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Department of Cell Biology Baylor College of Medicine Houston, Texas 77030
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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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Transcripts for the nurr1 subfamily are constitutively expressed in a differentially restricted but partially overlapping temporal and spatial pattern (7, 8). Whereas nurr1 expression appears to be restricted to brain tissue in the developing and adult mouse, the constitutive expression of nur77 and NOR-1 is observed in some peripheral tissues in addition to brain (7, 14). Nur77 mRNA is present in several tissues including testis, ovary, and muscle (7) whereas low NOR-1 expression is detected in the thymus, kidney, and spleen (14). Further, unlike most nuclear receptors, these proteins are products of immediate early genes whose expression can be differentially induced in response to a variety of extracellular stimuli including growth factors (9, 10, 21), neurotransmitters (22, 23), and polypeptide hormones (24, 25).
Several lines of evidence indicate that the members of the nurr1
subfamily may play an important role in the coordinate neuroendocrine
regulation of the activity of the hypothalamic/pituitary/adrenal (HPA)
axis. This axis is regulated at the level of the hypothalamus by CRF,
which is synthesized in the hypothalamic paraventricular nucleus (PVN).
In response to stressful stimuli, CRF is released from the PVN and
transported to the anterior pituitary causing an increase in synthesis
of POMC. POMC is a precursor molecule of several neuropeptides
including ACTH, which is released from the pituitary and regulates the
synthesis of glucocorticoids from the adrenal cortex. To maintain
homeostasis, glucocorticoids inhibit CRF and POMC synthesis and
secretion at the level of the hypothalamus and anterior pituitary. It
has previously been shown that while nurr1 is constitutively expressed
in the PVN (8), nur77 mRNA is rapidly induced in this region by stress
(26) and interleukin-1ß (27), both important regulators of
hypothalamic CRF. Also, central administration of CRF to conscious rats
significantly increases the expression of nur77 within the PVN (28). We
have shown that nurr1 and nur77 are both expressed in the anterior
pituitary, the site of POMC synthesis (8). Further, nur77 and nurr1
transcripts are strongly induced by stress in the adrenal cortex (25).
The induction of nur77 in this region has been implicated in the
transcriptional induction of the steroidogenic enzyme
steroid-21
-hydroxylase (24), a rate-limiting enzyme in
glucocorticoid synthesis. However, recent reports reveal that nur77
null mutant mice display no abnormal functions of the HPA axis (29).
The absence of detectable phenotypic changes in the HPA axis has been
proposed to reflect a functional redundancy by nurr1 because levels of
this mRNA, after HPA axis stimulation, are compensatorily increased in
the adrenal gland of nur77 null mutant mice (29). Finally, our
laboratory recently identified specific DNA-binding sites for nurr1 and
nur77 in the proximal promoter region of the CRF and POMC genes that
may mediate nurr1 subfamily-dependent regulation of these genes in the
hypothalamus and pituitary, respectively (19).
The aim of this study was to examine the neuroendocrine regulation of the HPA axis by the nurr1 subfamily. We report here that, as predicted by our previous DNA-binding studies (19), nurr1 and nur77 interact specifically with the CRF (-352/-332) and POMC (-70/-47) promoter elements in electrophoretic mobility shift assays (EMSA). Cotransfection experiments in pituitary-derived cells show that nurr1 can increase the transcriptional activity of both promoters. Further, mutational analysis of the nurr1 consensus site within the POMC promoter results in loss of nurr1-stimulated expression. CRF functions through the secondary messenger cAMP to potently stimulate POMC gene transcription within pituitary cells. By increasing cAMP levels within a pituitary cell line, we observe a rapid and robust increase of nurr1 and nur77 mRNAs, suggesting CRF induction of POMC synthesis may be mediated through these transcription factors. Finally, examination of the nurr1 consensus sequence in the POMC promoter reveals that the element overlaps with a well characterized negative glucocorticoid receptor response element (nGRE). We provide evidence to indicate that glucocorticoid repression of the POMC gene may be mediated, at least in part, by glucocorticoid receptor (GR)-dependent inhibition of activation of the POMC gene by nurr1 subfamily members. Our results strongly support the conclusion that the nurr1 subfamily of nuclear receptors plays a coordinate role in neuroendocrine regulation of the activity of the HPA axis.
