Characterization of transactivational property and coactivator mediation of rat mineralocorticoid receptor activation function-1 (AF-1).
The autonomous activation function-2 (AF-2) in the mineralocorticoid receptor (MR) E/F domain is known to play a major role in the ligand-induced transactivation function of MR; however, it remained unclear about the transactivation function of its A/B domain. We therefore tried to characterize the MR A/B domain as the AF-1 and further studied the actions of known coactivators for AF-2 in the E/F ligand-binding domain in the function of the MR A/B domain. Deletion analyses of rat and human MRs revealed that the A/B domains harbor a transactivation function acting as AF-1. The MR mutant (E959Q) with a point mutation in helix 12, which causes a complete loss of MR AF-2 activity, still retained ligand-induced transactivation function, indicating a significant role for AF-1 in the full activity of the ligand-induced MR function. Among the coactivators tested to potentiate the MR AF-2, TIF2 and p300 potentiated the MR AF-1 through two different core regions [amino acids (a.a.) 1-169, a.a. 451-603] and exhibited functional interactions with the MR A/B domain in the cultured cells. However, such interactions were undetectable in a yeast and in an in vitro glutathione-S-transferase pull-down assay, indicating that the functional interaction of TIF2 and p300 with the MR A/B domain to support the MR AF-1 activity require some unknown nuclear factor(s) or a proper modification of the A/B domain in the cells.
Fuse
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Pharmacological Research Department, Teikoku Hormone Manufacturing Company, Ltd., Tokyo, Japan.
Kitagawa
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Kato
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D000818:Animals; D015153:Blotting, Western; D019556:COS Cells; D050881:E1A-Associated p300 Protein; D004926:Escherichia coli / Q000235:genetics; D017353:Gene Deletion; D005822:Genetic Vectors; D005982:Glutathione Transferase / Q000235:genetics; D006801:Humans; D009687:Nuclear Proteins / Q000378:metabolism / Q000494:pharmacology; D051958:Nuclear Receptor Coactivator 2; D017354:Point Mutation; D051381:Rats; D018161:Receptors, Mineralocorticoid / Q000737:chemistry / Q000235:genetics / Q000502:physiology*; D011993:Recombinant Fusion Proteins; D012441:Saccharomyces cerevisiae / Q000235:genetics; D013329:Structure-Activity Relationship; D015534:Trans-Activators / Q000378:metabolism / Q000494:pharmacology; D014157:Transcription Factors / Q000378:metabolism / Q000494:pharmacology; D015533:Transcriptional Activation; D014162:Transfection
C498001:NCOA2 protein, human; C498003:Ncoa2 protein, rat; D009687:Nuclear Proteins; D051958:Nuclear Receptor Coactivator 2; D018161:Receptors, Mineralocorticoid; D011993:Recombinant Fusion Proteins; D015534:Trans-Activators; D014157:Transcription Factors; D050881:E1A-Associated p300 Protein; C494362:Ep300 protein, rat; D005982:Glutathione Transferase