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Department of Pharmacological and Physiological Science (H. M., C. M. B., P. N. M.), Saint Louis University Health Science Center, St. Louis, Missouri 63104, Genetics Unit, Shriners Hospital (R. S.), Montreal, Quebec H3G 1A6, Canada
Address correspondence to: Paul N. MacDonald, Ph.D., Saint Louis University Health Science Center, Department of Pharmacological and Physiological Science, 1402 South Grand Boulevard, St. Louis, Missouri 63104. Reprints are not available.
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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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,25-dihydroxyvitamin
D3 (1,25-(OH)2D3) (3, 4, 5). VDR and
other nuclear receptors display a modular structure, with several
regions (A/B, C, D, and E) exhibiting different degrees of evolutionary
conservation (2, 6). The N-terminal A/B region is the most divergent
module in these receptors, and an autonomous activation function,
designated AF-1, is present in the A/B region, which activates
transcription constitutively in the absence of the ligand binding
domain (LBD) (7, 8). The VDR is atypical in this regard since the A/B
region of VDR consists of only 20 amino acids, and deletion of these
residues does not affect VDR function (9). The highly conserved C
domain contains two zinc modules responsible for DNA binding and
sequence-specific recognition of vitamin D-responsive elements or
VDREs. The D region, or hinge domain, is located between the
DNA-binding domain (DBD) and the LBD. The hinge domain is hypothesized
to impart flexibility or a high degree of rotational freedom that
facilitates receptor binding to a variety of response elements (6). The
D region is also implicated in nuclear localization of receptors and in
transactivation (2). Finally, region E is responsible for selective
binding of the individual ligands with high affinity and selectivity.
Moreover, this C-terminal domain contains a dimerization interface and
a ligand-dependent transcriptional activation domain designated AF-2
(8, 10, 11, 12, 13). The mechanism through which the nuclear receptor-DNA complex regulates the transcriptional process is largely unknown. Recent data suggest that protein-protein contacts between the receptor and the basal transcriptional machinery are important for ligand-mediated transactivation or repression. Nuclear receptors directly contact several general transcription factors (GTFs) in the preinitiation complex (PIC), including TATA-binding protein (TBP) (14, 15), TBP-associated factors (TAFs) (16, 17), and transcription factor IIB (TFIIB) (18, 19, 20, 21). The interaction of receptors with these GTFs is thought to either recruit these limiting factors to PIC assembly or to stabilize the PIC itself (2). However, other factors in addition to the GTFs are required. This is based on the observation that one nuclear receptor interferes with another receptor’s transcriptional activation pathway without affecting basal transcription or the transcription of other promoters (22, 23, 24). Thus, while the interaction between nuclear receptors and the GTFs may be necessary, it is not sufficient for nuclear receptor-mediated transcription. Another class of factors that contact the nuclear receptors are needed, and these are collectively termed coactivators (review in 25 . Recently described coactivators, including steroid hormone receptor coactivator-1 (SRC-1) (26), estrogen receptor-associated protein (ERAP 160) (27), and receptor interacting protein (RIP140) (28), interact in a ligand-dependent manner with several members of the nuclear receptor superfamily to enhance ligand-induced transactivation. In contrast, several corepressors, such as nuclear receptor corepressor (N-CoR) and silencing mediator for retinoic acid receptors (RARs) and thyroid hormone receptors (SMRT), interact with unliganded receptors to inhibit basal transcription of the associated promoter (6, 25, 29, 30). Interestingly, the LBD (AF-2 domain) of the nuclear receptor is required both for the interaction with the majority of coactivators and for the dissociation of corepressor proteins, suggesting a mechanistic link between transcriptional suppression and activation (6, 30).
The AF-2 activating domain has been characterized in the C-terminal
part of region E of the RAR, retinoid X receptor (RXR), thyroid hormone
receptor (TR), and estrogen receptor (ER), and this region corresponds
to an amphipathic -helix motif whose main features are conserved
between all known transcriptionally active members of the nuclear
receptor superfamily (10, 12, 13). In most instances, the AF-2 motif is
transcriptionally silent in the absence of ligand, and ligand binding
activates its enhancer potential (10, 12, 13). In this paper, we
demonstrate that the conserved AF-2 motif of VDR is required both for
1,25-(OH)2D3-dependent transactivation and for
1,25-(OH)2D3-dependent interactions between VDR
and several putative coactivators including SRC-1 and RIP140. Indeed,
the minimal AF-2 domain of VDR was sufficient to mediate
transactivation as well as to mediate interactions between VDR and
SRC-1 or RIP140. Finally, we present evidence for a ligand-dependent
intramolecular interaction of the AF-2 helix with the VDR LBD. These
data support the hypothesis that the ligand promotes the folding of the
AF-2 domain to create a transactivation surface for coactivator
interaction and subsequent transactivation.