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RESULTS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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To test whether nurr1 and nur77 interact directly with the POMC
-70/-47 and CRF -352/-332 regions, we prepared 32P-
labeled oligonucleotides containing these regions and used EMSA to
examine their binding to nurr1 and nur77 translated in vitro
in the reticulolysate system. The results of these assays are shown in
Fig. 1
. Incubation with nurr1 resulted in a retarded
radiolabeled complex that was observed when either the POMC (panel A,
lane 2) or CRF (panel C, lane 2) promoter fragments were used. These
complexes were nurr1 dependent and were not observed in the absence of
nurr1 in the reticulolysate (lane 1, both panels). Furthermore, complex
formation on both promoters was specifically inhibited by increasing
concentrations of unlabeled homologous oligonucleotide (lanes 3–5) but
not by a heterologous oligonucleotide (lane 6), indicating that binding
to these DNA fragments was specific and competitive. Finally, mutation
of the GAAGGTCA motif to GAACATCA or
GTACGTCA within these sequences resulted in
loss of ability to competitively inhibit nurr1-dependent binding,
indicating that this sequence is essential for the nurr1 interaction
(lanes 7–9). Similar results were obtained when nur77 was used in EMSA
instead of nurr1 (panels B and D).
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, cotransfection of these target genes with nurr1
results in a 7- to 12-fold stimulation of the rat, human POMC, and oCRF
promoters over that observed when the target genes are cotransfected
with the parent expression vector lacking nurr1 (p91023B). To confirm
that the nurr1-dependent induction transcription is due to the presence
of the GAAGGTCA motif within the promoter, we introduced point
mutations within this element in the rPOMC promoter to
GAACATCA, which we have shown to result in loss of nurr1
binding in vitro (Fig. 1
), and we examined the regulation of
this promoter construct by nurr1. As shown in Fig. 2B, nurr1 induction
of the POMC promoter is lost when the mutated promoter construct (rPOMC
MT1) is used, indicating that a functional GAAGGTCA motif is essential
for transcriptional induction of the POMC promoter by nurr1. When nurr1
was replaced by nur77 in these assays, similar results were observed
(data not shown), indicating that both subfamily members can regulate
the expression of the CRF and POMC promoters and may function
redundantly to do so in a physiological context if coexpressed.
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, both nurr1 and nur77 transcripts are rapidly
induced by CRF within 15 min of treatment and are maximal at
approximately 30 min. Further, this induction slightly precedes the
previously reported time course of POMC transcription by CRF, which is
maximal by 30–60 min (35, 36).
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). The time course of this induction correlates with
the time course of CRF induction of nurr1 and nur77 in the isolated
pituitary cells. Further, we show that forskolin can significantly
stimulate the expression of the rPOMC-chloramphenicol acetyltransferase
(CAT) reporter gene when transfected into AtT20/D cells. Most
importantly, however, the induction of POMC-CAT by forskolin is reduced
when the nurr1 binding site is destroyed by point mutation of the
GAAGGTCA motif (rPOMC MT1), and the basal activity of the promoter is
also decreased. Finally, when the GAAGGTCA alone is placed in front of
a heterologous promoter [thymidine kinase (tk) (34)], this enhancer
element is sufficient to mediate induction of this promoter by
forskolin (Fig. 4). The results confirm that the nurr1-binding site
plays an important role in the induction of this promoter by cAMP
pathways and also contributes to the basal activity of the POMC
promoter in pituitary cells.
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). Mutation of the GAAGGTCA motif to
GAACATCA has been shown to convert the nGRE into a positive
enhancer element that mediates induction of the enhancer element by GR
(40) when placed upstream of a heterologous basal promoter. In
preliminary studies to test the hypothesis that the nurr1-binding site
is pivotal to both positive regulation by nurr1 and negative feedback
by GR, we confirm that forskolin regulation of the POMC promoter is
down-regulated by pretreatment with dexamethasone (36) and that
rPOMC-MT1, while not responding to forskolin or nurr1, is up-regulated
by dexamethasone (Fig. 5B). These data predicted that GR may inhibit
expression of POMC in the pituitary, at least in part, by either
directly or indirectly inhibiting binding of the nurr1 subfamily to the
GAAGGTCA motif. To directly test this predication, we carried out EMSA
on nuclear extracts to examine the DNA-binding properties of nurr1 in
forskolin- and dexamethasone-treated cells. The results are shown in
Fig. 5C. In unstimulated AtT20/D cells, two proteins, presumably nurr1
and nur77, bound to the rPOMC -70/-47 probe (lane 1). Stimulation of
the cells with 25 µM forskolin for 1 h resulted in
significant increased binding of both proteins to DNA (lane 4). Binding
was inhibited by 25x molar excess of homologous oligonucleotide (lanes
2 and 5) but not by the oligonucleotide containing a mutation of the
nurr1-binding site rPOMC -70/-47MT1 (lanes 3 and 6). The larger
protein complex was selectively blocked by nurr1-specific antiserum
(lane 8) (8). These results confirm that the cAMP-dependent increases
in nurr1 mRNA in these cells correlate with an increase in specific
binding of nurr1 protein to the POMC promoter sequence. Further, as
predicted by our transactivation results, pretreatment with
dexamethasone inhibited binding of both proteins to DNA and also
diminished the basal DNA-binding activity (lane 10). These results
confirm that the nurr1-binding site can play a pivotal role in both
basal and cAMP-mediated up-regulation of the POMC promoter and its
down-regulation by GRs.
