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2 Is a Weak Antagonist because It Is Deficient in Interactions with Nuclear Receptor Corepressors1
Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Chicago, Illinois 60611
Address all correspondence and requests for reprints to: J. Larry Jameson, M.D., Ph.D., Division of Endocrinology, Metabolism, and Molecular Medicine, Northwestern University Medical School, Tarry 15–709, 303 East Chicago Avenue, Chicago, Illinois 60611. E-mail: ljameson{at}nwu.edu
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Abstract |
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2, is unable to bind
thyroid hormone (T3) and has been proposed to function as
an endogenous inhibitor of T3 action. In this report, we
examined further the DNA sequence requirements for 2 binding to
thyroid hormone response elements (TREs) in an attempt to identify
response elements that mediate potent inhibition by 2. Heterodimers
of 2 and retinoid X receptor were found to bind to a subset of TREs
(DR4, direct repeats spaced by 4 bp) in which selected flanking and
spacer sequences enhanced interactions with the AGGTCA core binding
sequence. Despite the optimization of the TRE-binding sites, 2
remained a weak dominant negative inhibitor of TRE-driven
transcription. A promoter interference assay was also developed for
testing inhibition by 2. In these studies, 2 blocked gene
transcription, but it required cotransfected retinoid X receptor, and
it was not as potent as unliganded thyroid hormone receptors. These
results led to the hypothesis that 2 might be deficient in
interactions with nuclear receptor corepressors. Consistent with this
view, 2 did not silence basal transcription in its native form or
when linked to Gal4. 2 also failed to interact with corepressors
(NCoR and SMRT) in both gel shift assays and mammalian two-hybrid
assays. We conclude that 2 is a weak antagonist of thyroid hormone
action because it binds weakly to a limited repertoire of response
elements, and it does not interact with corepressors. Thus, 2 may be
able to compete with thyroid hormone receptors for binding to a limited
group of target sites, but it is not able to actively inhibit
transcription. |
Introduction |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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and ß, encode the TRs, which
are expressed as several isoforms due to alternative splicing (2). TRs
exhibit a modular structure with functionally separable domains. The
DNA-binding domain (DBD) and the ligand-binding domain (LBD) of the TRs
are highly conserved. The LBD is involved in homo- and
heterodimerization (3) and in transcriptional activation or repression
through interactions of the TR with coactivators or corepressors (CoRs)
(4, 5, 6). TRs bind to thyroid hormone response elements (TREs) in the promoter regions of target genes, thereby conferring ligand-dependent transcriptional regulation. TRs bind to TREs as monomers, homodimers, or heterodimers with accessory proteins, in particular the retinoid X receptors (RXRs) (3). The minimal target sequence defining the TRE half-site consists of the hexameric sequence, AGGTCA (7), or the optimized octameric element (T/C)(A/G)AGGTCA (8). This core recognition motif can be present as a single half-site, as two half-sites arranged as a direct repeat spaced by 4 bp (DR4), as a palindrome (PAL), or as an inverted palindrome (LAP) (1).
The splice variant of the gene, referred to as 2, is identical
to TR1 for the first 370 amino acids, but the carboxyl-terminal
40 amino acids are replaced by an entirely distinct sequence of 122
residues. This results in an inability of 2 to bind hormone and to
function as a T3-dependent transcription factor
(9, 10, 11). 2 is missing the carboxyl-terminal part of the so-called
ninth hydrophobic heptad, and its ability to form heterodimers and to
bind to DNA is therefore profoundly altered (12, 13, 14). In gel-shift
experiments, 2-RXR heterodimers bind to a subset of DR4 TREs, but
not to PAL or LAP TREs (15).
The physiological role of 2 remains to be elucidated. It is highly
expressed in several tissues, including brain, kidney, and testis (16).
As the metabolic effects of T3 are relatively
modest in these tissues, it has been proposed that 2 could play a
role as an endogenous antagonist. However, in transient expression
assays, the inhibitory activity of 2 is relatively weak, at least
when compared with the dominant negative activity of mutant TRs that
occur in patients with resistance to thyroid hormone (RTH) (11, 17, 18). The relatively weak nature of 2 inhibitory activity is only
partially explained by its decreased binding to TREs (19).
It has been shown recently that the dominant negative activity of RTH
mutants requires interactions with CoRs (20, 21). We report here that
the weak dominant negative activity of 2 may be caused in part by
its lack of interaction with CoRs.