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RESULTS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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, the
C-terminal region of VDR examined in this study contained heptad 9,
which is an important region of VDR for dimerization with RXR (31), and
the AF-2 motif, which is highly conserved throughout the nuclear
receptor superfamily (10, 12, 13). A series of point mutations were
introduced into this C-terminal region of VDR to test the effects of
the mutations on vitamin D-mediated transactivation, ligand binding,
RXR heterodimerization, and VDRE interaction. Transient transfection
assays in COS-7 cells demonstrated that wild type VDR showed a 60-fold
induction of reporter gene expression in the presence of
10-8 M 1,25-(OH)2D3,
whereas the C-terminal deletion mutants [VDR(1–386) and
VDR(1–403)], which lacked the conserved AF-2 motif, were
transcriptionally inactive (Fig. 2A).
Introducing more subtle mutations into the AF-2 domain itself also
abolished VDR-mediated transactivation. The glutamic acid residue at
position 420 was changed to glutamine (E420Q) and the leucine residue
at position 417 was changed to serine (L417S), and both mutants lost
the ability to activate transcription. However, mutation of the
glutamic acid located downstream of the AF-2 core motif (E425Q) did not
significantly affect VDR-mediated transactivation compared with wild
type VDR. Similar results were obtained using another reporter
construct (VDRE4-TK-GH) and other cell lines (Hela cells,
ROS17/2.8 cells) (data not shown).
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). In contrast, the VDR(1–386)mutant displayed no
detectable ligand binding, and the apparent dissociation constant
(Kd) for the VDR(1–403) mutant was approximately 10-fold
higher than wild type VDR. However, as demonstrated by Whitfield
et al. (32), it is possible that subtle changes in ligand
binding may not be apparent in this in vitro binding assay.
Therefore, we examined whether high concentrations of ligand could
rescue the impairment in transactivation that was observed in the L417S
and E420Q mutants. While wild type VDR was maximally activated at
10-10 M 1,25-(OH)2D3,
the L417S and the E420Q VDR mutants were completely inactive even when
cells were treated with 10,000-fold higher ligand concentrations
(10-6 M) (Fig. 2B
). Thus, the absence of
transactivation in the L417S and E420Q mutants was not due to modest
alterations in ligand binding in vivo or in
vitro.
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).
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). Based on previously published data
(31) and on our two-hybrid results (Fig. 3), this is likely due to
disrupting the ability of VDR to heterodimerize with RXR and subsequent
weaker binding of the heterodimer to the VDRE. Importantly, the L417S
and E420Q mutants retained the ability to heterodimerize with RXR and
bind to the VDRE (lane 6 and 7) compared with wild type VDR (lane 1).
Western analysis showed that all VDR proteins were expressed to similar
levels in each of these extracts (Fig. 4B).
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). The
ligand-dependent transactivation by this heterologous construct was
mediated through the AF-2 domain since the AF-2 deletion mutant
[gal4-VDR(93–403)] and the AF-2 point mutants [gal4-VDR(L417S and
E420Q)] were inactive in the presence or absence of
1,25-(OH)2D3. N-Terminal deletions
[gal4-VDR(281–427, 374–427, and 387–427)] that eliminated ligand
binding were transcriptionally inactive in both the presence and
absence of 1,25-(OH)2D3 ligand. However, a
fusion protein consisting of the last 20 amino acids of VDR linked to
the gal4 DBD [gal4-VDR(408–427)] showed autonomous transactivation
activity that was unaffected by ligand. The level of reporter gene
expression with this minimal AF-2 domain fusion was approximately 40%
of the activity of the full-length LBD. To examine whether the
ligand-independent transactivation by this minimal AF-2 domain has an
amino acid requirement similar to that of ligand-dependent
transactivation, three-point mutations were introduced into the
gal4-VDR(408–427) construct (Fig. 5B). The L417S and the E420Q mutants
abolished the autonomous transactivation by the minimal AF-2 domain,
and E425Q mutation expressed an activity that was comparable to the
wild type AF-2 motif (Fig. 5B).
