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Metabolic Research Unit University of California School of Medicine San Francisco California 94143-0540
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ABSTRACT |
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 TOP ABSTRACT INTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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INTRODUCTION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Thyroid hormone-dependent enhancement of basal promoter activity involves recruitment of two types of coactivator proteins. The TRs bind to a closely related family of p160 coactivators, including GRIP1 (TIF2/NCoA-2), SRC-1 (NCoA-1), and ACTR (pCIP/Rac3/AIB1/TRAM-1) (8, 9, 10, 11). The p160s, in turn, bind to other coactivators, including the integrator molecule CBP/p300 and p/CAF, both of which possess histone acetyltransferase activity. The TRs also bind TRAP220 (12), a component of the TRAP (DRIP/ARC/SMCC) complex that potentiates TR-dependent transcription from naked DNA templates in vitro, but also regulates transcription from DNA templates that have been assembled into chromatin in vitro (13, 14, 15, 16, 17). Thus, liganded TRs activate transcription by recruiting large coactivator complexes, which work by either modifying chromatin or via unspecified effects upon general initiation factors. In contrast, unliganded TRs repress transcription by recruiting corepressor proteins, which are released upon hormone binding. The TRs bind to nuclear receptor corepressor (N-CoR) (RIP-13) and to the closely related protein SMRT (TRAC-2) (18, 19, 20, 21, 22, 23, 24). Both N-CoR and SMRT, in turn, bind a large complex that contains mSin3a, SAP30, c-ski, and histone deace-tylases (HDACs) (25, 26, 27) and also bind directly to class II HDACs (28, 29). Thus, unliganded TRs repress transcription by recruiting large corepressor complexes, which work, at least in part (30), by deacetylating histones.
Recent studies have focused on the structural basis of coactivator and
corepressor recruitment. Like most nuclear receptors, TRs possess a
strong ligand- dependent transactivation function (AF-2) that is
located within the receptor ligand-binding domain (LBD) and serves as a
docking site for p160 coactivators (31, 32). A combination of x-ray
crystallography and site- directed mutagenesis has revealed that
the residues that comprise AF-2 form a small hydrophobic cleft upon the
surface of the T3-liganded TR-LBD (32, 33).
Mutational analysis of the p160s and crystallographic analysis of
nuclear receptor/p160 cocrystals revealed that AF-2 binds to short,
conserved 
-helical motifs (termed NR boxes, consensus LXXLL)
(34, 35, 36, 37, 38, 39, 40, 41). Initial structure-function analysis of the TRs and retinoic
acid receptors suggested that key residues for corepressor binding were
located near the junction of the hinge and LBD (18). However, the
TR-LBD crystal structure revealed that these residues were not on the
surface of the molecule (33), suggesting that mutations of these
residues affect corepressor binding indirectly. Other evidence
indicated that coactivators and corepressors were in dynamic
equilibrium on the nuclear receptor (8, 11, 42) and that key residues
for transcriptional repression by v-erbA, an oncogenic viral homolog of
TR, and for transcriptional repression and corepressor binding by the
orphan receptors Rev-erbA and RVR, actually resided within the AF-2
hydrophobic cleft (43, 44). This suggested that similar mechanisms
might underlie both coactivator and corepressor recruitment and
prompted us to search the N-CoR primary sequence for motifs that bear
similarities to nuclear receptor boxes. We find, in agreement with
recently published studies of others (45, 46, 47), that the N-CoR C
terminus contains a repeated receptor interaction domain (ID) that
contains the conserved hydrophobic core motif I/LXXII. More
surprisingly, we find that N-CoR actually contains three of these IDs,
rather than the previously reported two. We present several lines of
evidence that the hitherto unrecognized motif (ID3) is a fully
functional TR binding site and that the three IDs represent the
totality of TR binding activity. We also show that the IDs are
comprised of both a hydrophobic core and distinct adjacent sequences
and that a hybrid peptide containing distinct adjacent sequences from
ID3 and ID1 binds more tightly to TR.
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RESULTS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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). The C-terminal binding
region contained a single short hydrophobic motif that resembled the NR
box (LEDII, amino acids 2,276–2,281). The N-terminal binding region
contained two of these motifs (ICQII, amino acids 2,073–2,077; IDVII,
amino acids 1,949–1,953). We refer to these motifs as ID1, ID2, and
ID3 (from C-terminal to N-terminal). During the course of this study,
ID1 and ID2 were also identified by other groups (45, 46, 47) but ID3 was
not.
