STRUCTURAL STUDIES OF MUTANT GLUCOCORTICOID RECEPTOR TRANSACTIVATION DOMAINS ESTABLISH A LINK BETWEEN TRANSACTIVATION ACTIVITY IN-VIVO AND ALPHA-HELIX-FORMING POTENTIAL IN-VITRO

We have previously shown, using circular dichroism spectroscopy, that the tau l core peptide has alpha-helix-forming potential in vitro [Dah lman-Wright et al. (1995) Proc. Natl. Acad Sci. U.S.A. 92; 1699-1703]. The tau l core peptide is a 58-amino acid peptide, constituting the c ore of the transactivation activity of the tau l major transactivation domain of the human glucocorticoid receptor [Dahlman-Wright et al. (1 994) Proc. Natl. Acad. Sci. U.S.A. 91, 1619-1623]. Further structural studies of the peptide, using NMR spectroscopy, identified three segme nts with alpha-helical character. In this report we show that reduced protein expression or stability is not responsible for the reduced in vivo transactivation potential of tau l core peptides with proline sub stitutions in proposed alpha-helical regions. Rather, the reduced alph a-helix propensity of the corresponding purified peptides in vitro sug gests that alpha-helices are involved in the molecular mechanism of gl ucocorticoid receptor mediated changes in gene activity.