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To test whether the conserved AF-2 motif mediated the ligand-dependent
interaction between VDR and these putative coactivators, the VDR AF-2
mutants were examined in the two-hybrid interaction assay. Deletion of
the AF-2 motif [VDR(93–403)] resulted in no or weak interaction of
this mutant with the cofactors tested here (Fig. 6). Point mutations within the AF-2 core
(L417S and E420Q) also disrupted the interaction of VDR with mSUG1,
mSRC-1, and mRIP140 whereas mutations flanking the core had little
effect (K386Q, R391Q, and E425Q). It is important to note that most of
the AF-2 mutants still retained strong interactions with both RXR
and TFIIB (Fig. 3). Interestingly, the minimal AF-2 domain (residues
408–427), which demonstrated ligand-independent, autonomous
transactivation (Fig. 5A), also showed significant interactions with
all of the cofactors tested here. As illustrated in Fig. 7, AS1-VDR(408–427) demonstrated
significant interactions with mSRC-1 and mRIP140 while
pAS1-VDR(281–427), which had no autonomous transactivation activity
(Fig. 5), also did not interact with these putative coactivators in
this system. The introduction of two AF-2 point mutations into pAS1-VDR
(408–427) abolished the interaction with all cofactors, while the
mutation located downstream of the core AF-2 motif (E425Q) retained the
interactions. Interestingly, none of these minimal AF-2 fusions
interacted with RXR (Fig. 7) or with the pAD-Gal4 parent expression
vector (data not shown). Thus, ß-galactosidase activity determined in
these studies is a reflection of protein-protein interaction and is not
due to reporter gene expression driven by autonomous activation by the
AS-1-VDR(408–427) construct alone. In fact, these data demonstrate
that while the gal4-VDR(408–427) is an autonomous activator in
mammalian cells, it does not express detectable constitutive
transactivation in this yeast system.
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, the minimal AF-2 domain showed weak,
but significant, interactions with VDR(93–403) in the presence of
1,25-(OH)2D3. This interaction was markedly
reduced in the absence of ligand and was also not apparent using the
AS1-VDR(93–386) bait or the pAS1 parent expression vector.
Interestingly, introducing the E420Q or E425Q mutations into the
minimal AF-2 domain did not affect its interaction with VDR(93–403),
while the L417S mutant disrupted this interaction (Fig. 8B).
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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-helical region
encompassing heptad 9 (helix 11) as the central dimerization interface
in RXR and strongly implicated similar roles in structurally related
receptors (11). A second important domain in the C terminus of VDR is
the AF-2 motif, which functions as a ligand-dependent transactivation
domain. Mutation of conserved residues in RARs and TRs ablate
hormone-induced transactivation, implicating a predominant role of the
AF-2 domain in nuclear receptor-signaling pathways (10, 13). Although
the precise mechanisms involved in the AF-2 transactivation function
are not well understood, recent data indicate that this -helical
domain functions as an interaction surface for transcriptional
coactivator proteins that are putatively involved in nuclear
receptor-mediated transcription (6, 25). A detailed functional analysis
of the VDR AF-2 domain and the role of the
1,25-(OH)2D3 ligand in the activity of this
domain have been lacking. In this paper, we demonstrate the requirement
of an intact AF-2 core domain for
1,25-(OH)2D3-activated transcription.
Furthermore, we show that the AF-2 domain alone is sufficient to
mediate transactivation in a heterologous system and that it is also
sufficient to mediate interaction with several putative transcriptional
coactivator or adapter proteins.
Nakajima et al. (31) demonstrated that deletion of the VDR
AF-2 domain abolished VDR-mediated transactivation without compromising
heterodimerization of VDR with RXR and subsequent binding of
the VDR-RXR heterodimer to the VDRE. These data indicated a
selective role of the VDR AF-2 domain in
1,25-(OH)2D3-activated transcription. However,
1,25-(OH)2D3 binding to the VDR(1–403) mutant
was reduced by an order of magnitude compared with wild type VDR,
suggesting an additional role for the AF-2 domain in high- affinity
ligand binding (31). Similar results were obtained with VDR(1–403) in
the transactivation, two-hybrid interaction, and ligand-binding assays
in the present study (
Figs. 2–4 and Table 1). Indeed, the crystal
structures of liganded RAR and TRs show that the AF-2 motif is packed
onto the body of the receptor with a portion of it forming part of the
ligand-binding pocket (37, 40). This dual role of the AF-2 domain in
both transactivation and in high-affinity ligand binding complicates
the functional analysis of this domain in VDR-mediated transactivation.
However, in the present study, we defined point mutations within the
VDR AF-2 core motif (Fig. 1) that effectively discriminated between
transactivation and ligand-binding effects. While the VDR(E420Q) and
the VDR(L417S) mutants bound 1,25-(OH)2D3 with
equilibrium binding constants similar to wild type VDR (Table 1), both
point mutants were transcriptionally silent. Furthermore,
transactivation was not evident when the mutant receptors were
incubated with ligand concentrations that were 10,000-fold greater that
the apparent Kds (Fig. 2B). Altering a glutamic acid
residue that is adjacent to the conserved region (E425) did not
significantly affect transactivation. Consequently, these data
highlight the central importance of the charged and hydrophobic
residues within the AF-2 core motif in VDR-activated transcription.