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). The
strongest conservation between N-CoR and SMRT ID1 was C-terminal to the
core motif, whereas the strongest conservation between N-CoR and SMRT
ID2 was N terminal to the core motif. While N-CoR ID3 did not have an
obvious counterpart within SMRT, it did resemble N-CoR ID2. In
particular, ID3 and ID2 contained an IXXII core, a conserved Arg and
the sequence ITØA N-terminal to the cores, and a conserved Thr
immediately C terminal to the core. Because of these homologies, we
elected to examine all three IDs as candidate TR binding sites.
The ID Motifs Mediate TRß/N-CoR Interactions
To test whether each of the three IDs represented a functional TR
binding site, we synthesized short peptides that spanned the entire
region of conservation between N-CoR and SMRT ID1 or N-CoR ID3 and
N-CoR and SMRT ID2 (Fig. 2A). We then
asked whether these short ID peptides would compete for TRß/N-CoR
interactions in vitro (Fig. 2B). ID1 and ID3 showed
half-maximal competition at 0.3–1 µg of peptide. ID2 was weaker,
with half-maximal competition requiring 1–3 µg of peptide. Overall,
the efficiency of ID peptide competition for TRß/N-CoR interactions
was comparable to the efficiency of NR box peptide competition for
TRß/GRIP1 interactions (37). Moreover, several mutant peptides, some
of which conserved overall ID hydrophobicity, failed to compete for
TR/N-CoR interactions (data not shown and see Figs. 6 and 7). Thus,
each of the three ID motifs could represent a functional TR binding
site.
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shows that, in agreement with
previous results (22, 24, 45, 46, 47), N-CoR fragments overlapping isolated
ID1 or ID2 bound the TR in the absence of ligand. A N-CoR fragment that
overlapped the ID3 IXXII motif (amino acids 1,944–2,031) also showed
significant binding to TR. TR binding to ID3 was robust, even though
this N-CoR fragment lacks some of the conserved ID3 sequences that lie
to the N terminus of amino acid 1,944. Thus, the N-CoR C terminus
contains three distinct TR binding regions, each of which overlaps an
ID motif.
To determine whether the ID motifs themselves were required for
N-CoR/TRß interactions in vitro, we prepared a vector that
expresses the N-CoR C terminus (amino acids 1,681–2,453) and
introduced mutations into the hydrophobic core of each ID. Figure 3 shows that the N-CoR C-terminal
fragment (WT) bound strongly to TRß in the absence of ligand, and
that binding was reduced by T3. Similar N-CoR
fragments that retained either ID3+ID2 or ID3+ID1 showed small
reductions in TRß binding in the absence of ligand, but an N-CoR
fragment that retained only ID2+ID1 showed a larger reduction in TRß
binding. Phosphoimaging of several experiments revealed that ID3+ID2
allowed more than 90% of the level of wild type N-CoR binding to
TRß, ID3+ID1 allowed up to 70%, and that ID2+ID1 allowed 40–60%.
Thus, significant N-CoR binding is obtained with any two IDs, but the
combination of ID3+ID2 is preferred and the combination of ID2+ID1 is
weakest. By contrast, single IDs were insufficient to allow significant
binding to TRß. An N-CoR fragment that only contained ID3 did give
some weak binding to TRß (
5% of wild type), but fragments that
contained only ID2 or ID1, or no IDs failed to bind TRß. Taken
together, these results point toward several conclusions. First, the
N-CoR IDs are essential for TR binding. Second, because the N-CoR
triple mutant failed to bind to TRß, there is no additional TR
binding site within the N-CoR C terminus. Third, because each possible
ID pair allows significant TRß binding, yet isolated IDs do not, the
IDs must cooperate in TRß binding. Lastly, and most surprisingly,
because mutation of ID3 leads to the largest reduction in TRß
binding, and because isolated ID3, but not ID1 or ID2, is sufficient
for weak residual binding to the TRß-LBD, ID3 may be the strongest of
the three IDs for TRß binding in vitro.
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shows that, as expected, Gal-TR
repressed transcription in CEF cells by 3-fold in the absence of
T3 (left panel) and enhanced
transcription by 15-fold in the presence of T3
(right panel). The N-CoR C-terminus (WT) reversed the
repression (left panel), but not the ligand-dependent
activation (right panel). Thus, consistent with previous
observations (24), the N-CoR C terminus interferes with the ability of
unliganded TRß-LBD to repress transcription.
