Iqy

y Steroid receptor y Steroid receptor

FIGURE 13-20 Schematic models illustrating how steroid antagonists (antihormones) might block the formation of a competent ligand-receptor-mediated transcription complex. (A) In this model, a pure antagonist interferes with the nuclear-cytoplasmic shuttling process, with the result that the receptor accumulates in the cytoplasm and is degraded. Abbreviations: HRE, hormone response element; hsp 90, heat shock protein 90; AH, antihormone. (B) In this model, the key point is that an antihormone (AH) does not induce a receptor conformational change that removes a surface repressor (R) function. Abbreviations: H, hormone; AH, antihormone; AF, activation function; R, repressor function; DNA, DNA-binding domain; "w- dimerization domain; N, amino terminus. Modified with permission from Tsai, M.-J., and O'Malley, B. W. (1994). Molecular mechanisms of actions of steroid/thyroid receptor superfamily members. Ann. Rev. Biochem. 63, 451-486.

Stimulated transcription

Blocked transcription

FIGURE 13-20 Schematic models illustrating how steroid antagonists (antihormones) might block the formation of a competent ligand-receptor-mediated transcription complex. (A) In this model, a pure antagonist interferes with the nuclear-cytoplasmic shuttling process, with the result that the receptor accumulates in the cytoplasm and is degraded. Abbreviations: HRE, hormone response element; hsp 90, heat shock protein 90; AH, antihormone. (B) In this model, the key point is that an antihormone (AH) does not induce a receptor conformational change that removes a surface repressor (R) function. Abbreviations: H, hormone; AH, antihormone; AF, activation function; R, repressor function; DNA, DNA-binding domain; "w- dimerization domain; N, amino terminus. Modified with permission from Tsai, M.-J., and O'Malley, B. W. (1994). Molecular mechanisms of actions of steroid/thyroid receptor superfamily members. Ann. Rev. Biochem. 63, 451-486.

TABLE 13-9 Relative Effectiveness of Various Contraceptive Methods

Contraceptive method

Number1" (millions)

Failures/100 Women Years"

Vasectomy of the male

0 0

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