • Transcription, Genetic / genetics


  • Estrogen Receptor alpha
  • Estrogen Receptor beta
  • Heat-Shock Proteins
  • Ligands
  • PPARGC1A protein, human
  • Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha
  • Transcription Factors
  • Histone Acetyltransferases
  • NCOA1 protein, human
  • Nuclear Receptor Coactivator 1