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Next, we examined TRß binding to the IDs in two-hybrid assays in CEF
cells (Fig. 5A). A N-CoR fragment that
contained all three IDs (ID3, -2, and -1) recruited unliganded
TRß-VP16, but not liganded TRß-VP16. By contrast, a similar
construction in which all three ID motifs were mutated (mID3, -2, and
-1) failed to recruit TRß-VP16, even when TRß-VP16 was
overexpressed (not shown). Thus, the three IDs constitute all of the TR
IDs within the N-CoR C terminus in vivo. In parallel, N-CoR
fragments that contained isolated ID3 or isolated ID1 both recruited
TRß-VP16, but their mutated equivalents did not. An N-CoR
fragment that contained ID2 only showed weak interactions with
TRß-VP16. However, the relative weakness of this interaction was
overcome when TRß-VP16 was overexpressed (Fig. 5B). Thus, each ID
binds TRß-VP16 in vivo, but ID3 and ID1 are strongest.
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, inset). This indicates that TRß/ID1 interactions possess
both ligand-dependent and ligand-independent components. Despite these
subtleties, our results suggest that all three IDs bind TRß in
vivo, and that the binding of each ID motif to TRß
recapitulates the pattern of N-CoR binding to TRß.
The IDs Are Composed of a Hydrophobic Core (I/LXXII) Along with
Distinct Adjacent Sequences
While we originally identified the IDs on the basis of their
resemblance to the coactivator NR box (LXXLL), it is clear that some
mechanism allows N-CoR to bind preferentially to unliganded TRs and
coactivators to bind preferentially to liganded TRs. We asked whether
the different types of hydrophobic residues within the N-CoR motifs
(Ile, I/LXXII) and the NR box motifs (Leu, LXXLL) were sufficient to
account for this preference. We synthesized a mutant N-CoR ID1 peptide
(ID1-LL), in which key Ile residues were substituted with Leu, so that
it resembled a p160 NR box, and a mutant GRIP1 NR box2 peptide in which
key Leu residues were substituted with Iles, so that it resembled an
N-CoR ID motif (Fig. 6A).
Figure 6B confirms the observations, shown above, that the N-CoR ID1
peptide competed for the binding of unliganded TRß to N-CoR
(left panel) and also shows that Box2, ID1-LL, and Box2-II
did not. In parallel (right panel), the ID1 peptide failed
to compete for the binding of T3-liganded TRß
to GRIP1, but Box2 competed efficiently. Both ID1-LL and Box2-II did
not. Thus, even Ile/Leu exchanges, which conserve the hydrophobicity of
the peptides, abolished their respective abilities to compete for
TRß/N-CoR and TRß/GRIP1 interactions. Moreover, the Ile/Leu
exchanges failed to allow the N-CoR ID peptide to compete for
TRß/GRIP1 interactions or the GRIP1 NR box peptide to compete for
TRß/N-CoR interactions. This indicates that the binding preferences
of N-CoR for unliganded TRß, and GRIP1 for liganded TRß, are not
dictated solely by the identity of the conserved hydrophobic residues
within their TRß binding motifs.
We next examined the sequence requirements for ID motif/TRß
interaction. In the case of ID3, Ala substitutions within the core
hydrophobic Ile residues (m1) abolished its ability to compete for
TRß/N-CoR interactions (Fig. 7A).
Likewise, Ala substitutions at different locations within the conserved
ID3 N-terminal region either completely abolished (m2, m3, m5), or
partially reduced (m4), the ability of ID3 to compete for TRß/N-CoR
interactions. In the case of ID1, Ala substitutions within the Leu and
Ile residues of the ID1 core, and a Leu residue within the conserved
region of the ID1 C terminus, were sufficient to abolish competition,
whether they were placed within the same peptide (m1), or within
different peptides (m2–m4) (Fig. 7B). Substitution of the Glu residue
within the ID1 core, which is conserved between N-CoR and SMRT, also
abolished competition (m5), but substitution of Asp, which is not
conserved, did not (m6). Thus, residues both within and outside of the
hydrophobic core motifs are required for ID3 and ID1 peptides to
compete for TRß/N-CoR interactions.
Finally, because the area of best conservation between N-CoR ID3 and
N-CoR and SMRT ID2 lay N-terminal to the core motif and the area of
best conservation between N-CoR and SMRT ID1 lay C terminal to the core
motif, we prepared an ID3/ID1 hybrid peptide that contained both
regions (Fig. 7C). Half-maximal competition was obtained with as little
as 10–30 ng of hybrid peptide and complete competition was obtained
with as little as 300 ng to 1 µg of peptide. In parallel,
half-maximal competition for TRß/N-CoR interactions required 0.3–1
µg of the ID3 or ID1 peptides (see Fig. 2). Thus, the hybrid peptide
competes for TRß binding to N-CoR more efficiently than the parental
peptides, suggesting that the binding of the IDs to TRß is suboptimal
and that the identity and position of the TR binding determinants
outside the core motif differs between the IDs.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Our data also indicate that isolated ID3 and ID1 are stronger than
isolated ID2 and that any combination of two IDs is sufficient for
strong TR binding, although the particular combination of ID3 and ID2
is preferred both in vitro (Fig. 3) and in vivo
(Fig. 4). Nonetheless, there are some apparent discrepancies between
assays that need to be resolved. For example, any pair of IDs was
capable of binding TR in vitro, and isolated ID3 was
sufficient for residual interactions with the TR (Fig. 3). However, the
specific combination of ID2 and ID3 was required for N-CoR dominant
negative activity in vivo, and other pairs of IDs or single
IDs were not functional (Fig. 4). Furthermore, a GST-N-CoR fragment
that only contains ID2 binds strongly to TR (Fig. 2C), even though
isolated ID2 appeared to bind relatively weakly to TR in other assays.