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Materials and Methods |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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. In all synthetic TREs, the core
half-site consists of the consensus hexamer AGGTCA (3) or the expanded
octamer TAAGGTCA (8).
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were
subcloned into pGEM7 (Promega, Madison, WI) for in vitro
transcription and translation and into a Rous sarcoma virus vector for
transient expression in transfected cells (23). The Gal4 constructs for
the different TR isoforms and hRXR contain the LBD of the receptor
downstream of the Gal4 DBD in-frame in pSG424 (24). The pCMX-NCoR
construct was provided by M. G. Rosenfeld (University of
California, San Diego, CA) (5), and pCMX-SMRT was a gift from R.
M. Evans (Salk Institute, San Diego, CA) (4). The pCMX-NCoR-ID (ID,
interaction domain; internal ATG at amino acid 1579) expression vector
was created by deleting the NotI-BstXI fragment
from pCMX-NCoR. VP16-NCoR-ID and VP16-SMRT-ID contain the TR
interaction domain of NCoR (residues 1552–2453) and that of SMRT
(residues 876-1495) downstream of the VP16 activation domain in pAASV
(25).
Reporter gene constructs were created by inserting annealed synthetic
oligonucleotides upstream of the indicated minimal promoters. The
plasmid DR4-SV40-Luc contains four copies of a direct repeat TRE
(5'-agcttcAGGTCActtcAGGTCActcga-3') upstream of the simian virus 40
(SV40) promoter in the pGL3 luciferase vector (Promega, Madison, WI).
PAL-TK-Luc contains two copies of a palindromic TRE
(5'-gatctcAGGTCATGACCTgagatc-3') upstream of a thymidine kinase
promoter (TK109) in the pA3 luciferase vector (26). The Gal4 reporter
plasmid, UAS-TK-Luc, contains two copies of the Gal4 recognition
sequence (UAS) upstream of TK109 in pA3-Luc. For the promoter
interference assays, a glucocorticoid response element was inserted
upstream of TK109. Various TR-binding sites (a DR4 TRE binding 2/RXR
heterodimers and a DR4 unable to bind the heterodimer, as well as an
everted and inverted palindromic TRE) were inserted between the TATA
box of the promoter and the transcription initiation site (27, 28).
DNA binding studies
Gel mobility shift assays were performed to assess DNA binding
and dimerization properties in vitro. TR isoforms, RXR,
and NCoR-ID were transcribed and translated using the TNT-coupled
reticulolysate system (Promega). Lysates expressing TR (2.5 µl), in
the presence or absence of RXR (2.5 µl), or NCoR-ID (3 µl) were
preincubated at room temperature in a 25-µl reaction with a binding
buffer consisting of 20 mM HEPES (pH 7.8), 50
mM KCl, 1 mM EDTA, 10% glycerol, 1
mM dithiothreitol (DTT), and 50 µg/ml poly(dI-dC) for 10
min. 32P-Labeled TREs were added, and the mixture was
incubated for an additional 20 min. The protein-DNA complexes were
analyzed by electrophoresis through a 5% polyacrylamide gel containing
2.5% glycerol in 0.5 x TBE (45 mM Tris-borate and 1
mM EDTA).
Whole cell lysates from TSA-201 cells transfected with 1 µg TR expression plasmids were prepared by three cycles of freeze-thaw lysis in 20 mM Tris-HCl (pH 7.5), 0.5 M KCl, 2 mM DTT, 20% glycerol, and 1 mM phenylmethylsulfonylfluoride. Cell extracts were prepared by centrifugation at 10,000 x g for 30 min at 4 C, and supernatants were stored at -20 C. Cell extracts (10 µg) were incubated with 32P-labeled DR4-A TRE oligonucleotides in 24 µl of a modified binding buffer [20 mM HEPES (pH 7.8), 100 mM KCl, 1 mM EDTA, 20% glycerol, 1 mM DTT, and 100 µg/ml poly dI-dC] at 4 C.
For dissociation kinetics of TR-RXR complexes, a 100-fold excess of cold TRE oligonucleotide was added at various time points before initiating electrophoresis (26).
