Endocrinology Vol. 139, No. 1 195-203
Copyright © 1998 by The Endocrine Society
Stimulation of the Preprothyrotropin-Releasing Hormone Gene by Epidermal Growth Factor
Ying Ren,
Teturou Satoh,
Masanobu Yamada,
Koshi Hashimoto,
Shuntaro Konaka,
Toshiharu Iwasaki and
Masatomo Mori
First Department of Internal Medicine, Gunma University School of
Medicine, Maebashi 371, Japan
Address all correspondence and requests for reprints to: Teturou Satoh, M.D., Ph.D., First Department of Internal Medicine, Gunma University School of Medicine, 339-15 Showa-machi, Maebashi 371, Japan.
 |
Abstract
|
|---|
Regulation of the expression of the prepro-TRH (ppTRH) gene by
epidermal growth factor (EGF) was investigated. The ip injection of EGF
significantly stimulated hypothalamic ppTRH messenger RNA levels in
rats. To clarify whether this stimulatory effect of EGF could be
exerted at the level of gene transcription, the 5'-flanking region
(-1893/+127) of the mouse ppTRH gene fused to a luciferase reporter
gene was transiently transfected into pituitary
GH4C1 cells, and the effect of EGF on gene
transcription was measured by a luciferase assay. EGF stimulated ppTRH
gene promoter activity in a time- and dose-dependent manner. Deletion
analysis revealed that two different regions of the promoter, between
-254 and -218 [EGF response element-1 (EGFRE1)] and between -130
and -84 (EGFRE2) were required for full stimulation by EGF. The two
EGFREs possessed putative binding sequences for the transcription
factor Sp1, and they functioned cooperatively in heterologous
promoters. Nuclear extracts from GH4C1 cells
specifically bound those two EGFREs in gel retardation assays. Two
protein-DNA complexes were found on EGFRE1, whereas four complexes were
observed on EGFRE2. Although the binding of nuclear extracts to EGFRE1
was competed for by the consensus Sp1 binding sequence, the complexes
on EGFRE1 were not supershifted by an Sp1 antibody. Formation of the
slower migrating protein complex on EGFRE1 was prevented by EDTA,
suggesting that one of the EGFRE1-binding proteins might be an
Sp1-related zinc finger protein. Competition and supershift experiments
demonstrated that the EGFRE2-binding protein showing that the slowest
migration possessed a characteristic similar to that of Sp1. Selective
mutations of the Sp1-binding site in EGFRE2 markedly diminished the
EGF-induced stimulation. These results suggest that EGF may function as
a positive regulator of ppTRH gene expression, and that the stimulatory
effect may be mediated through a cooperative interaction between Sp1 or
Sp1-related proteins and additional factors that bind to two separate
DNA regions.
 |
Introduction
|
|---|
TRH IS A hypothalamic tripeptide that
regulates thyroid function by stimulating the synthesis and secretion
of TSH in the anterior pituitary gland (1). TRH is derived from a large
precursor protein, prepro-TRH (ppTRH), by posttranscriptional
processing and enzymatic modification (2). Via a feedback mechanism,
expression of the hypothalamic ppTRH gene is negatively regulated by
thyroid hormone (3, 4). We recently cloned human and mouse ppTRH genes
(5, 6) and characterized the negative response DNA element for thyroid
hormone in their promoter regions (6, 7). The levels of hypothalamic
ppTRH messenger RNA (mRNA) have been reported to be negatively
regulated by glucocorticoid and food deprivation (8, 9). Although the
negative regulation of ppTRH gene expression in the hypothalamus has
been well studied, as noted above, the factors directly stimulating
expression of the hypothalamic ppTRH gene have not been identified.
Epidermal growth factor (EGF), a growth factor initially isolated from
the mouse salivary gland (10), is distributed throughout the body and
elicits a number of biological responses for cell differentiation and
growth (11). In addition, EGF has been reported to stimulate the
synthesis and release of several hormones in the pituitary gland. It
has been established that EGF stimulates pituitary PRL synthesis at the
level of gene transcription through the serum response element of the
PRL gene promoter (12, 13). EGF has also been reported to stimulate TSH
secretion from perfused rat pituitary glands (14). The iv
administration of EGF stimulates TSH release in vivo (14).