Fusing the minimal AF-2 domain of VDR (residues 408–427) to a
heterologous DBD [Gal4(1–147)] produced a hybrid protein that
expressed significant transactivation potential in mammalian cells
(Fig. 5). These data are consistent with previous findings that similar
regions in TR, RAR, and RXR also function as autonomous transactivation
domains (10, 12, 13). Introducing the E420Q and L417S mutations into
this hybrid construct abolished transactivation by the minimal VDR AF-2
motif. Thus, E420 and L417 are essential for ligand-activated AF-2
activity in the intact receptor and for autonomous transactivation
mediated by the minimal AF-2 domain. Interestingly, Gal4-VDR hybrids
that expressed additional N-terminal sequences along with the minimal
AF-2 domain [i.e. VDR(383–427), VDR(373–427), and
VDR(281–427)] were transcriptionally silent in this assay. Perhaps
additional N-terminal sequence adjacent to the AF-2 core motif may mask
the AF-2 domain and inhibit its transactivation potential.
Alternatively, additional factors such as corepressor proteins may
interact with the VDR constructs containing this additional N-terminal
sequence that may inhibit or suppress AF-2 activity (29, 30).
Regardless, the chimera containing the full-length, intact LBD
[VDR(93–427)] was inactive in the absence of ligand, but it
expressed substantial transactivating activity in the presence of
10-8 M 1,25-(OH)2D3.
These data indicate that the AF-2 domain, while active on its own, is
not in the appropriate orientation or conformation for efficient
participation in the transactivation process in the intact receptor in
the absence of ligand. However, in the context of the intact receptor,
binding of ligand may alter the conformation of the AF-2 to promote
transactivation.
Importantly, we demonstrate that the minimal AF-2 domain of VDR interacts with an AF-2 deletion mutant of VDR [VDR(93–403)] in a ligand-dependent manner. We interpret this trans interaction between the isolated AF-2 domain and the remainder of the VDR LBD as a ligand-induced intramolecular folding of the AF-2 domain. Whereas the AF-2 mutation (E420Q) did not affect this ligand-dependent intramolecular contact, the L417S mutation severely impaired AF-2 interaction with the VDR LBD. These data imply that these two residues may, in fact, play distinct roles in the transactivation process. The hydrophobic residues (e.g. L417) may be involved in forming the hydrophobic core of the ligand-binding pocket and may be required for 1,25-(OH)2D3-dependent intramolecular folding of the AF-2 domain. In contrast, the charged residues (e.g. E420) may not be involved in intramolecular folding of the AF-2 domain, but instead this may be surface exposed and required for coactivator interaction. These observations are consistent with the putative model of ligand-induced conformational changes in the AF-2 domain based on the crystal structures of liganded RAR compared with unliganded RXR (11, 37). Interestingly, the minimal AF-2 domain [gal4-VDR(408–427)] expresses only 40% of the transcriptional activity and coactivator interaction observed with the full-length LBD in the presence of 1,25-(OH)2D3. This observation suggests that additional residues outside the AF-2 domain contribute to the transactivation surface. Additional studies are required to refine various aspects of this model and identify other residues that comprise the transactivation surface. Strong candidates may reside within the two activation domains identified in the VDR LBD in a yeast-based system (41).
Our ongoing studies to identify putative transcriptional adaptor proteins that interact with the VDR led to the isolation of several VDR-interactive clones from a murine osteoblast cDNA library in the yeast two-hybrid system. Sequence analysis revealed that three of the cDNA clones encoded putative coactivators implicated in nuclear receptor-mediated transcription including SRC-1 (26), RIP140 (28), and SUG1 (34). Importantly, these putative coactivators interacted with the VDR in a 1,25-(OH)2D3-dependent manner with the AF-2 domain of the VDR playing an essential role in this interaction. This is best exemplified in the observation that mutations in the AF-2 core motif disrupt interactions between VDR and SRC-1 or RIP140. These same mutations that abolish interaction with the coactivators also abolish transactivation. Moreover, the VDR AF-2 domain alone was sufficient to mediate interaction with these coactivators and to mediate autonomous transactivation. Although a direct examination of the effects of these coactivators on VDR-mediated transcription needs to be addressed, the strong correlation between coactivator interaction and transactivation observed in these studies supports a role for these putative coactivators in the mechanism of 1,25-(OH)2D3-activated transcription mediated through the VDR AF-2 domain.