Transient expression assays
TSA-201 cells, a clone of human embryonic kidney 293 cells (29),
were grown in DMEM containing 10% FBS, penicillin (100 U/ml), and
streptomycin (100 µg/ml) and transfected by the calcium phosphate
method as previously described (26). The total amount of expression
plasmid DNA was kept constant in the different experimental groups by
adding corresponding amounts of the same plasmids without receptor.
After exposure to the calcium phosphate-DNA precipitate for 8 h,
Opti-MEM (Life Technologies, Grand Island, NY) with 4% Dowex
resin-stripped FBS was added, with or without 10 nM
T3. Cells were harvested after 40 h for
measurement of luciferase activity (30).
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Results |
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1, and 2 were studied in the absence and presence of RXR using
gel mobility shift assays. Seven synthetic and five naturally occurring
TREs were studied in an effort to identify TREs that bind 2
relatively well. An example of TRE (DR4-A) that binds 2/RXR
heterodimers is shown in Fig. 1A. This
TRE binds TRß1 and TR1 as homodimers, and in the presence of RXR,
the majority of the TR exists as a TR/RXR heterodimer. 2 binds to
DR4-A as a heterodimer with RXR, but no 2 homodimer is seen,
suggesting that interactions with RXR are required to form stable 2
complexes. An example of a TRE (DR4-E) that does not bind 2 is shown
in Fig. 1B. In contrast to DR4-A, 2 does not bind to DR4-E even in
the presence of RXR. Although the DR4-E binds TRß1 and TR1 well as
heterodimers, it binds these receptors poorly as homodimers.
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) were able to bind 2/RXR heterodimers, but
five other DR4 TREs were unable to bind this complex under the
conditions of the gel shift assay (middle group in Table 1).
Certain features are shared among the TRE sequences that are permissive
for binding 2/RXR heterodimers. For example, the DR4 sequences that
bind 2/RXR also bind TRß1 and TR1 homodimers (with the
exception of the Moloney leukemia virus TRE). In contrast, the DR4 TREs
that are not able to bind 2/RXR heterodimers, bind TRß1/RXR and
TR1/RXR as heterodimers, but do not exhibit monomer or homodimer
binding. Thus, there is a correlation between the ability to bind
receptors as homodimers and the ability to bind 2/RXR
heterodimers.
The hexameric core motif, AGGTCA, has been preserved in each of the
artificially configured TREs. Consistent with the proposed optimal
half-site for TR1, which is formed by the octameric sequence
(T/C)(A/G)AGGTCA (8), a thymidine is present 2 bp 5' of the hexameric
AGGTCA motif in both half-sites in all but one of the 2 permissive
TREs in the upper group of Table 1. A single TRE (DR4-B in
Table 1) contains a thymidine at this position in the 5' half-site, but
a cytosine in the downstream half-site. The first nucleotide upstream
of the hexameric half-site was occupied by either a cytosine or an
adenosine. In each of the TREs that bind the 2/RXR heterodimers,
guanosines are absent in the spacer regions between the half-sites,
whereas the nonbinding DR4s each contain guanosines within the spacer.
With the exception of the one synthetic element in the nonbinding DR4s
(DR4-E, Fig. 1B), the hexameric half-sites deviate from the idealized
sequence, AGGTCA. Moreover, a TA or TC motif upstream of the half-sites
is absent in each of them, with the exception of the rat GH TRE (31).
Taken together, these experiments reveal that 2/RXR binds a limited
number of idealized TREs, and that these elements generally correspond
to sequences that also bind TR monomers and homodimers.
Dissociation kinetics of TR/RXR complexes from a DR4 TRE
Although 2/RXR complexes readily bind to idealized elements
such as DR4-A, it is possible to analyze the stability of these
complexes by determining dissociation rates. After binding complexes
have formed, the addition of a large excess of unlabeled TRE allows the
rates of dissociation to be estimated, as any unbound receptor will
most likely rebind to unlabeled DNA (26). Under these conditions,
TRß1/RXR and TR1/RXR heterodimer complexes are relatively stable
(Fig. 1C). Even after 90 min, little receptor has dissociated. In
contrast, the 2/RXR heterodimers dissociate rapidly, showing greater
than 50% dissociation by 30 min. These experiments indicate that
although abundant 2/RXR complex is seen in the standard gel-shift
assay, the 2/RXR heterodimers are relatively unstable compared with
the TRß1/RXR and TR1/RXR heterodimers.