We suggest that these apparent discrepancies arise from differences in
the sensitivity and linear range of different assays. Thus,
glutathione-S-transferase (GST)-pull-down assays would
detect relatively weak TR/N-CoR interactions, whereas the dominant
negative interference assay would only detect strong TR/N-CoR
interactions. In accordance with the notion that it is important to
"tune" each assay for true quantitative comparisons, it was
possible to detect differences between the IDs in mammalian two-hybrid
assays in the presence of low levels of TR (Fig. 5A), but these
differences disappeared when the TR was overexpressed (Fig. 5B).
Our studies also raise the question of whether N-CoR might contain yet more unrecognized IDs. We found that mutation of all three IDs completely abolishes the ability of full length N-CoR to bind to the TRß-LBD (not shown), suggesting that N-CoR lacks any unidentified strong TRß-LBD binding site. Thus, we presently favor the idea that N-CoR only contains three IDs. While we have not directly examined TR interactions with SMRT in this study, sequence comparisons failed to reveal an ID3 motif at a conserved position, or any other position, in the SMRT primary sequence, nor any obvious homologies between other surrounding ID3 residues and SMRT. We therefore suggest that SMRT only contains two IDs. We stress that this conclusion is based only on sequence comparisons and needs to be treated with caution. Strong interactions between SMRT and TR can be observed even in the absence of ID1 (46). While this binding may simply reflect the interactions of SMRT ID2 with TR, it is also possible that SMRT contains both an ID2 and additional sequences that bind to TR, and that these sequences are not recognizable from the sequence data alone.
The IDs Cooperate in TR Binding
Our studies indicate that the IDs cooperate in TR binding, both
in vitro and in vivo, just as the p160 NR boxes
cooperate in nuclear receptor binding (37). This cooperativity provides
obvious advantages for the sensitivity of hormone response: binding of
ligand to either receptor molecule within a homo- or heterodimer pair
would result in complete corepressor release. The reasons why N-CoR
would contain three distinct ID motifs, when two are sufficient for
high-affinity TRß interactions, are less clear. TRß shows some
preference for the pairing of ID3+ID2 (Figs. 3, 4, and 5), even though
ID2 is relatively weak when examined in isolation (Figs. 3 and 5).
Other nuclear receptors show a preference for ID1 (45, 46, 47). This
finding is reminiscent of the preference of different nuclear receptors
for different p160 NR boxes (34, 35, 36, 37, 38, 39). Thus, one possible explanation
for the presence of three IDs in the N-CoR C terminus is that they
might allow for higher order interactions between separate nuclear
receptors, e.g. a dimer and a monomer might be able to bind
simultaneously to a single N-CoR molecule.
The IDs Are Composed of a Hydrophobic Core and Distinct Adjacent
Sequences: Speculations on the Nature of the TR/N-CoR Interface
The same nuclear receptor hydrophobic cleft that mediates
interactions with p160 coactivators also mediates interactions with
corepressors (43, 44, 45, 46, 47, 49). Moreover, N-CoR and SMRT ID motifs contain
the core consensus sequence I/LXXI/VI, which resembles the NR box
consensus LXXLL. Despite these similarities, there must be some
mechanism that allows only unliganded TRß to bind N-CoR and only
liganded TRß to bind GRIP1. This preference cannot be accounted for
by the nature of hydrophobic residues within the ID motif and NR box
core motifs (Fig. 6). N-CoR and GRIP1 must therefore recognize distinct
structural features of TRß that are regulated by ligand.
What are the mechanisms that N-CoR uses to recognize unliganded TR? Our
results, and the results of others (45, 46, 47) suggest that the IXXII
motif is important for recognition of the unliganded TR surface.