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DISCUSSION |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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As predicted by the species conservation of the nurr1-binding site, we confirmed that transactivation of the POMC gene by nurr1 is conserved between rat and human species. Further, we showed that mutation of the nurr1-binding site within the POMC promoter results in loss of ability to bind nurr1 and inhibits nurr1-dependent activation of this promoter, confirming that the GAAGGTCA sequence motif is essential for nurr1-dependent induction of POMC expression. To determine whether nurr1 and/or nur77 are likely to mediate CRF- dependent induction of POMC expression in the anterior pituitary, we confirmed that the expression of both nurr1 and nur77 is rapidly induced by stimulation of isolated mouse pituitary cells with CRF. Further, we demonstrated that this induction can be mimicked in AtT20/D cells by activation of cAMP-dependent pathways by forskolin. Forskolin stimulation results in increased binding of endogenous nurr1 to DNA and a functional POMC-CAT transactivation response. These data indicate that cAMP may regulate the POMC promoter, at least in part, by increasing expression of the nurr1 subfamily. However, nur77 has also been shown to be phosphorylated by cAMP (25), and cAMP has also been shown to alter the transcriptional activity of nurr1 and nur77 (42). Thus, both covalent modification of existing pools of nur proteins and de novo synthesis are likely to contribute to cAMP-dependent induction of the POMC promoter.
The observation that forskolin induction of the rPOMC-CAT target gene is diminished by mutation of the nurr1-binding site illustrates the importance of this cis-acting sequence in mediating cAMP-dependent induction of POMC expression in the anterior pituitary cell line. While CRF is known to induce expression of POMC through a cAMP-dependent pathway, previous studies have not uncovered a recognizable cis-acting cAMP response element that may mediate this response (43). The location of cAMP-responsive sequences in the POMC promoter has therefore been controversial. Previous studies have indicated that sequences located upstream (-236/-133) of the nurr1-binding site are responsive to CRF when placed upstream of a heterologous promoter and may contribute to hormonal regulation of the endogenous gene (43). While our data support a major role for the nurr1-binding site located at -60/-70 in mediating cAMP responses in the context of the endogenous POMC promoter, the lack of complete inhibition of POMC induction by mutation of this sequence indicates that additional sequences outside of this region may also contribute to cAMP-mediated induction of expression of this gene.
The nurr1-binding site overlaps with a previously identified nGRE that has been shown to be important for GR-mediated repression of the POMC gene and is also important for basal expression of this promoter (31, 39, 40, 44). Consistent with the reported contribution of this region to basal promoter activity (44), we observed that mutation of the nurr1-binding site also results in decreased basal promoter activity. Two critical nucleotides within the nGRE are critical for both GR repression (40) and nurr1 transactivation. Mutation of these nucleotides, as we have done in our study (POMC-MT1), converted the nGRE into a positive GR response element when placed in front of a heterologous promoter (40). We have demonstrated that although this mutated sequence no longer responds to nurr1 and demonstrates diminished response to forskolin, the mutant target gene is induced by dexamethasone. These data support the conclusion that the nurr1-binding site plays an important role in negative regulation of the POMC gene by glucocorticoids as well as nurr1-mediated basal and cAMP-inducible expression of POMC. Further, we show that GR-mediated inhibition of the POMC gene is accompanied by an inhibition of nurr1 subfamily-dependent DNA binding to the GAAGGTCA response element, demonstrating functional antagonism between these two nuclear receptors. Thus, the nurr1 subfamily may play a pivotal role in regulation of neuroendocrine homeostasis at the pituitary level.