Fan et al. recently reported that cold stress induced the
expression of EGF and its receptor mRNA in pituitary thyrotrophs in
rats, suggesting that EGF may have autocrine and/or paracrine roles in
the maintenance of the TSH response to cold (15). Although these
findings indicated that EGF may modulate thyroid function at the
pituitary level by stimulating TSH release in response to some stresses
such as cold exposure, the possibility that TSH secretion is augmented
by EGF stimulation of the synthesis and secretion of hypothalamic TRH
in vivo cannot be ruled out.
It is well known that cold exposure increases the blood level of TSH
and thyroid hormone by stimulating the secretion of TRH from the median
eminence in the hypothalamus (16). In addition to its stimulatory
effect on TRH release, acute and chronic cold exposure elevates the
cellular level of TRH mRNA (17, 18). Although several
neurotransmitters, such as catecholamines, serotonin, and
-aminobutyric acid, appear to be involved in the cold
exposure-induced TRH release from the median eminence (16), the factors
directly stimulating TRH gene expression by cold remain to be
determined. Several growth factors, including EGF, have been reported
to be synthesized locally in the hypothalamus (19, 20). In response to
stress, EGF has been postulated to function as a stimulator of the
hypothalamic-pituitary-adrenal axis, and its site of action appears to
be at the levels of both the hypothalamus and the pituitary (21, 22).
It has been reported that transforming growth factor-
, a member of
the EGF family, stimulates the release of hypothalamic LHRH (23). Taken
together, these results prompted us to evaluate the possible regulatory
roles of EGF regarding the action of hypothalamic TRH. In the present
study we found that EGF stimulated ppTRH gene expression both in
vivo and in vitro. Transfection studies using
GH4C1 cells revealed that the stimulatory
effects may be mediated by direct activation of gene transcription
through two separate DNA regions in the TRH gene promoter. We also
found that a transcription factor, Sp1, in cooperation with other
transcription factors might mediate the stimulatory effect of EGF on
mouse TRH gene transcription.
 |
Materials and Methods
|
|---|
Animal treatment
Male Sprague-Dawley rats, weighing 200 g (n = 6), were
housed in light- and temperature-controlled conditions under a 12-h
light, 12-h dark cycle, with food and water available ad
libitum. Seven days after their arrival, the rats were injected ip
with EGF (20 µg/kg BW; Becton Dickinson Labware, Bedford, MA) every
8 h for 3 days. The dose of EGF injected in the rats
(10-5 M) was identical to that used in a
previous study which stimulated the release of pituitary TSH in
vivo (14). Control rats received vehicle isotonic saline
injections according to the same schedule. One hour after the final
injection of EGF, the rats were killed by decapitation, and the
anterior hypothalami were dissected and frozen immediately in liquid
nitrogen.
RNA isolation and Northern blot analysis
Total RNA was isolated from individual hypothalami, and Northern
blot analysis was performed using a 32P-labeled rat ppTRH
complementary RNA probe as described previously (24). The density of
the hybridization signals was quantitated by a laser densitometer.
Cell culture
GH4C1, GH3, CV-1, HeLa, and
I-10 cells were grown in DMEM supplemented with 10% (vol/vol) FBS,
penicillin, streptomycin, and amphotericin B as described previously
(6).
Plasmid construction
Plasmids -1893/+127 Luc and -254/+127 Luc were described
previously (6), in which -1893/+127 and -254/+127 fragments of the
5'-flanking region of the mouse ppTRH gene, respectively, were ligated
to a reporter gene, pA3Luc, possessing the firefly luciferase
complementary DNA as a reporter (25, 26) (provided by Dr. William M.
Wood). DNA fragments containing various lengths of the 5'-flanking
region of the mouse ppTRH gene were amplified by PCR using the
-1893/+127 fragment in pGEM4Z (Promega, Madison, WI) as a template.
All sense primers for PCR were designed from the nucleotide sequence of
the mouse ppTRH gene reported by us (6) and contained a
HindIII site in the middle of the primers by changing 1 or 2
bp (bp) from the original sequence to facilitate subsequent subcloning.
A common antisense primer (PCR2) corresponding to the region between
+68 and +91 was used for PCR, which also contained a HindIII
site by changing the C residue at +82 to T. All of the PCR-amplified
5'-flanking sequences, therefore, ended at the same position. The
amplified DNA fragments were cut by HindIII and subcloned
into pGEM4Z, and the nucleotide sequences were verified by the dideoxy
chain termination method (27) using Sequenase version 2 (U.S.