However, homologies between N-CoR ID3, N-CoR ID2, and SMRT ID2 and
N-CoR and SMRT ID1 extend beyond the conserved hydrophobic core (Fig. 1), and we, and others (45, 46, 47), found that mutations within these
adjoining residues disrupted TR/N-CoR interactions. Thus, the IDs are
composed of both the hydrophobic core and adjacent sequences. We also
know that key residues for both coactivator and corepressor binding lie
within the nuclear receptor hydrophobic cleft (43, 44, 45, 46, 47, 49) and that
helix 12 forms a key part of the AF-2 surface (39, 40, 41), but is
dispensable or inhibitory for corepressor interactions (19, 45, 46, 47, 50, 51). Thus, it is likely that the choice between coactivator and
corepressor binding is regulated by ligand-dependent repositioning of
helix 12. Indeed, in the unliganded RXR-LBD crystal structure (52),
helix 12 extends away from the LBD rather than packing against the LBD
as in the T3-liganded TR (33). We therefore
propose that the conserved I/LXXII motif binds to a region of the cleft
that lies under helix 12 and is exposed by the repositioning of
helix 12 in the unliganded state and that TR/N-CoR interactions are
stabilized by interaction of adjoining sequences from the IDs with the
TRß surface.
Our results also give some indication that the structure of the N-CoR
ID motif may be different from the structure of the NR box. First, the
central hydrophobic residues of both motifs are important for TR
binding, but adjoining ID sequences play a more important role than
adjoining NR box sequences (39, 53). Second, while the NR boxes adopt a
two- turn -helical structure (39, 40, 41), the IDs are longer and the
position of some of the TR binding residues is inconsistent with a
location on one face of an extended -helix. Lastly, one of the
nonhydrophobic residues within the ID1 core motif (LDVII)
is required for ID1 peptide competitions (Fig. 7). The nonhydrophobic
residues of the NR box core do not play a role in TR binding (39).
There may also be subtle differences in the way that the TR recognizes
distinct IDs. N-CoR ID1, but not ID2 or ID3, shows weak residual
hormone-independent binding to TR in two-hybrid assays. Moreover, the
region of best homology between N-CoR ID3, ID2, and SMRT ID2 lies
N-terminal to the core motif, and the area of best conservation between
N-CoR and SMRT ID1 lies C terminal to the core motif (Fig. 1).
Recombining these two areas of conservation creates an artificial
hybrid peptide that competes very efficiently for TR/N-CoR interactions
(Fig. 7C). Similar increases in TR binding efficiency have also been
obtained when distinct IDs are recombined and tested in two-hybrid
assays (45). Together, these results are consistent with the notion
that distinct adjoining sequences from different IDs make distinct
contacts with the TR surface. While we do not know what these contacts
are, one possibility is that the Leu-Met pair at the C terminus of ID1
(KALM) could bind to the upper part of the hydrophobic
cleft, with the LM in a similar position to the C-terminal leucines
(LXXLL) of the NR box (39). This interaction could also
have analogies to the way that estrogen receptor helix 12 folds into
the same region of the cleft in the presence of antiestrogens (40, 54)
and account for the weak ligand-independent component of TRß/ID1
interactions. It is likely that the full understanding of TRß/N-CoR
interactions will require resolution of TRß/N-CoR crystal structures.
We speculate that it may be possible to take advantage of synthetic
peptides, including the ID3/ID1 hybrid described here, for this x-ray
structural analysis.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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Gal-N-CoR expression vectors were derived from the pM expression vector for the yeast Gal4 DNA-binding domain (CLONTECH Laboratories, Inc. Palo Alto, CA). N-CoR fragments were amplified by standard PCR methods. All 5'- oligonucleotides contained an EcoRI site for cloning. For Gal-N-CoR/1,925–2,308 the 3'-oligonucleotide contained a SalI site. The others were generated with a 3'-oligonucleotide that contained a HinDIII site. Similar Gal-N-CoR expression vectors with mutated ID sequences were generated using pSG5-N-CoR ID triple mutant as a template. GAL-RE-TK-luciferase was prepared by cloning a double-stranded oligonucleotide containing two copies of the GAL4 dimer binding site upstream of the fusion reporter gene containing the Herpes simplex virus thymidine kinase promoter (-109/+48) linked to the firefly luciferase gene.
The following plasmids have been previously described: GST-GRIP1 (563–1,121) (37), GST-TRß (55), Gal-RE-e1b- luciferase (37), cytomegalovirus (CMV)-TRß (32). The following were gifts: GST-N-CoR fusions 1,944–2,453 and 1,744–2,453 from Dr. M. Lazar (University of Pennsylvania School of Medicine, Philadelphia, PA), VP16-TRß from Dr. R. Evans (University of California San Diego, San Diego, CA), Gal-TRß from Dr. D. Moore (Baylor College of Medicine, Houston, TX), actin-ß-galactosidase from Dr. M. Garabedian (New York University, New York, NY).