In summary, we have analyzed the functional role of the extreme C-terminal region of VDR. Our data illustrate the distinct roles of heptad 9 (helix 11) in VDR dimerization with RXR as well as the central role that the conserved AF-2 motif plays in ligand-dependent coactivator interaction and transactivation. Importantly, these data support structural studies in which ligand binding induces a dramatic conformational change in the AF-2 domain mediated through an intramolecular folding of the AF-2 domain that creates a transcriptional surface for coactivator binding.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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COS-7 cells were cotransfected with reporter gene constructs (VDRE4-TATA-GH or Gal45-TATA-GH) and with receptor expression vectors (pSG5-VDR or pSG5-gal4-VDR). In all transfections, the amount of total DNA was kept constant at 10 µg by adding pTZ18U (U.S. Biochemical, Cleveland, OH) as a carrier plasmid. The cells were transfected by standard calcium phosphate coprecipitation procedures as described previously (43). Transfected cells were treated with the indicated concentrations of 1,25-(OH)2D3 or ethanol vehicle for 24 h, and the amount of secreted GH was determined with a RIA kit (Nichols Institute, San Juan Capistrano, CA).
Ligand-Binding Assay
COS-7 cell lysates expressing wild type or mutant human VDRs
were prepared as described previously (32). The lysates were incubated
with five different concentrations of
1,25-(OH)2-[3H]D3 (18 Ci/mmol)
overnight at 4 C in the presence or absence of a 400-fold molar excess
of unlabeled 1,25-(OH)2D3. Bound and free
ligand were separated with dextran-coated charcoal and analyzed by
Scatchard plots to determine the dissociation constant.
Gel Mobility Shift Analysis
The VDRE oligomer corresponding to the rat osteocalcin VDRE was
described previously (46). The VDRE oligomer was labeled to high
specific activity by a fill-in reaction with Klenow fragment of DNA
polymerase I and [-32P]dCTP (3000 Ci/nmol). Ten
micrograms of the lysates containing wild type or mutant human VDRs
were incubated with 32P-labeled VDRE probe for 30 min at 22
C in 10 mM Tris-HCl, pH 7.6, 100 mM KCl, 1.0
mM dithiothreitol, 15% glycerol, 0.1 µg/ml BSA, and 50
µg/ml poly(deoxyinosinic-deoxycytidylic)acid. Unbound probe and
protein-DNA complexes were separated by nondenaturing electrophoresis
on a 4% polyacrylamide gel in 0.25xTris-borate-EDTA. Gels were dried
and exposed for autoradiography.
Preparation of Two-Hybrid Expression Vectors and cDNA Library
Screening
All two-hybrid plasmids constructs used the pAS1 (47) and the
pGAD.GH (48) or pAD-GAL4 (Stratagene, La Jolla, CA) yeast expression
vectors. AS1-VDR constructs, containing the full-length and deletion
mutants of VDR [(93–427), (93–386), (281–427)], were described
previously (21). Other deletions [(93–403), (387–427), (408–427)]
and point mutations (K386Q, R391Q, L417S, E420Q, E425Q) of VDR were
also subcloned into the pAS1 or the pGAD.GH vector for examination in
the two-hybrid assay. The MC3T3-E1 cell cDNA library was prepared in
the pAD-GAL4 vector. For cDNA library screening, the library was
cotransformed with pAS1-VDR(93–427) into the yeast strain Hf7c, which
was made competent with lithium acetate (49). Transformants were plated
on media lacking leucine, tryptophan, and histidine (SC-leu-trp-his)
and containing 10-8 M
1,25-(OH)2D3 and 10 mM
3-amino-1,2,4-triazole. Histidine-positive colonies were assayed for
ß-galactosidase expression using a colony lift filter assay (47).
ß-Galactosidase Assays
The pAD-GAL4-mSUG1, -SRC-1, -RIP140, -RXR, and the
pGAD.GH-TFIIB, -RXR, -VDR were cotransformed with wild type and
mutant pAS1-VDR into the yeast strain Hf7c as described above.
Transformants were plated on media lacking leucine and tryptophan
(SC-leu-trp) and were grown for 4 days at 30 C to select for yeast that
had acquired both plasmids. Triplicate independent colonies from each
plate were grown overnight in 2 ml of SC-leu-trp with or without
10-8 M of
1,25-(OH)2D3. Cells were harvested and assayed
for ß-galactosidase activity as described (50).
