Purification and identification of p68 RNA helicase acting as a transcriptional coactivator specific for the activation function 1 of human estrogen receptor alpha.
Fiche publication
Date publication
août 1999
Journal
Molecular and cellular biology
Auteurs
Membres identifiés du Cancéropôle Est :
Dr METZGER Daniel
Tous les auteurs :
Endoh H, Maruyama K, Masuhiro Y, Kobayashi Y, Goto M, Tai H, Yanagisawa J, Metzger D, Hashimoto S, Kato S
Lien Pubmed
Résumé
The estrogen receptor (ER) regulates the expression of target genes in a ligand-dependent manner. The ligand-dependent activation function AF-2 of the ER is located in the ligand binding domain (LBD), while the N-terminal A/B domain (AF-1) functions in a ligand-independent manner when isolated from the LBD. AF-1 and AF-2 exhibit cell type and promoter context specificity. Furthermore, the AF-1 activity of the human ERalpha (hERalpha) is enhanced through phosphorylation of the Ser(118) residue by mitogen-activated protein kinase (MAPK). From MCF-7 cells, we purified and cloned a 68-kDa protein (p68) which interacted with the A/B domain but not with the LBD of hERalpha. Phosphorylation of hERalpha Ser(118) potentiated the interaction with p68. We demonstrate that p68 enhanced the activity of AF-1 but not AF-2 and the estrogen-induced as well as the anti-estrogen-induced transcriptional activity of the full-length ERalpha in a cell-type-specific manner. However, it did not potentiate AF-1 or AF-2 of ERbeta, androgen receptor, retinoic acid receptor alpha, or mineralocorticoid receptor. We also show that the RNA helicase activity previously ascribed to p68 is dispensable for the ERalpha AF-1 coactivator activity and that p68 binds to CBP in vitro. Furthermore, the interaction region for p68 in the ERalpha A/B domain was essential for the full activity of hERalpha AF-1. Taken together, these findings show that p68 acts as a coactivator specific for the ERalpha AF-1 and strongly suggest that the interaction between p68 and the hERalpha A/B domain is regulated by MAPK-induced phosphorylation of Ser(118).
Mots clés
Adenocarcinoma, pathology, Amino Acid Sequence, Animals, Breast Neoplasms, pathology, Calcium-Calmodulin-Dependent Protein Kinases, physiology, DEAD-box RNA Helicases, Estrogen Receptor alpha, Female, Gene Expression Regulation, Humans, Molecular Sequence Data, Neoplasm Proteins, isolation & purification, Phosphorylation, Protein Binding, Protein Kinases, Protein Processing, Post-Translational, Protein Structure, Tertiary, RNA Helicases, isolation & purification, Rabbits, Receptors, Estrogen, chemistry, Recombinant Fusion Proteins, physiology, Sequence Analysis, Transcription, Genetic, Tumor Cells, Cultured
Référence
Mol. Cell. Biol.. 1999 Aug;19(8):5363-72