Biochemical Corp., Cleveland, OH). Sequence-confirmed DNA fragments
were subcloned into a unique HindIII site of the
pA3Luc, and the orientation of the inserts was confirmed by
sequencing.
Oligonucleotides
The nucleotide sequences of the upper strand of
oligonucleotides used for the construction of heterologous promoters
and the gel mobility shift assays were as follows (lowercase letters
indicate HindIII linker sequences, and
underlining indicates putative Sp1-binding sites and point
mutations introduced); EGF response element-1 (EGFRE1),
5'-agcTTCCCGGGACGGTCTCTCTCCCTCCCTTTGTTCCCTAGTCAGAGTGTa-3';
EGFRE2, 5'-agcttGGTTTCCGGAAAGCGGGCGGGTCCCCCGGCTCTGCC
GTCAGCGCCCCTa-3'; consensus Sp1,
AGTCGATCGGGGCGGGGCGA-3'; mutant Sp1,
5'-AGTCGATCGGTTCGGGGCGA-3'; and palindromic thyroid
hor-mone response element (TREPAL),
5'-AGTCATCAGGTCATGA-CCTGCGA-3'.
Heterologous promoters
A heterologous promoter (EGFRE1 and -2-TK-Luc) was constructed
by insertion of the SmaI/XhoI fragment (-254 to
-37) of the mouse ppTRH gene into pT109Luc, which possesses the
minimal promoter of the herpes simplex virus thymidine kinase (TK) gene
fused to the luciferase gene (28). EGFRE1-TK- and EGFRE2-TK-Luc were
constructed by the insertion of a single copy of synthetic
oligonucleotide corresponding to the region from -258 to -213
(EGFRE1) or from -130 to -84 (EGFRE2), respectively, into a unique
HindIII site of pT109Luc.
PCR-generated site-directed mutagenesis
Point mutations were introduced into the Sp1-binding site at
-117 by sequential PCR steps as described previously (29). Two PCR
fragments encompassing the mutation were amplified, using the
-1893/+127 fragment as the template by the combination of a sense
primer (PCR1; 5'-CAAGCACAGGTGCCACTAGAT-3'; residues -381 to -359) and
a mutant antisense primer (5'-CAGAGCCGGGGGACCCGAACGCTT-3';
residues -121 to -97) and by the combination of a mutant sense primer
(5'-CGGAAAGCGTTCGGGTCCCCCGGCT-3'; residues -125 to -101)
and an antisense primer (PCR2; 5'-GACTCTGCAAAGCTTTCCAAGATG-3'; residues
+68 to +91). The mutant sense and antisense primers overlapped one
another by 20 bp. The two PCR products of the expected lengths were gel
purified, heat denatured, and then annealed to each other. The 3'-ends
were extended by a Taq DNA polymerase and amplified using
the PCR1 and PCR2 primers. The final PCR product was digested by
SmaI and HindIII and subcloned into pGEM4Z. The
introduced mutation was confirmed by dideoxy sequencing, and the
SmaI/HindIII fragment (-254/+83) was subcloned
into the SmaI/HindIII sites of pA3Luc.
Transient transfection and luciferase assay
Transient transfection into GH4C1 cells
was performed by a calcium phosphate precipitation method with 3 µg
reporter constructs as reported previously (5). Glycerol shock was
performed for 2 min, 16 h after transfection. The cells were
incubated for an additional 48 h in the presence or absence of EGF
(100 nM; Collaborative Biomedical Products, Waltham, MA;
culture grade). The luciferase assay was carried out as described
previously (5). The protein concentrations were measured by Bradfords
method (30), and the luciferase activities were normalized by protein
concentration and expressed as light units per µg protein.
Nuclear extracts
Nuclear extracts from HeLa cells were purchased from Stratagene
(La Jolla, CA). Nuclear extracts from GH4C1
cells were prepared according to the method of Andrews et
al. (31). In brief, confluent GH4C1 cells
in a 100-mm culture dish were rinsed twice with ice-cold PBS and then
scraped into 0.75 ml PBS. The cells were spun down; resuspended in 200
µl buffer A containing 10 mM HEPES-KOH (pH 7.9), 1.5
mM MgCl2, 10 mM KCl, 0.5
mM dithiothreitol, and 0.2 mM
phenylmethylsulfonylfluoride (Sigma Chemical Co., St. Louis, MO); and
allowed to swell on ice for 10 min. After centrifugation, nuclear
pellets were resuspended in 50 µl buffer C containing 20
mM HEPES-KOH (pH 7.9), 25% glycerol, 420 mM
NaCl, 1.5 mM MgCl2, 0.2 mM EDTA,
0.5 mM dithiothreitol, and 0.2 mM
phenylmethylsulfonylfluoride. After incubation on ice for 20 min
followed by a quick spin, the supernatant was used as the nuclear
extract. The protein concentration was determined as described above,
using BSA as a standard.
