Review Article

PPAR in Obesity: Sex Difference and Estrogen Involvement

Figure 2

Activation and repression of nuclear receptor activity. (a) In the absence of ligand, nuclear receptors (NRs) are associated with corepressor complexes that bind Sin3 and histone deacetylase (HDAC), thereby turning off gene transcription. Some steroid receptors can recruit this complex when they are occupied by antagonists although they do not seem to be associated with corepressors in the unliganded state. (b) In the presence of ligand, NRs generally recruit coactivator complexes, PCAF histone acetyltransferase protein, general transcription factors, and RNA polymerase II to induce gene transcription. GTF: general transcription factor; RNA pol II: RNA polymerase II; PCAF: P300/CBP-associated factor.
584296.fig.002a
(a) Repression: no ligand or antagonist binding
584296.fig.002b
(b) Activation: agonist binding