Dominant negative inhibition by 2/RXR heterodimers
The variable ability of 2/RXR heterodimers to bind different
TREs led to the hypothesis that the degree of 2 inhibition might
differ using binding and nonbinding TREs (15). The functional effects
of 2/RXR heterodimers were assessed using reporter genes containing
an 2-binding TRE (DR4-A) or an 2-nonbinding TRE (PAL). Using
DR4-SV40-Luc, a 10-fold excess of 2 weakly inhibited
TRß1-regulated (13-fold decreased to 11-fold) or TR1-regulated
(13-fold decreased to 8-fold) expression (Fig. 2A). By comparison, a dominant negative
mutant of TRß1 (P453X), which contains a nine-amino acid deletion at
the carboxyl-terminus (22), strongly inhibited both TRß1-regulated
(13-fold decreased to 4-fold) and TR1-regulated (13-fold decreased
to 2-fold) expression. Unexpectedly, the inhibitory effect of 2 was
nearly identical to that of the nonbinding TRE reporter gene,
PAL-TK-Luc (Fig. 2B). These results indicate that while 2 is a weak
inhibitor of TR-mediated expression, its effects correlate poorly with
its ability to bind TREs in vitro.
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2 and other TR isoforms in transfected TSA-201 cells (26). The DR4-A
TRE was used as a labeled probe because it binds well to each of the TR
isoforms. As shown in Fig. 3, comparable
amounts of TR1, TRß1, 2, and the P453X mutant were detected in
the transfected cells. The complexes migrated in parallel with in
vitro translated TR/RXR heterodimers, and no receptor bands were
seen in mock-transfected cells. These results suggest that the weak
dominant negative activity of 2 is not caused by low levels of
expression in transfected cells.
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2 inhibited reporter genes independent of
its ability to bind 2/RXR led us to use an independent assay for
2 interactions with DNA in vivo. In the promoter
interference assay, various TREs were inserted adjacent to the site of
transcriptional initiation, resulting in transcriptional inhibition
when receptors bound to these elements (27, 28) (Fig. 4). The results using the DR4-A TRE
(which binds 2-RXR well) inserted into the promoter are shown in
Fig. 4A. The construct was stimulated by the glucocorticoid receptor in
the presence of 100 nM dexamethasone, reflecting the
presence of the upstream glucocorticoid response element. Expression of
TRß1 or TR1 markedly repressed activity, even in the absence of
RXR. In contrast, little repression was seen with 2 alone.
Consistent with its requirement for RXR to bind DR4-A, coexpression of
2 and RXR caused a greater degree of inhibition, but still less than
that observed with TRß1 or TR1. DBD mutants of TRß1 do not
inhibit this construct (28), and none of the receptors caused
inhibition of a control promoter without a TRE (data not shown). In
Fig. 4B, the results are shown using a promoter containing a DR4 TRE
(DR4-E) that is unable to bind 2/RXR heterodimers when examined in
gel-shift assays. The results are similar to those using the permissive
TRE (DR4-A). Although little inhibition was seen with 2 alone,
addition of RXR induced partial suppression, but less than that seen
with TRß1 and TR1. Similarly, 2 and RXR caused partial
suppression of TRE-Pal (Fig. 4C). Although it is possible that the
effects of 2 and RXR are independent, these results suggest that
they may form heterodimers that are able to weakly bind some TRE
elements in vivo, even when binding is not detected in
gel-shift assays.
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2 and Gal4-22 might
reflect diminished or absent binding of NCoRs. Because NCoRs are
required for basal repression by unliganded receptors, the silencing
activities of TR isoforms were examined using two different types of
reporter genes [DR4(A)-SV40-Luc and PAL-TK-Luc]. When TR1 or
TRß1 isoforms were transfected into TSA-201 cells together with the
positively regulated genes, pronounced silencing was observed in the
unliganded state (without T3) for both types of
reporter genes (Fig. 5, A and B). In
contrast, minimal silencing was observed with 2. Cotransfection of
RXR had little effect on the degree of repression. Silencing was
also examined using Gal4-TR constructs (24). Gal4-TR1 and Gal4-TRß
strongly silenced expression (90% and 75% repression, respectively)
from UAS-TK-Luc compared with the Gal4-DBD alone (Fig. 5C). As with the
native receptors, the silencing activity of Gal4-2 was greatly
reduced relative to those of the Gal4-TR1 and Gal4-TRß
constructs.
