The TRAP220 component of a thyroid hormone receptor- associated protein (TRAP) coactivator complex interacts directly with nuclear receptors in a ligand-dependent fashion

The TRAP220 component of a thyroid hormone receptor- associated protein (TRAP) coactivator complex interacts directly with nuclear receptors in a ligand-dependent fashion

Laboratory of Biochemistry and Molecular Biology, The Rockefeller University, New York, NY 10021

Contributed by Robert G. Roeder

Abstract

Cognate cDNAs are described for 2 of the 10 thyroid hormone receptor-associated proteins (TRAPs) that are immunopurified with thyroid hormone receptor α (TRα) from ligand-treated HeLa (α-2) cells. Both TRAP220 and TRAP100 contain LXXLL domains found in other nuclear receptor-interacting proteins and both appear to reside in a single complex with other TRAPs (in the absence of TR). However, only TRAP220 shows a direct ligand-dependent interaction with TRα, and these interactions are mediated through the C terminus of TRα and (at least in part) the LXXLL domains of TRAP220. TRAP220 also interacts with other nuclear receptors [vitamin D receptor, retinoic acid receptor α, retinoid X receptor α, peroxisome proliferation-activated receptor (PPAR) α, PPARγ and, to a lesser extent, estrogen receptor] in a ligand-dependent manner, whereas TRAP100 shows only marginal interactions with estrogen receptor, retinoid X receptor α, PPARα, and PPARγ. Consistent with these results, TRAP220 moderately stimulates human TRα-mediated transcription in transfected cells, whereas a fragment containing the LXXLL motifs acts as a dominant negative inhibitor of nuclear receptor-mediated transcription both in transfected cells (TRα) and in cell free transcription systems (TRα and vitamin D receptor). These studies indicate that TRAP220 plays a major role in anchoring other TRAPs to TRα during the function of the TRα–TRAP complex and, further, that TRAP220 (possibly along with other TRAPs) may be a global coactivator for the nuclear receptor superfamily.

Footnotes

↵ * C.-X.Y., M.I., and J.D.F. contributed equally to this work.
↵ † Present address: Department of Physiology, University of Maryland, School of Medicine, 660 West Redwood Street, Baltimore, MD 21201.
↵ ‡ To whom reprint requests should be addressed. e-mail: roeder{at}rockvax.rockefeller.edu.
Data deposition: The sequences reported in this paper have been deposited in the GenBank database [accession nos. AF055994 (TRAP220) and AF055995 (TRAP100)].
ABBREVIATIONS:

ERα,

estrogen receptor α;

GST,

glutathione S-transferase;

PPAR,

peroxisome proliferation-activated receptor;

RARα,

retinoic acid receptor α;

RXRα,

retinoid X receptor α;

TRAP,

thyroid hormone receptor-associated protein;

TRα,

thyroid hormone receptor α;

hTRα,

human TRα;

VDR,

vitamin D receptor