Gel mobility shift assays
The double strand oligonucleotides described above were
radiolabeled by fill-in reaction with [
-32P]deoxy-CTP
(New England Nuclear, Boston, MA) and were separated from
unincorporated isotopes using Sephadex G-25 columns (Boehringer
Mannheim, Mannheim, Germany). Binding reactions were performed with
50,000 cpm purified probes and 1 µg nuclear extract for 20 min under
conditions described previously (6). For competition experiments, a
200-fold molar excess of cold oligonucleotides was included unless
otherwise indicated. For supershift experiments, either 2 µl of a
specific rabbit polyclonal antibody for the human Sp1 that cross-reacts
to the rat Sp1 (Santa Cruz Biotechnology, Santa Cruz, CA) or normal
rabbit serum (NRS) was incubated for an additional 30 min at room
temperature. Gel electrophoresis and autoradiography were performed as
previously described (6).
 |
Results
|
|---|
EGF injection stimulates the levels of hypothalamic ppTRH mRNA
The chronic EGF treatment increased the rats steady state levels
of hypothalamic ppTRH mRNA (Fig. 1A
). The
densitometric analysis revealed that EGF significantly stimulated TRH
mRNA levels by 2-fold (Fig. 1B
). Although we did not measure EGF levels
in the hypothalamus, EGF has been suggested to be transported to the
central nervous system from the peripheral circulation through the
choloid plexuses, which constitute the blood-cerebrospinal fluid
barrier (32).

View larger version (17K):
[in this window]
[in a new window]
|
Figure 1. Chronic EGF treatment stimulated the steady state
level of hypothalamic TRH mRNA in rats. A, Northern blot analysis of
the hypothalamic TRH mRNA (1.6 kilobases) using a
32P-labeled rat TRH complementary RNA probe. The position
of 18S ribosomal RNA is indicated. RNA loading is shown by ethidium
bromide staining of the gel. B, Densitometric analysis of hybridization
signals. EGF-treated rats showed significantly higher signals (*,
P < 0.05) when analyzed by Students
t test.
|
|
EGF stimulates ppTRH gene transcription in a dose- and
time-dependent manner in vitro
We recently isolated the mouse ppTRH gene and characterized its
5'-flanking sequence -2 kilobases from the transcription start site
(6). Using the 5'-flanking sequence (-1893/+127) fused to the firefly
luciferase gene, we examined whether EGF stimulation of TRH gene
expression was mediated directly by stimulation of ppTRH gene
transcription using transient transfection into
GH4C1 cells. We used this cell line because
hypothalamic neuronal cell lines expressing the endogenous TRH were not
available, and the activity of the transfected ppTRH gene promoter in
GH4C1 cells was much higher than that in other
cell lines, including GH3 cells, HeLa cells, CV-1 cells,
and mouse I-10 cells, which were derived from testicular Leydig cell
tumors (data not shown). Moreover,
GH4C1 cells are known to
express functional EGF receptors (33, 34). After transfection, the
cells were exposed to graded doses of EGF, and the luciferase
activities were measured after 48 h. As shown in Fig. 2A
, EGF stimulated TRH gene transcription
in a dose-dependent manner. Significant stimulation was observed at
10-10 M EGF. Approximately 4-fold stimulation
compared with the control value was observed at 10-9
M, but no additional stimulation was observed at
10-8 M EGF. We next studied the time course of
EGF stimulation of TRH gene transcription (Fig. 2B
). The luciferase
activities in EGF-treated and control groups at 6 and 12 h did not
differ from those at time zero. TRH gene transcription was
significantly stimulated after 24 h until 48 h by the
addition of 10-8 M EGF, and it decreased
thereafter.

View larger version (14K):
[in this window]
[in a new window]
|
Figure 2. A, Dose-dependent stimulation of the mouse ppTRH
gene promoter by EGF. The 5'-flanking region (-1893/+127) of the mouse
ppTRH gene fused to the luciferase reporter gene was transfected into
GH4C1 cells with increasing concentrations of
EGF. Luciferase activities were measured after 48 h and are
expressed as light units per µg protein. The data are the mean
± SE of three experiments with triplicate determinants.