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2 interactions with NCoR and SMRT, incubation of in
vitro translated NCoR-ID with TR1 (lanes 3) or TRß (lanes 5)
generated a slower migrating band corresponding to a complex between
NCoR-ID and TR. A control using NCoR-ID in the absence of TR showed no
binding to the DR4 element (lane 1). As noted previously (21),
T3 dissociated the TR homodimer complex and
prevented formation of the TR complex with NCoR-ID (data not shown). In
contrast to the TRs, no interaction was seen between NCoR-ID and 2
(lane 7).
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) or VP16-SMRT-ID
(Fig. 7B) in TSA-201 cells. Relative to the Gal4 DBD alone,
Gal4-TR1 and Gal4-TRß were stimulated 60- and 10-fold by
the addition of VP16-NCoR-ID and VP16-SMRT-ID, respectively. In
contrast, little or no stimulation by these VP16-CoR constructs was
seen using Gal4-2 or Gal4-RXR.
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Discussion |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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2 is
a weak antagonist because it fails to interact with CoRs. 2 has
impaired ability to interact with CoRs, as revealed by gel-shift assays
and mammalian two-hybrid interaction assays. Moreover, it is unable to
effectively silence basal transcription in its native form or when
linked to Gal4. The inhibitory activity of 2 was relatively
weak compared with that of a dominant negative mutant of TRß1.
Finally, even after the optimization of 2-binding sites using
gel-shift assays, 2 was shown to dissociate from TREs more readily
than TRß1 or TR1. Promoter interference assays also revealed that
2 does not bind as well as unliganded TRs. Thus, we propose that
2 is a relatively weak antagonist of TR-mediated action because it
binds weakly, even to optimized TREs, and because it fails to interact
with CoRs, which might otherwise strongly silence genes that bind
2.
2 is widely expressed, but its levels are particularly high in
brain, kidney, and testis (16). Because these tissues exhibit
relatively low metabolic responses to T3 (1),
2 has been proposed as a potential endogenous inhibitor of TR action
(9). Several studies have suggested that the inhibitory effect of 2
is caused by competition with TRs for binding to TREs (2, 15, 19, 34, 35, 36). Other results have provided evidence for DNA-independent
mechanisms for 2 inhibition (11, 19, 37, 38). Although 2 was
initially considered unable to bind to TREs (11, 39), we have shown
that it can bind as a heterodimer on certain direct repeat TREs (15).
Recently, this observation has been confirmed and extended by others
(19, 36), and it has been proposed that the binding of 2/RXR
heterodimer requires an optimized downstream octameric half-site.
This study further examines the sequence determinants that enable the
binding of 2/RXR heterodimers to DR4 TREs and its role as an
endogenous inhibitor. All synthetic TREs found to bind 2/RXR
heterodimers contain half-site sequences that are almost identical with
the optimal octameric sequence reported for TR1 (8). Of note, and in
contrast to the TRE, that are unable to bind 2/RXR heterodimers in
gel-shift experiments, most of these TREs also bound TRß1 as
homodimer, and TR1 as monomer and homodimer. It is likely that the
correlation of homodimer and 2/RXR heterodimer binding reflects
optimization of flanking and spacing sequences that surround the
hexameric TRE half-site. Binding of TR1 to a single octameric
half-site has been reported previously and has been shown to confer
T3 responsiveness to a heterologous promoter in
transient transfections (8). As shown previously by Reginato et
al. (36), we also found that 2 and RXR interactions are
relatively weak in mammalian two-hybrid assays (data not shown). The
loss of strong 2/RXR heterodimerization has been attributed to the
location of the 2 splice site (19, 36), which disrupts the so-called
ninth heptad repeat, a region known to be involved in receptor
dimerization (15, 40, 41). Thus, the DNA sequence of the TRE may play a
particularly important role in the stabilization of the 2/RXR
heterodimer. The finding that guanosines in the spacer region between
the half-sites abolished the formation of 2/RXR indicates that in
addition to providing an optimized downstream half-site, the
composition of the spacer region is also of importance for stabilizing
the 2/RXR heterodimer. Despite the optimization of 2/RXR binding,
studies of dissociation kinetics reveal that the 2/RXR complex is
relatively unstable compared with TRß1/RXR and TR1/RXR
heterodimers.