The data we have provided in the present study, together with the
demonstrated expression (8) and induction (26, 27, 28) of nurr1 subfamily
members in the hypothalamic PVN, and the demonstration by others (24)
that nur77 can mediate the regulation of expression of the
steroidogenic enzyme, steroid-21 -hydroxylase by the POMC processing
product, ACTH, indicate that members of the nurr1 subfamily may be
important coordinators of the activity of the HPA axis at all levels.
Despite these observations, however, recent analysis of HPA activity in
homozygous nur77 null mutant mice has detected no disturbance in this
neuroendocrine pathway (29). In fact, the only significant difference
between wild type and homozygous animals observed in this pathway was a
compensatory increase in the induction of nurr1 by stress in nur77 null
mutant animals that was not observed in the wild type mice (29). This
observation highlights the capacity for redundancy of function between
nurr1 subfamily members. Our analysis of the comparative developmental
expression of nurr1 and nur77 has indicated that nurr1 is selectively
expressed during embryonic development, particularly in the
diencephalic regions that give rise to the hypothalamus at a time that
coincides with the developmental organization of the HPA axis, whereas
nur77 is not expressed until the postnatal stage (O. Saucedo-Cardenas
and O. Conneely, manuscript in preparation). Given the ability of nurr1
to substitute functionally for nur77, it is not surprising that nur77
null mutant mice do not show any detectable aberrant phenotypes in the
HPA because nur77 expression does not begin until the postnatal stage
of development at a time when nurr1 is already expressed. Thus, nurr1
may play a selective role in the developmental organization and
activity of the HPA axis that is not substituted by nur77. Finally, the
ontogeny and impact, if any, of the third subfamily member, NOR-1, on
this pathway remain to be established. With the use of gene-targeting
strategies, null mutation of these genes in mice should provide
valuable insights into the selective and collective functions of these
proteins in vivo, including their essential role, if any, in
the neuroendocrine development and activity of the HPA axis.
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MATERIALS AND METHODS |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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CRF-1 genomic
clone (30). p-483POMC-CAT reporters were also generated by PCR using
rat and human genomic DNA. The PCR products were subcloned into
pBL3CAT, which lacks the minimal tk promoter (34). All PCR
products were sequenced by the dideoxy method (47). The M2G
(GAAGGTCA)2 tk-CAT reporter plasmid was made by ligating
double-stranded oligonucleotides, containing two inverted copies of the
response element oligonucleotide separated by 10 nucleotides, into the
BamHI site of pBL2CAT, upstream of the minimal
tk promoter (34).
In Vitro Transcription and Translation
In vitro transcription and translation was
accomplished with the TNT kit (Promega, Madison, WI) with the addition
of RNAsin (Promega). Nurr1 and nur77 were transcribed with
T7 RNA polymerase from pT7ß-6 recombinant
plasmid (45), a derivative of pGEM 2 in which the ß-globin insert of
pSP6 Hß 166 6 was inserted at the initiation codon to
create the sequence CCATGCCTCGACCATGG (48). The translation was carried
out in the presence of [35S]methionine and run on an
8.5% denaturing gel or cold methionine for use in the mobility shift
assay, according to the manufacturers directions; 1–2.5 µl of a
translation mixture was used in each gel shift-binding reaction.