Protein-Protein Interaction Assays
Labeled proteins, peptides, and GST fusion proteins were
prepared as previously described (37, 39). Peptide sequences were
as follows, ID1:- N-ASNLGLEDIIRKALMGSFDD-C; ID2:-
N-RTHRLITLADHICQIITQDFARNQ-C; ID3 N-RGKTTITAANFI-DVIITRQIASDK-C;
ID3/1 hybrid peptide:- N-RGKTTITAA NFI-
EDIIRKALMGSFDD-C.
Cell Culture and Transfections
Chicken embryo fibroblasts (CEF, UCSF Cell Culture Facility)
were grown in DMEM/F-12 Ham’s modified mix, without phenol red,
supplemented with 10% iron- supplemented newborn calf serum
(Sigma, St. Louis, MO) and pen-strep. CEF cells were
transfected, by electroporation (56), with 2 µg reporters, 1 µg of
Gal fusion protein expression vector or CMV vector control and, where
indicated, 5 µg of N-CoR or pSG5 control or 50 ng of TRß-VP16.
After electroporation, the cells were resuspended in medium containing
10% T3-depleted newborn calf serum. Luciferase
and ß-galactosidase activities were measured, using standard assays
(Promega Corp., Madison, WI; and Tropix, Bedford, MA) at
36–48 h. Individual transfections (containing data from triplicate
wells) were repeated three to six times.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Supported by NIH Grants DK-32129 and CA-30913 to P.J.K. Peter J. Kushner is a shareholder and Director of KaroBio AB, a company with commercial interests in this area of research. John D. Baxter has proprietary interests in, and serves as a consultant to and deputy director of, KaroBio AB.
Received for publication May 22, 2000. Revision received August 28, 2000. Accepted for publication August 30, 2000.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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. Nature 395:137–143[CrossRef][Medline]
. Mol Endocrinol 12:248–262. Nature 375:377–382[CrossRef][Medline]
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B. A. Jonas, N. Varlakhanova, F. Hayakawa, M. Goodson, and M. L. Privalsky Response of SMRT (Silencing Mediator of Retinoic Acid and Thyroid Hormone Receptor) and N-CoR (Nuclear Receptor Corepressor) Corepressors to Mitogen-Activated Protein Kinase Kinase Kinase Cascades Is Determined by Alternative mRNA Splicing Mol. Endocrinol., August 1, 2007; 21(8): 1924 - 1939. [Abstract] [Full Text] [PDF]
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 H. Yasumoto, L. Meng, T. Lin, Q. Zhu, and R. Y. L. Tsai GNL3L inhibits activity of estrogen-related receptor {gamma} by competing for coactivator binding J. Cell Sci., August 1, 2007; 120(15): 2532 - 2543. [Abstract] [Full Text] [PDF]
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 Y. Wu, H. Kawate, K. Ohnaka, H. Nawata, and R. Takayanagi Nuclear Compartmentalization of N-CoR and Its Interactions with Steroid Receptors. Mol. Cell. Biol., September 1, 2006; 26(17): 6633 - 6655. [Abstract] [Full Text] [PDF]
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 M. G. Rosenfeld, V. V. Lunyak, and C. K. Glass Sensors and signals: a coactivator/corepressor/epigenetic code for integrating signal-dependent programs of transcriptional response Genes & Dev., June 1, 2006; 20(11): 1405 - 1428. [Abstract] [Full Text] [PDF]
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 S. Nagpal, S. Na, and R. Rathnachalam Noncalcemic Actions of Vitamin D Receptor Ligands Endocr. Rev., August 1, 2005; 26(5): 662 - 687. [Abstract] [Full Text] [PDF]
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T. Ishizuka and M. A. Lazar The Nuclear Receptor Corepressor Deacetylase Activating Domain Is Essential for Repression by Thyroid Hormone Receptor Mol. Endocrinol., June 1, 2005; 19(6): 1443 - 1451. [Abstract] [Full Text] [PDF]
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X. Meng, P. Webb, Y.-F. Yang, M. Shuen, A. F. Yousef, J. D. Baxter, J. S. Mymryk, and P. G. Walfish E1A and a nuclear receptor corepressor splice variant (N-CoRI) are thyroid hormone receptor coactivators that bind in the corepressor mode PNAS, May 3, 2005; 102(18): 6267 - 6272. [Abstract] [Full Text] [PDF]
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 C. Yu, K. Markan, K. A. Temple, D. Deplewski, M. J. Brady, and R. N. Cohen The Nuclear Receptor Corepressors NCoR and SMRT Decrease Peroxisome Proliferator-activated Receptor {gamma} Transcriptional Activity and Repress 3T3-L1 Adipogenesis J. Biol. Chem., April 8, 2005; 280(14): 13600 - 13605. [Abstract] [Full Text] [PDF]