Statistical analysis was performed using Duncans multiple range test.
Asterisks indicate a significant difference
(P < 0.05) from luciferase activity without EGF.
B, The time course of EGF stimulation of the ppTRH gene promoter. After
transfection, cells were harvested following 0-, 6-, 12-, 24-, 48-, and
72-h exposures to EGF. Cells without EGF treatment were harvested
according to the same schedule. The data are the mean ±
SE of triplicate plates. The experiment was performed twice
with identical results. The luciferase activities after 24, 48, and
72 h of treatment were significantly higher than those of control
groups.
|
|
EGF response elements in the mouse ppTRH gene are located at two
separate regions
To delineate the DNA elements responsive to EGF stimulation in the
TRH gene promoter, a series of deletion mutants of the 5'-flanking
sequence was constructed and transfected with or without
10-8 M EGF. As shown in Fig. 3
, EGF stimulated the promoter activity
of the longest construct (-1893/+127) by approximately 5-fold. In
contrast, no significant stimulation was observed in the herpes simplex
virus TK gene promoter. The deletion from -1893 to -255 (-254/+127)
did not significantly influence EGF stimulation. In contrast, EGF
activation was significantly decreased from 5- to 2-fold by deletion of
the sequence between -254 and -218 (-217/+83). The further deletion
of fragments between -217 and -178 (-177/+83) and between -177 and
-131 (-130/+83) did not affect EGF stimulation. Finally, deletion of
the element between -130 and -84 (-83/+83) completely abolished the
EGF stimulatory effect. No significant stimulation was observed in the
-36/+127 construct. These deletion analyses indicated that the DNA
elements mediating EGF stimulation of the mouse ppTRH gene were located
at two separate regions, i.e. between -254 and -218 and
between -130 and -84. We designated the upstream region EGFRE1 and
the downstream region EGFRE2.

View larger version (12K):
[in this window]
[in a new window]
|
Figure 3. Delineation of the EGFRE in the mouse ppTRH gene
promoter. Deletion mutants of the 5'-flanking region of the mouse ppTRH
gene were transfected, and luciferase activities were measured after
48-h exposure to 10 nM EGF. The data are presented as fold
stimulation in the presence of EGF and are the mean ±
SE of at least three separate experiments. Statistical
analysis was performed using Duncans multiple range test. The fold
stimulations of the -1893 and -254 constructs were significantly
higher (P < 0.05) than those of the -217, -177,
and -130 constructs (*). The fold stimulations of the -217, -177,
and -130 constructs were significantly higher (P
< 0.05) than those of the -83 and -36 constructs (**).
|
|
Nucleotide sequences of the two EGFREs contain putative Sp1-binding
sites
Figure 4
shows the nucleotide
sequences of the two EGF response elements identified by deletion
analysis. The nucleotide sequence of EGFRE1 is TC rich, and contains a
sequence (TCCCTCCC) homologous to a novel Sp1-binding site identified
in the acetylcholine receptor
3 gene promoter (CCCCTCCC) (35). It
also possesses a sequence (GGGACG) similar to the GA box (GGGAGG) found
in the glial-specific JC virus early promoter (36) that binds Sp1. In
contrast, the EGFRE2 sequence is GC rich and possesses a consensus core
hexamer of the Sp1-binding site (GGGCGG) (37).

View larger version (17K):
[in this window]
[in a new window]
|
Figure 4. Nucleotide sequences of the two EGFREs identified
by deletion analysis. Putative Sp1-binding sites homologous to known
Sp1-binding sites in other genes are underlined.
|
|
The two EGFREs function cooperatively in a heterologous
promoter
To assess whether these two regions function as EGFREs in a
heterologous promoter, a DNA fragment including the two EGFREs (EGFRE1
and -2-TK-Luc) or an individual fragment of each response element
(EGFRE1- and EGFRE2-TK-Luc) was separately linked to a TK gene
promoter. The heterologous promoter activities were normalized by the
wild TK promoter activities transfected in parallel. The addition of
EGFREs to the TK promoter did not alter the basal promoter activity of
TK-Luc (data not shown). As shown in Fig. 5
, EGF stimulated EGFRE1 and -2-TK-Luc
significantly, by 1.8-fold. In contrast, neither EGFRE1-TK-Luc nor
EGFRE2-TK-Luc was stimulated by EGF. These results indicated that the
two separate EGF response elements in the ppTRH gene promoter may
function in a cooperative manner. Moreover, the fold stimulation of the
EGFRE1 and -2-TK-Luc by EGF was significantly lower than that of the
wild-type promoter, suggesting that the positioning of the two EGFREs
relative to the transcription start site affects the magnitude of EGF
stimulation.