EMSA
EMSA were performed with in vitro translated proteins
in a rabbit reticulocyte lysate system (TNT, Promega) or AtT20/D
nuclear extracts. Proteins were mixed with 100,000 cpm of
Klenow-labeled probes in the reaction buffer, 20 mM HEPES,
pH 7.9, 5 mM MgCl2, 20% glycerol, 100
mM KCl, 0.2 mM EDTA, 8% Ficoll, 600
mM KCl, 500 ng/µl poly(deoxyinosinic-deoxycytidylic)acid,
and 50 mM dithiothreitol (DTT). The reaction was incubated
for 20 min at room temperature and then electrophoresed through a 5.5%
nondenaturing polyacrylamide gel in 0.5x Tris-Borate-EDTA (TBE)
electrophoresis buffer. Nurr1-specific antiserum (8) was incubated with
nuclear extract for 15 min before the addition of probe. For
competition studies, the reaction was performed as described with the
indicated concentrations of unlabeled probe. The sequences of the
oligonucleotides studied are listed as follows: rPOMC -70/-47
5'-GATCT-70CAGGAAGGTCACGTCCAAGGCTCA-47 rPOMC -70/-47MT1
5'-GATCT-70CAGGAACATCACGTCCAAGGCTCA-47 oCRF -352/-332
5'-GA-352TCTTTCTGACCTTCCCTTTA-332 oCRF -352/-332MT1
5'-GA-352TCTTTCTGACGTACCCTTTA-332
Preparation of Nuclear Extracts
AtT20/D16V-F2 cells untreated or treated with 25
µM forskolin were washed with cold PBS, resuspended, and
incubated for 5 min in 0.25 ml buffer A (10 mM HEPES-KOH pH
7.9, 1.5 mM MgCL2, 10 mM KCL, 0.5
mM DTT, 0.1 mM EGTA, 0.5 mM
phenylmethylsulfonylfluroide, and 2 µg each of the protease
inhibitors antipain, pepstatin A, and aprotinin per ml). Then, 1.25
µl of 10% Nonidet P-40 were added, and the cells were incubated for
2 min on ice. The cells were centrifuged at low speed (1,7000 rpm), and
the supernatant was removed (cytosolic fraction). To the pellet, 0.125
ml of buffer B (0.4 M NaCL, 10 mM HEPES-KOH, pH
7.9, 1.5 mM MgCl2, 0.1 mM EGTA, 0.5
mM DTT, 5% glycerol, and 0.5 mM
phenylmethylsulfonylfluoride) was added. The mixture was vortexed at 4
C and left on ice for 5 min. The extracts were then centrifuged, and
the supernatant was dialyzed against 50 volumes of buffer C (20
mM HEPES-KOH, pH 7.9, 75 mM NaCl, 0.1
mM EDTA, 0.5 mM DTT, 20% glycerol, and 0.5
mM phenylmethylsulfonylfluoride) for 4 h at 4 C with
one change of buffer C. After 4 h, the materials that precipitated
during dialysis were removed by centrifugation, and the supernatant was
aliquoted, flash frozen in liquid N2, and stored at
-80°C until further use. The protein concentration was estimated
with the Bradford protein assay kit (Bio-Rad, Richmond, CA). One
microgram of protein was used in the EMSA.
Cell Culture and Transfection
AtT20/D16V-F2 were grown in DMEM supplemented with 10% FBS,
penicillin at 100 µg/ml, and streptomycin at 100 µg/ml in a
humidified atmosphere of 5% CO2 and 95% air. Twenty four
hours before transfection, 2 x 105 cells were plated
in 3-cm dishes in DMEM supplemented with 10% FBS and were allowed to
attach. The cells were then washed with Hanks Balanced Salt Solution
(HBSS) lacking calcium and magnesium and incubated in DMEM supplemented
with 10% horse serum for AtT20/D cells. Cells treated with forskolin
(25 µM) or dexamethasone (10-8
M) were grown in DMEM supplemented with 10% stripped
serum. DNA (50–100 ng p91023-nurr1/nur77; 0.5–1 µg p-372CRF CAT and
p-483POMC CAT; 200 ng M2G-tk CAT) in a volume of 250 µl
HEPES-buffered saline was added to 1 x 1010 d1312
adenovirus particles (49) in a volume of 333 µl HEPES-buffered saline
and incubated at room temperature for 30 min. Poly-L-lysine
was added (the amount required was based on the size of the DNA used)
and incubated at room temperature for 30 min. The DNA-modified
virus-poly-L-lysine was added to the cells and incubated
for 2 h at 37 C. The virus-containing medium was removed, and 3 ml
of specific medium were added to the cells. The cells were incubated at
37 C for 24 h before harvesting. Pituitaries from adult mice
(BALB/c) were rapidly isolated intact. Four whole pituitaries were
pooled per sample and collected in DMEM containing 10% stripped serum
and equilibrated in a 95% air-5% CO2 mixture.
Northern Blot
Total RNA from cultured cells was isolated at specific times
after treatment. RNA was quantitated by UV absorption, and 20 µg of
total RNA were electrophoresed on a standard Northern gel and
transferred to nylon membrane (50). Nurr1 and nur77 cDNA probes spanned
the amino-terminal region to avoid cross-hybridization. All membranes
were probed under high stringency conditions.
