Hormonal Targeting of Nuclear Complexes to Chromatin

1. Hormonal Targeting of Nuclear Complexes to Chromatin SIGMA-ALDRICH

2. Hormonal Targeting of Nuclear Complexes to Chromatin In the absence of ligand, a silencing mediator of retinoid and thyroid hormone receptor (SMRT)-mSin3a-histone deacetylase-1 (HDAC-1) complex associates with the nuclear retinoic acid receptor (RAR)-retinoid X receptor (RXR) heterodimeric complex. The HDAC activity of the complex maintains the tight association between deacetylated histones and chromatin that results in repressed gene transcription. When 9-cis retinoic acid binds to the RAR-RXR heterodimeric complex the corepressor complex dissociates from the receptor complex with simultaneous recruitment of a coactivator comple, that includes CREB-binding protein (CBP), CBP-associated factor (p/CAF), and steroid receptor coactivator-1 (SRC-1). The receptor/coactivator complex activates histone acetyltransferase (HAT). Acetylated histone dissociates from the chromatin, allowing the preinitiation complex (PIC) to bind to DNA and the ligand heterodimeric RAR-RXR-coactivator complex to bind to specific DNA response elements (RARE) in the promoter regions of target genes to activate transcription. References Li, H., et al., Characterization of receptor interaction and transcriptional repression by the corepressor SMRT. Mol. Endocrinol., 11, 2025-2037 (1997). Blanco, J.C., et al., The histone acetylase PCAF is a nuclear receptor coactivator. Genes Dev., 12, 1638-1651 (1998). Minucci, S., et al., Retinoid receptors in health and disease: co-regulators and the chromatin connection. Semin. Cell Dev. Biol., 10, 215-225.(1999).