Hormone-dependent interaction between the amino- and carboxyl-terminal domains of progesterone receptor in vitro and in vivo

Mol Endocrinol. 1999 Jun;13(6):910-24. doi: 10.1210/mend.13.6.0300.


Full transcriptional activation by steroid hormone receptors requires functional synergy between two transcriptional activation domains (AF) located in the amino (AF-1) and carboxyl (AF-2) terminal regions. One possible mechanism for achieving this functional synergy is a physical intramolecular association between amino (N-) and carboxyl (C-) domains of the receptor. Human progesterone receptor (PR) is expressed in two forms that have distinct functional activities: full-length PR-B and the amino-terminally truncated PR-A. PR-B is generally a stronger activator than PR-A, whereas under certain conditions PR-A can act as a repressor in trans of other steroid receptors. We have analyzed whether separately expressed N- (PR-A and PR-B) and C-domains [hinge plus ligand-binding domain (hLBD)] of PR can functionally interact within cells by mammalian two-hybrid assay and whether this involves direct protein contact as determined in vitro with purified expressed domains of PR. A hormone agonist-dependent interaction between N-domains and the hLBD was observed functionally by mammalian two-hybrid assay and by direct protein-protein interaction assay in vitro. With both experimental approaches, N-C domain interactions were not induced by the progestin antagonist RU486. However, in the presence of the progestin agonist R5020, the N-domain of PR-B interacted more efficiently with the hLBD than the N-domain of PR-A. Coexpression of steroid receptor coactivator-1 (SRC-1) and the CREB binding protein (CBP), enhanced functional interaction between N- and C-domains by mammalian two-hybrid assay. However, addition of SRC-1 and CBP in vitro had no influence on direct interaction between purified N- and C-domains. These results suggest that the interaction between N- and C-domains of PR is direct and requires a hormone agonist-induced conformational change in the LBD that is not allowed by antagonists. Additionally, coactivators are not required for physical association between the N- and C-domains but are capable of enhancing a functionally productive interaction. In addition, the more efficient interaction of the hLBD with the N-domain of PR-B, compared with that of PR-A, suggests that distinct interactions between N- and C-terminal regions contribute to functional differences between PR-A and PR-B.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Binding Sites
  • CREB-Binding Protein
  • HeLa Cells / drug effects
  • HeLa Cells / metabolism
  • Histone Acetyltransferases
  • Hormone Antagonists / metabolism
  • Hormone Antagonists / pharmacology
  • Humans
  • Insecta / virology
  • Mammals
  • Mifepristone / metabolism
  • Mifepristone / pharmacology
  • Nuclear Proteins / metabolism*
  • Nuclear Receptor Coactivator 1
  • Peptide Fragments / genetics
  • Peptide Fragments / isolation & purification
  • Peptide Fragments / metabolism
  • Progesterone / metabolism
  • Progesterone / pharmacology
  • Progesterone Congeners / metabolism
  • Progesterone Congeners / pharmacology
  • Promegestone / metabolism
  • Promegestone / pharmacology
  • Receptors, Progesterone / drug effects
  • Receptors, Progesterone / genetics*
  • Receptors, Progesterone / metabolism*
  • Recombinant Proteins / genetics
  • Recombinant Proteins / metabolism
  • Trans-Activators / metabolism*
  • Transcription Factors / genetics
  • Transcription Factors / metabolism*


  • Hormone Antagonists
  • Nuclear Proteins
  • Peptide Fragments
  • Progesterone Congeners
  • Receptors, Progesterone
  • Recombinant Proteins
  • Trans-Activators
  • Transcription Factors
  • Mifepristone
  • Progesterone
  • Promegestone
  • CREB-Binding Protein
  • CREBBP protein, human
  • Histone Acetyltransferases
  • NCOA1 protein, human
  • Nuclear Receptor Coactivator 1