CAT Assay
Each plate of cells was washed once with PBS without calcium and
magnesium, scraped into 1 ml TEN buffer (40 mM Tris, 1
mM EDTA, 150 mM NaCl, pH 8.0) and collected by
centrifugation at 13,000 rpm for 30 sec. Cells were resuspended in 250
mM Tris-HCl, pH 7.5, and lysed by four freeze/thaw cycles.
Protein concentrations were determined by the micro-plate Bradford
assay (51). CAT activity was determined by incubating 5–10 µg
protein with 0.2 µCi [3H]chloramphenicol (20
µCi/µmol) and 250 µM butryl-Coenzyme A in 100 µl
250 mM Tris-HCl, pH 7.5, for 3 h at 37 C. Acylated
chloramphenicol was extracted using a mixture of 200 µl 2:1
2,6,10,14-tetramethylpentadecane and Xylenes and counted in a
scintillation counter (52). The background of the CAT activity ranges
from 300–500 cpm and has been subtracted from the assay. Therefore,
1000 cpm represents a low but significant level of basal activity.
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ACKNOWLEDGMENTS |
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FOOTNOTES |
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Received for publication June 18, 1996. Revision received October 2, 1996. Accepted for publication October 22, 1996.
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REFERENCES |
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TOPABSTRACTINTRODUCTIONRESULTSDISCUSSIONMATERIALS AND METHODSREFERENCES |
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 J. Martinez-Gonzalez and L. Badimon The NR4A subfamily of nuclear receptors: new early genes regulated by growth factors in vascular cells Cardiovasc Res, February 15, 2005; 65(3): 609 - 618. [Abstract] [Full Text] [PDF]
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 J. C. Havelock, A. L. Smith, J. B. Seely, C. A. Dooley, R. J. Rodgers, W. E. Rainey, and B. R. Carr The NGFI-B family of transcription factors regulates expression of 3{beta}-hydroxysteroid dehydrogenase type 2 in the human ovary Mol. Hum. Reprod., February 1, 2005; 11(2): 79 - 85. [Abstract] [Full Text] [PDF]
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E Yamamori, M Asai, M Yoshida, K Takano, K Itoi, Y Oiso, and Y Iwasaki Calcium/calmodulin kinase IV pathway is involved in the transcriptional regulation of the corticotropin-releasing hormone gene promoter in neuronal cells J. Mol. Endocrinol., December 1, 2004; 33(3): 639 - 649. [Abstract] [Full Text] [PDF]
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V. Mynard, O. Latchoumanin, L. Guignat, J. Devin-Leclerc, X. Bertagna, B. Barre, J. Fagart, O. Coqueret, and M. G. Catelli Synergistic Signaling by Corticotropin-Releasing Hormone and Leukemia Inhibitory Factor Bridged by Phosphorylated 3',5'-Cyclic Adenosine Monophosphate Response Element Binding Protein at the Nur Response Element (NurRE)-Signal Transducers and Activators of Transcription (STAT) Element of the Proopiomelanocortin Promoter Mol. Endocrinol., December 1, 2004; 18(12): 2997 - 3010. [Abstract] [Full Text] [PDF]
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 M. Premzl, J. E. Gready, L. S. Jermiin, T. Simonic, and J. A. Marshall Graves Evolution of Vertebrate Genes Related to Prion and Shadoo Proteins--Clues from Comparative Genomic Analysis Mol. Biol. Evol., December 1, 2004; 21(12): 2210 - 2231. [Abstract] [Full Text] [PDF]
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 P. J. Peeters, H. W. Gohlmann, I. Van den Wyngaert, S. M. Swagemakers, L. Bijnens, S. U. Kass, and T. Steckler Transcriptional Response to Corticotropin-Releasing Factor in AtT-20 Cells Mol. Pharmacol., November 1, 2004; 66(5): 1083 - 1092. [Abstract] [Full Text] [PDF]
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M. H. Bassett, T. Suzuki, H. Sasano, C. J. M. de Vries, P. T. Jimenez, B. R. Carr, and W. E. Rainey The Orphan Nuclear Receptor NGFIB Regulates Transcription of 3{beta}-Hydroxysteroid Dehydrogenase: IMPLICATIONS FOR THE CONTROL OF ADRENAL FUNCTIONAL ZONATION J. Biol. Chem., September 3, 2004; 279(36): 37622 - 37630. [Abstract] [Full Text] [PDF]