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Received for publication April 21, 1997. Revision received June 5, 1997. Accepted for publication June 9, 1997.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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. Nature 375:377–382[CrossRef][Medline]
ligand-binding domain
bound to all-trans retinoic acid. Nature 378:681–689[CrossRef][Medline]
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C. Zhang, D. R. Dowd, A. Staal, C. Gu, J. B. Lian, A. J. van Wijnen, G. S. Stein, and P. N. MacDonald Nuclear Coactivator-62 kDa/Ski-interacting Protein Is a Nuclear Matrix-associated Coactivator That May Couple Vitamin D Receptor-mediated Transcription and RNA Splicing J. Biol. Chem., September 12, 2003; 278(37): 35325 - 35336. [Abstract] [Full Text] [PDF]
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A. L. M. Sutton and P. N. MacDonald Vitamin D: More Than a "Bone-a-Fide" Hormone Mol. Endocrinol., May 1, 2003; 17(5): 777 - 791. [Abstract] [Full Text] [PDF]
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J. B. Barry, G. M. Leong, W. B. Church, L. L. Issa, J. A. Eisman, and E. M. Gardiner Interactions of SKIP/NCoA-62, TFIIB, and Retinoid X Receptor with Vitamin D Receptor Helix H10 Residues J. Biol. Chem., February 28, 2003; 278(10): 8224 - 8228. [Abstract] [Full Text] [PDF]
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Y. Chen, A. Kerimo, S. Khan, and L.-N. Wei Real-Time Analysis of Molecular Interaction of Retinoid Receptors and Receptor-Interacting Protein 140 (RIP140) Mol. Endocrinol., November 1, 2002; 16(11): 2528 - 2537. [Abstract] [Full Text] [PDF]
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P. J. Malloy, R. Xu, L. Peng, P. A. Clark, and D. Feldman A Novel Mutation in Helix 12 of the Vitamin D Receptor Impairs Coactivator Interaction and Causes Hereditary 1,25-Dihydroxyvitamin D-Resistant Rickets without Alopecia Mol. Endocrinol., November 1, 2002; 16(11): 2538 - 2546. [Abstract] [Full Text] [PDF]
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F. Gizard, B. Lavallee, F. DeWitte, E. Teissier, B. Staels, and D. W. Hum The Transcriptional Regulating Protein of 132 kDa (TReP-132) Enhances P450scc Gene Transcription through Interaction with Steroidogenic Factor-1 in Human Adrenal Cells J. Biol. Chem., October 11, 2002; 277(42): 39144 - 39155. [Abstract] [Full Text] [PDF]
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 H. Masuyama, H. Inoshita, Y. Hiramatsu, and T. Kudo Ligands Have Various Potential Effects on the Degradation of Pregnane X Receptor by Proteasome Endocrinology, January 1, 2002; 143(1): 55 - 61. [Abstract] [Full Text] [PDF]
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T. Ishizuka, T. Satoh, T. Monden, N. Shibusawa, T. Hashida, M. Yamada, and M. Mori Human Immunodeficiency Virus Type 1 Tat Binding Protein-1 Is a Transcriptional Coactivator Specific for TR Mol. Endocrinol., August 1, 2001; 15(8): 1329 - 1343. [Abstract] [Full Text] [PDF]
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M. Raval-Pandya, P. Dhawan, F. Barletta, and S. Christakos YY1 Represses Vitamin D Receptor-Mediated 25-Hydroxyvitamin D3 24-Hydroxylase Transcription: Relief of Repression by CREB-Binding Protein Mol. Endocrinol., June 1, 2001; 15(6): 1035 - 1046. [Abstract] [Full Text] [PDF]
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L. L. Issa, G. M. Leong, J. B. Barry, R. L. Sutherland, and J. A. Eisman Glucocorticoid Receptor-Interacting Protein-1 and Receptor-Associated Coactivator-3 Differentially Interact with the Vitamin D Receptor (VDR) and Regulate VDR-Retinoid X Receptor Transcriptional Cross-Talk Endocrinology, April 1, 2001; 142(4): 1606 - 1615. [Abstract] [Full Text]
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C. Hellal-Levy, J. Fagart, A. Souque, J.-M. Wurtz, D. Moras, and M.-E. Rafestin-Oblin Crucial Role of the H11-H12 Loop in Stabilizing the Active Conformation of the Human Mineralocorticoid Receptor Mol. Endocrinol., August 1, 2000; 14(8): 1210 - 1221. [Abstract] [Full Text]
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S. Chen, J. Cui, K. Nakamura, R. C. J. Ribeiro, B. L. West, and D. G. Gardner Coactivator-Vitamin D Receptor Interactions Mediate Inhibition of the Atrial Natriuretic Peptide Promoter J. Biol. Chem., May 12, 2000; 275(20): 15039 - 15048. [Abstract] [Full Text] [PDF]
