Corepressor Action

Abstract

The activity of nuclear receptors such as the peroxisome proliferator-activated receptor-α (PPAR-α), which regulates the expression of genes that modulate fatty acid metabolism, can be regulated through interaction with coactivator and corepressor molecules. Understanding the nature of these interactions may help the development of drugs that effectively control lipid levels. By examining the crystal structure of a ternary complex comprised of the PPAR-α ligand-binding domain, an antagonist molecule, and the receptor-binding motif of the corepressor SMRT, Xu et al. report that a groove in the nuclear receptor contains overlapping binding sites for both coactivators and corepressors. However, in the presence of an antagonist molecule, a specific helix in the receptor is blocked from assuming an active conformation. This block results in a large domain that can specifically accommodate the receptor binding motif of a coprepressor. This mechanism may be utilized by nuclear receptors in general because the corepressor binding sequence is highly conserved.H. E. Xu, T. B. Stnaley, V. G. Montana, M. H. Lambert, B. G. Shearer, J. E. Cobb, D. D. McKee, C. M. Galardi, K. D. Plunket, R. T. Nolte, D. J. Parks, J. T. Moore, S. A. Kliewer, T. M.Willson, J. B. Stimmel, Structural basis for antagonist-mediated recruitment of nuclear co-repressors by PPARα. Nature 415, 813-817 (2002). [Online Journal]