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K. D. S. A. Wansa, J. M. Harris, G. Yan, P. Ordentlich, and G. E. O. Muscat The AF-1 Domain of the Orphan Nuclear Receptor NOR-1 Mediates Trans-activation, Coactivator Recruitment, and Activation by the Purine Anti-metabolite 6-Mercaptopurine J. Biol. Chem., June 27, 2003; 278(27): 24776 - 24790. [Abstract] [Full Text] [PDF]
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P. Ordentlich, Y. Yan, S. Zhou, and R. A. Heyman Identification of the Antineoplastic Agent 6-Mercaptopurine as an Activator of the Orphan Nuclear Hormone Receptor Nurr1 J. Biol. Chem., June 27, 2003; 278(27): 24791 - 24799. [Abstract] [Full Text] [PDF]
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H. Sadie, G. Styger, and J. Hapgood Expression of the Mouse Gonadotropin-Releasing Hormone Receptor Gene in {alpha}T3-1 Gonadotrope Cells Is Stimulated by Cyclic 3',5'-Adenosine Monophosphate and Protein Kinase A, and Is Modulated by Steroidogenic Factor-1 and Nur77 Endocrinology, May 1, 2003; 144(5): 1958 - 1971. [Abstract] [Full Text] [PDF]
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M. Maira, C. Martens, E. Batsche, Y. Gauthier, and J. Drouin Dimer-Specific Potentiation of NGFI-B (Nur77) Transcriptional Activity by the Protein Kinase A Pathway and AF-1-Dependent Coactivator Recruitment Mol. Cell. Biol., February 1, 2003; 23(3): 763 - 776. [Abstract] [Full Text]
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V. Mynard, L. Guignat, J. Devin-Leclerc, X. Bertagna, and M. G. Catelli Different Mechanisms for Leukemia Inhibitory Factor-Dependent Activation of Two Proopiomelanocortin Promoter Regions Endocrinology, October 1, 2002; 143(10): 3916 - 3924. [Abstract] [Full Text] [PDF]
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D. Kovalovsky, D. Refojo, A. C. Liberman, D. Hochbaum, M. P. Pereda, O. A. Coso, G. K. Stalla, F. Holsboer, and E. Arzt Activation and Induction of NUR77/NURR1 in Corticotrophs by CRH/cAMP: Involvement of Calcium, Protein Kinase A, and MAPK Pathways Mol. Endocrinol., July 1, 2002; 16(7): 1638 - 1651. [Abstract] [Full Text] [PDF]
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A. Lacroix, N. N'Diaye, J. Tremblay, and P. Hamet Ectopic and Abnormal Hormone Receptors in Adrenal Cushing's Syndrome Endocr. Rev., February 1, 2001; 22(1): 75 - 110. [Abstract] [Full Text]
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S. Tetradis, O. Bezouglaia, and A. Tsingotjidou Parathyroid Hormone Induces Expression of the Nuclear Orphan Receptor Nurr1 in Bone Cells Endocrinology, February 1, 2001; 142(2): 663 - 670. [Abstract] [Full Text] [PDF]
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 R. Newton Molecular mechanisms of glucocorticoid action: what is important? Thorax, July 1, 2000; 55(7): 603 - 613. [Full Text]
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M. Maira, C. Martens, A. Philips, and J. Drouin Heterodimerization between Members of the Nur Subfamily of Orphan Nuclear Receptors as a Novel Mechanism for Gene Activation Mol. Cell. Biol., November 1, 1999; 19(11): 7549 - 7557. [Abstract] [Full Text] [PDF]
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V. Giguère Orphan Nuclear Receptors: From Gene to Function Endocr. Rev., October 1, 1999; 20(5): 689 - 725. [Abstract] [Full Text]
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N. Sugino, M. Zilberstein, R. K. Srivastava, C. M. Telleria, S. E. Nelson, M. Risk, J. Y. Chou, and G. Gibori Establishment and Characterization of a Simian Virus 40-Transformed Temperature-Sensitive Rat Luteal Cell Line Endocrinology, April 1, 1998; 139(4): 1936 - 1942. [Abstract] [Full Text] [PDF]
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Y. Iwasaki, Y. Oiso, H. Saito, and J. A. Majzoub Positive and Negative Regulation of the Rat Vasopressin Gene Promoter Endocrinology, December 1, 1997; 138(12): 5266 - 5274. [Abstract] [Full Text] [PDF]
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