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P. W. Jurutka, L. S. Remus, G. K. Whitfield, P. D. Thompson, J.-C. Hsieh, H. Zitzer, P. Tavakkoli, M. A. Galligan, H. T. L. Dang, C. A. Haussler, et al. The Polymorphic N Terminus in Human Vitamin D Receptor Isoforms Influences Transcriptional Activity by Modulating Interaction with Transcription Factor IIB Mol. Endocrinol., March 1, 2000; 14(3): 401 - 420. [Abstract] [Full Text]
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H. Masuyama, Y. Hiramatsu, M. Kunitomi, T. Kudo, and P. N. MacDonald Endocrine Disrupting Chemicals, Phthalic Acid and Nonylphenol, Activate Pregnane X Receptor-Mediated Transcription Mol. Endocrinol., March 1, 2000; 14(3): 421 - 428. [Abstract] [Full Text]
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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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K. Ozono, M. Saito, D. Miura, T. Michigami, S. Nakajima, and S. Ishizuka Analysis of the Molecular Mechanism for the Antagonistic Action of a Novel 1alpha ,25-Dihydroxyvitamin D3 Analogue toward Vitamin D Receptor Function J. Biol. Chem., November 5, 1999; 274(45): 32376 - 32381. [Abstract] [Full Text] [PDF]
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 F. M. Sladek, M. D. Ruse Jr., L. Nepomuceno, S.-M. Huang, and M. R. Stallcup Modulation of Transcriptional Activation and Coactivator Interaction by a Splicing Variation in the F Domain of Nuclear Receptor Hepatocyte Nuclear Factor 4alpha 1 Mol. Cell. Biol., October 1, 1999; 19(10): 6509 - 6522. [Abstract] [Full Text] [PDF]
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A. Racz and J. Barsony Hormone-dependent Translocation of Vitamin D Receptors Is Linked to Transactivation J. Biol. Chem., July 2, 1999; 274(27): 19352 - 19360. [Abstract] [Full Text] [PDF]
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F. F. Wiebel, K. R. Steffensen, E. Treuter, D. Feltkamp, and J.-A. Gustafsson Ligand-Independent Coregulator Recruitment by the Triply Activatable OR1/Retinoid X Receptor-{alpha} Nuclear Receptor Heterodimer Mol. Endocrinol., July 1, 1999; 13(7): 1105 - 1118. [Abstract] [Full Text]
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A. I. Castillo, A. M. Jimenez-Lara, R. M. Tolon, and A. Aranda Synergistic Activation of the Prolactin Promoter by Vitamin D Receptor and GHF-1: Role of the Coactivators, CREB-Binding Protein and Steroid Hormone Receptor Coactivator-1 (SRC-1) Mol. Endocrinol., July 1, 1999; 13(7): 1141 - 1154. [Abstract] [Full Text]
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Y.-F. Lee, W.-J. Young, W.-J. Lin, C.-R. Shyr, and C. Chang Differential Regulation of Direct Repeat 3 Vitamin D3 and Direct Repeat 4 Thyroid Hormone Signaling Pathways by the Human TR4 Orphan Receptor J. Biol. Chem., June 4, 1999; 274(23): 16198 - 16205. [Abstract] [Full Text] [PDF]
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A. M. Jiménez-Lara and A. Aranda Vitamin D Represses Retinoic Acid-Dependent Transactivation of the Retinoic Acid Receptor-{beta}2 Promoter: The AF-2 Domain of the Vitamin D Receptor Is Required for Transrepression Endocrinology, June 1, 1999; 140(6): 2898 - 2907. [Abstract] [Full Text]
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 A. M. JIMENEZ-LARA and A. ARANDA The vitamin D receptor binds in a transcriptionally inactive form and without a defined polarity on a retinoic acid response element FASEB J, June 1, 1999; 13(9): 1073 - 1081. [Abstract] [Full Text]
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M. Quack and C. Carlberg Selective Recognition of Vitamin D Receptor Conformations Mediates Promoter Selectivity of Vitamin D Analogs Mol. Pharmacol., June 1, 1999; 55(6): 1077 - 1087. [Abstract] [Full Text]
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D. M. Kraichely, J. J. Collins III, R. K. DeLisle, and P. N. MacDonald The Autonomous Transactivation Domain in Helix H3 of the Vitamin D Receptor Is Required For Transactivation and Coactivator Interaction J. Biol. Chem., May 14, 1999; 274(20): 14352 - 14358. [Abstract] [Full Text] [PDF]
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A. M. Jimenez-Lara and A. Aranda Lysine 246 of the Vitamin D Receptor Is Crucial for Ligand-dependent Interaction with Coactivators and Transcriptional Activity J. Biol. Chem., May 7, 1999; 274(19): 13503 - 13510. [Abstract] [Full Text] [PDF]