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S. Lee and M. L. Privalsky Heterodimers of Retinoic Acid Receptors and Thyroid Hormone Receptors Display Unique Combinatorial Regulatory Properties Mol. Endocrinol., April 1, 2005; 19(4): 863 - 878. [Abstract] [Full Text] [PDF]
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M. L. Goodson, B. A. Jonas, and M. L. Privalsky Alternative mRNA Splicing of SMRT Creates Functional Diversity by Generating Corepressor Isoforms with Different Affinities for Different Nuclear Receptors J. Biol. Chem., March 4, 2005; 280(9): 7493 - 7503. [Abstract] [Full Text] [PDF]
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M. C. Hodgson, I. Astapova, S. Cheng, L. J. Lee, M. C. Verhoeven, E. Choi, S. P. Balk, and A. N. Hollenberg The Androgen Receptor Recruits Nuclear Receptor CoRepressor (N-CoR) in the Presence of Mifepristone via Its N and C Termini Revealing a Novel Molecular Mechanism for Androgen Receptor Antagonists J. Biol. Chem., February 25, 2005; 280(8): 6511 - 6519. [Abstract] [Full Text] [PDF]
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D. R. Buchholz, A. Tomita, L. Fu, B. D. Paul, and Y.-B. Shi Transgenic Analysis Reveals that Thyroid Hormone Receptor Is Sufficient To Mediate the Thyroid Hormone Signal in Frog Metamorphosis Mol. Cell. Biol., October 15, 2004; 24(20): 9026 - 9037. [Abstract] [Full Text] [PDF]
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S. Ogawa, J. Lozach, K. Jepsen, D. Sawka-Verhelle, V. Perissi, R. Sasik, D. W. Rose, R. S. Johnson, M. G. Rosenfeld, and C. K. Glass A nuclear receptor corepressor transcriptional checkpoint controlling activator protein 1-dependent gene networks required for macrophage activation PNAS, October 5, 2004; 101(40): 14461 - 14466. [Abstract] [Full Text] [PDF]
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 M. Malartre, S. Short, and C. Sharpe Alternative splicing generates multiple SMRT transcripts encoding conserved repressor domains linked to variable transcription factor interaction domains Nucleic Acids Res., September 1, 2004; 32(15): 4676 - 4686. [Abstract] [Full Text] [PDF]
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Q. Wang, J. A. Blackford Jr., L.-N. Song, Y. Huang, S. Cho, and S. S. Simons Jr. Equilibrium Interactions of Corepressors and Coactivators with Agonist and Antagonist Complexes of Glucocorticoid Receptors Mol. Endocrinol., June 1, 2004; 18(6): 1376 - 1395. [Abstract] [Full Text] [PDF]
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L. Pascual-Le Tallec, O. Kirsh, M.-C. Lecomte, S. Viengchareun, M.-C. Zennaro, A. Dejean, and M. Lombes Protein Inhibitor of Activated Signal Transducer and Activator of Transcription 1 Interacts with the N-Terminal Domain of Mineralocorticoid Receptor and Represses Its Transcriptional Activity: Implication of Small Ubiquitin-Related Modifier 1 Modification Mol. Endocrinol., December 1, 2003; 17(12): 2529 - 2542. [Abstract] [Full Text] [PDF]
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T. Ishizuka and M. A. Lazar The N-CoR/Histone Deacetylase 3 Complex Is Required for Repression by Thyroid Hormone Receptor Mol. Cell. Biol., August 1, 2003; 23(15): 5122 - 5131. [Abstract] [Full Text] [PDF]
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X. Hu, S. Li, J. Wu, C. Xia, and D. S. Lala Liver X Receptors Interact with Corepressors to Regulate Gene Expression Mol. Endocrinol., June 1, 2003; 17(6): 1019 - 1026. [Abstract] [Full Text] [PDF]
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F. Liang, P. Webb, A. Marimuthu, S. Zhang, and D. G. Gardner Triiodothyronine Increases Brain Natriuretic Peptide (BNP) Gene Transcription and Amplifies Endothelin-dependent BNP Gene Transcription and Hypertrophy in Neonatal Rat Ventricular Myocytes J. Biol. Chem., April 18, 2003; 278(17): 15073 - 15083. [Abstract] [Full Text] [PDF]
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H.-Y. Kao, C. C. Han, A. A. Komar, and R. M. Evans Co-repressor Release but Not Ligand Binding Is a Prerequisite for Transcription Activation by Human Retinoid Acid Receptor alpha Ligand-binding Domain J. Biol. Chem., February 28, 2003; 278(9): 7366 - 7373. [Abstract] [Full Text] [PDF]