The silencing function of TR and RAR has been shown to be mediated by
CoRs (4, 5). These proteins interact with the unliganded form of the
receptors and bind near the hinge region between the DBD and the
carboxyl-terminal LBD. In earlier studies, it was noted that the TR
contains a transferable silencing domain in its carboxyl-terminus (42),
and that RTH mutants retain this silencing function in a constitutive
manner that is not reversed by T3 (43). This
finding raised the possibility that in addition to competition with
wild-type TR for TRE-binding sites (26), RTH mutants might actively
repress target genes. Subsequent studies confirmed basal silencing of
positively regulated promoters by RTH mutants (44). The identification
of CoRs and their interaction domains within the TR (4, 5, 45) has
allowed their role in RTH to be assessed more directly. It was
demonstrated that insertion of TR mutations that disrupt interactions
with CoR greatly reduced the dominant negative activity of the RTH
mutants (20, 21). Busch et al. (46) identified at least
three subdomains of v-erbA that are involved in its
silencing function. In the TRß1, mutations of K420E and K424E in the
ninth heptad also affected silencing. Although the interaction surface
of TRs with CoRs is not well characterized, the present study suggests
that the ninth heptad region that is disrupted in 2 is also critical
for CoR interaction and for silencing.
The absence of CoR interactions with 2 partially explains its weak
inhibitory activity. Competitive DNA binding remains, however, a
mechanism for the residual inhibitory effect of 2. The ability of
the 2/RXR heterodimer to inhibit transcription by binding to DNA is
supported by the experiments using the promoter interference approach.
Although promoter interference by 2 is relatively weak, it was
enhanced by coexpression of RXR. Binding of the transcriptionally
inactive 2 may account in part for its weak dominant negative
activity. However, it should be noted that a DBD mutant of 2 only
partially eliminates the dominant negative effect of 2 on various
TREs (15, 37, 38). These findings are consistent with inhibitory
effects of 2 that occur independent of DNA binding (11, 19, 37, 38).
It is unlikely that the inhibition by 2 is mediated by squelching
coactivators such as steroid receptor coactivator-1 (47), transcription
intermediary factor-2 (48), or CREB-binding protein/p300 (6), as 2
itself does not mediate trans-activation and lacks the
carboxyl-terminal activating function-2 domain. Alternatively, the TR
has been reported to interact with transcription factor IIB through its
amino-terminus, and this domain is intact in 2 (49).
A model for 2 action is presented in Fig. 8. As described above, the CoR interacts
with the wild-type TRs, such as 1 and ß, and induces
transcriptional silencing of the target gene in the absence of
T3. In contrast to RTH mutants, which bind CoRs
and induce potent silencing, 2 does not interact with CoRs and binds
to DNA weakly. At high levels, 2/RXR heterodimers might compete with
wild-type TRs for access to a subset of target genes and/or for binding
to general transcription factors. In view of this and other studies,
the mechanism of 2 action is becoming clearer. Ultimately, selective
2 gene knockouts or overexpression in transgenic mice may be
required to clarify its physiological role.
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Acknowledgments |
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Footnotes |
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2 T.T. and P.K. contributed equally to this work.
3 Recipient of a fellowship grant from the Swiss National Foundation
of Science.
Received November 5, 1997.
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References |
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TopAbstractIntroductionMaterials and MethodsResultsDiscussionReferences |
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1 with high
affinity. J Biol Chem 268:19392–19397 and ß forms for the acetic acid analog and
failure of the human testis and kidney products to bind T3.
