Retinoic acid receptor alpha–Silencing mediator for retinoid and thyroid hormone receptors corepressor complex (RARα–SMRT complex)

The RARα–SMRT corepressor complex is a multi-protein assembly that plays a pivotal role in the transcriptional regulation of genes involved in cell growth and differentiation (UniProt P10276, Q9Y6Q8). RARα (Retinoic Acid Receptor alpha) is a nuclear receptor that, in its unliganded state, recruits the SMRT (Silencing Mediator for Retinoid and Thyroid hormone receptors) corepressor to specific DNA sequences known as retinoic acid response elements (RAREs) (PMID: 9428512). This recruitment leads to the assembly of a repressive complex containing histone deacetylases (HDACs), which maintain chromatin in a condensed, transcriptionally inactive state. In diseases such as Acute Promyelocytic Leukemia (APL), the formation of the PML-RARα fusion protein results in a complex that binds SMRT with abnormally high affinity, constitutively repressing genes essential for myeloid maturation (PMID: 10675330). Therapeutic intervention with pharmacological doses of all-trans retinoic acid (ATRA) promotes the dissociation of SMRT from the receptor, facilitating the recruitment of coactivators and the subsequent induction of terminal differentiation in leukemic blasts (NIH/NCI).

Other names

RARα-NCOR2 complexRetinoic acid receptor alpha-SMRT complexRAR-alpha/SMRT corepressor complexPML-RARα/SMRT complex

Drugs like all-trans retinoic acid (ATRA) bind to the RARα component of the complex, inducing a conformational change that leads to the dissociation of the SMRT corepressor and the subsequent recruitment of coactivators (e.g., p300/CBP), thereby switching the complex from a transcriptional repressor to an activator (PMID: 9428512, 10675330).