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P. Webb, P. Nguyen, and P. J. Kushner Differential SERM Effects on Corepressor Binding Dictate ERalpha Activity in Vivo J. Biol. Chem., February 21, 2003; 278(9): 6912 - 6920. [Abstract] [Full Text] [PDF]
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Y. Yang, X. Wang, T. Dong, E. Kim, W.-J. Lin, and C. Chang Identification of a Novel Testicular Orphan Receptor-4 (TR4)-associated Protein as Repressor for the Selective Suppression of TR4-mediated Transactivation J. Biol. Chem., February 21, 2003; 278(9): 7709 - 7717. [Abstract] [Full Text] [PDF]
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A. Makowski, S. Brzostek, R. N. Cohen, and A. N. Hollenberg Determination of Nuclear Receptor Corepressor Interactions with the Thyroid Hormone Receptor Mol. Endocrinol., February 1, 2003; 17(2): 273 - 286. [Abstract] [Full Text] [PDF]
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B. R. Huber, M. Desclozeaux, B. L. West, S. T. Cunha-Lima, H. T. Nguyen, J. D. Baxter, H. A. Ingraham, and R. J. Fletterick Thyroid Hormone Receptor-{beta} Mutations Conferring Hormone Resistance and Reduced Corepressor Release Exhibit Decreased Stability in the N-Terminal Ligand-Binding Domain Mol. Endocrinol., January 1, 2003; 17(1): 107 - 116. [Abstract] [Full Text] [PDF]
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L. M. Sachs, P. L. Jones, E. Havis, N. Rouse, B. A. Demeneix, and Y.-B. Shi Nuclear Receptor Corepressor Recruitment by Unliganded Thyroid Hormone Receptor in Gene Repression during Xenopus laevis Development Mol. Cell. Biol., December 15, 2002; 22(24): 8527 - 8538. [Abstract] [Full Text] [PDF]
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M. Desclozeaux, I. N. Krylova, F. Horn, R. J. Fletterick, and H. A. Ingraham Phosphorylation and Intramolecular Stabilization of the Ligand Binding Domain in the Nuclear Receptor Steroidogenic Factor 1 Mol. Cell. Biol., October 15, 2002; 22(20): 7193 - 7203. [Abstract] [Full Text] [PDF]
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A. Takeshita, M. Taguchi, N. Koibuchi, and Y. Ozawa Putative Role of the Orphan Nuclear Receptor SXR (Steroid and Xenobiotic Receptor) in the Mechanism of CYP3A4 Inhibition by Xenobiotics J. Biol. Chem., August 30, 2002; 277(36): 32453 - 32458. [Abstract] [Full Text] [PDF]
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M. Schulz, M. Eggert, A. Baniahmad, A. Dostert, T. Heinzel, and R. Renkawitz RU486-induced Glucocorticoid Receptor Agonism Is Controlled by the Receptor N Terminus and by Corepressor Binding J. Biol. Chem., July 12, 2002; 277(29): 26238 - 26243. [Abstract] [Full Text] [PDF]
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S. Cheng, S. Brzostek, S. R. Lee, A. N. Hollenberg, and S. P. Balk Inhibition of the Dihydrotestosterone-Activated Androgen Receptor by Nuclear Receptor Corepressor Mol. Endocrinol., July 1, 2002; 16(7): 1492 - 1501. [Abstract] [Full Text] [PDF]
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A. Marimuthu, W. Feng, T. Tagami, H. Nguyen, J. L. Jameson, R. J. Fletterick, J. D. Baxter, and B. L. West TR Surfaces and Conformations Required to Bind Nuclear Receptor Corepressor Mol. Endocrinol., February 1, 2002; 16(2): 271 - 286. [Abstract] [Full Text] [PDF]
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G. B. Potter, G. M.J. Beaudoin III, C. L. DeRenzo, J. M. Zarach, S. H. Chen, and C. C. Thompson The hairless gene mutated in congenital hair loss disorders encodes a novel nuclear receptor corepressor Genes & Dev., October 15, 2001; 15(20): 2687 - 2701. [Abstract] [Full Text] [PDF]
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R. N. Cohen, S. Brzostek, B. Kim, M. Chorev, F. E. Wondisford, and A. N. Hollenberg The Specificity of Interactions between Nuclear Hormone Receptors and Corepressors Is Mediated by Distinct Amino Acid Sequences within the Interacting Domains Mol. Endocrinol., July 1, 2001; 15(7): 1049 - 1061. [Abstract] [Full Text] [PDF]
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