Mol Endocrinol 4:227–2342. Role of the ninth heptad in DNA
binding, heterodimerization with retinoid X receptors, and dominant
negative activity. J Biol Chem 271:28235–28242-type c-erbA inhibits
trans-activation by thyroid hormone receptors without
binding thyroid hormone. Proc Natl Acad Sci USA 86:7771–77742) is due to
competition for binding sites on target genes. J Biol Chem 268:20904–209102 does not require binding to a thyroid
response element. Mol Endocrinol 9:86–952 and
peroxisome proliferator-activated receptor: evidence for different
mechanisms of inhibition. Mol Cell Endocrinol 107:55–66[CrossRef][Medline]
2, and thyroid hormone receptor 1 mediate
different DNA-binding and heterodimerization properties. Mol Endocrinol 6:805–814This article has been cited by other articles:
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B. Z. Doulabi, M. P.-T. Schiphorst, A. Kalsbeek, E. Fliers, O. Bakker, and W. M. Wiersinga Diurnal Variation in Rat Liver Thyroid Hormone Receptor (TR)-{alpha} Messenger Ribonucleic Acid (mRNA) Is Dependent on the Biological Clock in the Suprachiasmatic Nucleus, whereas Diurnal Variation of TR{beta}1 mRNA Is Modified by Food Intake Endocrinology, March 1, 2004; 145(3): 1284 - 1289. [Abstract] [Full Text] [PDF]
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 N. Vasudevan, S. Ogawa, and D. Pfaff Estrogen and Thyroid Hormone Receptor Interactions: Physiological Flexibility by Molecular Specificity Physiol Rev, October 1, 2002; 82(4): 923 - 944. [Abstract] [Full Text] [PDF]
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 C. Salto, J. M. Kindblom, C. Johansson, Z. Wang, H. Gullberg, K. Nordstrom, A. Mansen, C. Ohlsson, P. Thoren, D. Forrest, et al. Ablation of TR{alpha}2 and a Concomitant Overexpression of {alpha}1 Yields a Mixed Hypo- and Hyperthyroid Phenotype in Mice Mol. Endocrinol., December 1, 2001; 15(12): 2115 - 2128. [Abstract] [Full Text] [PDF]
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 L. Ng, A. Rusch, L. L. Amma, K. Nordstrom, L. C. Erway, B. Vennstrom, and D. Forrest Suppression of the deafness and thyroid dysfunction in Thrb-null mice by an independent mutation in the Thra thyroid hormone receptor {alpha} gene Hum. Mol. Genet., November 1, 2001; 10(23): 2701 - 2708. [Abstract] [Full Text] [PDF]
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K.-h. Lin and Y.-h. Wu shen-liang chen Impaired Interaction of Mutant Thyroid Hormone Receptors Associated with Human Hepatocellular Carcinoma with Transcriptional Coregulators Endocrinology, February 1, 2001; 142(2): 653 - 662. [Abstract] [Full Text] [PDF]
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 P. E. Macchia, Y. Takeuchi, T. Kawai, K. Cua, K. Gauthier, O. Chassande, H. Seo, Y. Hayashi, J. Samarut, Y. Murata, et al. Increased sensitivity to thyroid hormone in mice with complete deficiency of thyroid hormone receptor alpha PNAS, December 14, 2000; (2000) 11306998. [Abstract] [Full Text]
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 G. R. Williams Cloning and Characterization of Two Novel Thyroid Hormone Receptor beta Isoforms Mol. Cell. Biol., November 15, 2000; 20(22): 8329 - 8342. [Abstract] [Full Text]
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 M. L. Hastings, H. A. Ingle, M. A. Lazar, and S. H. Munroe Post-transcriptional Regulation of Thyroid Hormone Receptor Expression by cis-Acting Sequences and a Naturally Occurring Antisense RNA J. Biol. Chem., April 6, 2000; 275(15): 11507 - 11513. [Abstract] [Full Text] [PDF]
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P.-Y. Chien, M. Ito, Y. Park, T. Tagami, B. D. Gehm, and J. L. Jameson A Fusion Protein of the Estrogen Receptor (ER) and Nuclear Receptor Corepressor (NCoR) Strongly Inhibits Estrogen-Dependent Responses in Breast Cancer Cells Mol. Endocrinol., December 1, 1999; 13(12): 2122 - 2136. [Abstract] [Full Text]
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C. M. de Arrieta, B. Morte, A. Coloma, and J. Bernal The Human RC3 Gene Homolog, NRGN Contains a Thyroid Hormone-Responsive Element Located in the First Intron Endocrinology, January 1, 1999; 140(1): 335 - 343. [Abstract] [Full Text]
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P. E. Macchia, Y. Takeuchi, T. Kawai, K. Cua, K. Gauthier, O. Chassande, H. Seo, Y. Hayashi, J. Samarut, Y. Murata, et al. Increased sensitivity to thyroid hormone in mice with complete deficiency of thyroid hormone receptor alpha PNAS, January 2, 2001; 98(1): 349 - 354. [Abstract] [Full Text] [PDF]
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