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P. J. Malloy, J. W. Pike, and D. Feldman The Vitamin D Receptor and the Syndrome of Hereditary 1,25-Dihydroxyvitamin D-Resistant Rickets Endocr. Rev., April 1, 1999; 20(2): 156 - 188. [Abstract] [Full Text]
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 Z. Nawaz, D. M. Lonard, A. P. Dennis, C. L. Smith, and B. W. O'Malley Proteasome-dependent degradation of the human estrogen receptor PNAS, March 2, 1999; 96(5): 1858 - 1862. [Abstract] [Full Text] [PDF]
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 J. Yanagisawa, Y. Yanagi, Y. Masuhiro, M. Suzawa, M. Watanabe, K. Kashiwagi, T. Toriyabe, M. Kawabata, K. Miyazono, and S. Kato Convergence of Transforming Growth Factor- and Vitamin D Signaling Pathways on SMAD Transcriptional Coactivators Science, February 26, 1999; 283(5406): 1317 - 1321. [Abstract] [Full Text]
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K.-I. Takeyama, Y. Masuhiro, H. Fuse, H. Endoh, A. Murayama, S. Kitanaka, M. Suzawa, J. Yanagisawa, and S. Kato Selective Interaction of Vitamin D Receptor with Transcriptional Coactivators by a Vitamin D Analog Mol. Cell. Biol., February 1, 1999; 19(2): 1049 - 1055. [Abstract] [Full Text] [PDF]
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C.-H. Lee, C. Chinpaisal, and L.-N. Wei Cloning and Characterization of Mouse RIP140, a Corepressor for Nuclear Orphan Receptor TR2 Mol. Cell. Biol., November 1, 1998; 18(11): 6745 - 6755. [Abstract] [Full Text]
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 B. D. Darimont, R. L. Wagner, J. W. Apriletti, M. R. Stallcup, P. J. Kushner, J. D. Baxter, R. J. Fletterick, and K. R. Yamamoto Structure and specificity of nuclear receptor-coactivator interactions Genes & Dev., November 1, 1998; 12(21): 3343 - 3356. [Abstract] [Full Text]
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 G. JONES, S. A. STRUGNELL, and H. F. DeLUCA Current Understanding of the Molecular Actions of Vitamin D Physiol Rev, October 1, 1998; 78(4): 1193 - 1231. [Abstract] [Full Text] [PDF]
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M. Raval-Pandya, L. P. Freedman, H. Li, and S. Christakos Thyroid Hormone Receptor Does Not Heterodimerize with the Vitamin D Receptor but Represses Vitamin D Receptor-Mediated Transactivation Mol. Endocrinol., September 1, 1998; 12(9): 1367 - 1379. [Abstract] [Full Text]
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T. A. Baudino, D. M. Kraichely, S. C. Jefcoat Jr., S. K. Winchester, N. C. Partridge, and P. N. MacDonald Isolation and Characterization of a Novel Coactivator Protein, NCoA-62, Involved in Vitamin D-mediated Transcription J. Biol. Chem., June 26, 1998; 273(26): 16434 - 16441. [Abstract] [Full Text] [PDF]
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C. Rachez, Z. Suldan, J. Ward, C.-P. B. Chang, D. Burakov, H. Erdjument-Bromage, P. Tempst, and L. P. Freedman A novel protein complex that interacts with the vitamin D3 receptor in a ligand-dependent manner and enhances VDR transactivation in a cell-free system Genes & Dev., June 15, 1998; 12(12): 1787 - 1800. [Abstract] [Full Text]
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S. Peleg, C. Nguyen, B. T. Woodard, J.-K. Lee, and G. H. Posner Differential Use of Transcription Activation Function 2 Domain of the Vitamin D Receptor by 1,25-Dihydroxyvitamin D3 and Its A Ring-Modified Analogs Mol. Endocrinol., April 1, 1998; 12(4): 525 - 535. [Abstract] [Full Text]
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 K.R. YAMAMOTO, B.D. DARIMONT, R.L. WAGNER, and J.A. INIGUEZ-LLUHI Building Transcriptional Regulatory Complexes: Signals and Surfaces Cold Spring Harb Symp Quant Biol, January 1, 1998; 63(0): 587 - 598. [Abstract] [PDF]
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L.-N. Wei, X. Hu, D. Chandra, E. Seto, and M. Farooqui Receptor-interacting Protein 140 Directly Recruits Histone Deacetylases for Gene Silencing J. Biol. Chem., December 22, 2000; 275(52): 40782 - 40787. [Abstract] [Full Text] [PDF]
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C. Zhang, T. A. Baudino, D. R. Dowd, H. Tokumaru, W. Wang, and P. N. MacDonald Ternary Complexes and Cooperative Interplay between NCoA-62/Ski-interacting Protein and Steroid Receptor Coactivators in Vitamin D Receptor-mediated Transcription J. Biol. Chem., October 26, 2001; 276(44): 40614 - 40620. [Abstract] [Full Text] [PDF]
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