View larger version (22K):
[in this window]
[in a new window]
|
Figure 5. Effect of EGF on the heterologous reporter genes
transfected into GH4C1 cells. A DNA fragment
(-254/-36) containing the two EGFREs or single copies of EGFRE1 and
EGFRE2 were ligated in front of the TK-Luc. The data are presented as
fold stimulation in the presence of EGF, and are the mean ±
SE of three transfections with triplicate plates.
|
|
Transcription factor Sp1 binds to EGFRE2 in vitro
To determine whether the nuclear proteins extracted from
GH4C1 cells bind to the two
EGFREs, two EGFRE oligonucleotides were individually radiolabeled,
incubated with nuclear extracts, and resolved in nondenaturing
polyacrylamide gels. A no protein-DNA complex was observed with either
probe when mixed with unprogrammed rabbit reticulocyte lysates (Fig. 6A
, lane 2 in both panels). With the
EGFRE1 probe, an intense, fast migrating complex B was observed in
addition to a weaker, slowly migrating complex A (lanes 3 and 4 in the
left panel). In contrast, with the EGFRE2 probe, one intense
DNA-protein complex C, migrating in a position similar to that of
complex A on EGFRE1, was observed with three additional faster
migrating complexes, D, E, and F (lanes 3 and 4 in the right
panel). Complex F was present in a position similar to that of
complex B on EGFRE1. No new protein-DNA complexes were observed on
either probe with nuclear extracts from EGF-treated
GH4C1 cells (lanes 5 and 6
in both panels). DNA-protein complexes identical to those detected with
HeLa cells were found with
GH4C1 cell nuclear extracts
on both probes (data not shown).

View larger version (76K):
[in this window]
[in a new window]
|
Figure 6. Characterization of GH4C1
cell nuclear proteins binding to EGFREs by electrophoretic mobility
shift assays. A, Mobility shift assays of two EGFREs with
GH4C1 nuclear extracts. The two radiolabeled
EGFREs were incubated with unprogrammed rabbit reticulocyte lysates or
two different concentrations of nuclear extracts from nontreated or
48-h EGF-treated GH4C1 cells. B, Comparison of
nuclear protein binding to EGFRE2 with that to the 10-bp Sp1 consensus
sequence. Radiolabeled EGFRE2 or the consensus Sp1 sequence was mixed
with GH4C1 nuclear extracts and was separated
in parallel. A 200-fold molar excess of unlabeled consensus Sp1-binding
sequence, EGFRE1, EGFRE2, or TREPAL was added as the competitor to the
reaction mixtures. C, Competition by a mutant Sp1 sequence of binding
of nuclear proteins to EGFRE2. Graded amounts (200-, 100-, 50-, and
20-fold molar excesses) of an established mutant Sp1 sequence (mutSp1)
were used as a competitor, as were EGFRE2, the consensus Sp1 sequence
(Sp1), and TREPAL. D, Supershift experiments using a specific antibody
for Sp1. Two microliters of an Sp1 antibody (Sp1Ab) or NRS were added
to the reaction mixtures. After a 20-min incubation, samples were
resolved by electrophoresis. Arrowheads indicate the
supershifted protein-DNA complexes.
|
|
Because the EGFRE2 sequence contained a consensus sequence for the
binding site of transcription factor Sp1, we next compared the pattern
of protein binding to the EGFRE2 probe with that to the consensus
Sp1-binding site. As shown in Fig. 6B
, four similar DNA-protein
complexes formed on EGFRE2 were detected with the consensus Sp1 site
(compare lanes 2 in the two panels). Complexes C, D, E, and F formed on
the Sp1 oligonucleotide were diminished by incubation with an excess of
cold EGFRE2 (lane 5 in the left panel). Conversely, the
formation of these four DNA-complexes on EGFRE2 was completely
abolished by incubation with unlabeled Sp1 oligonucleotides (lane 5 in
the right panel). Unlabeled Sp1 oligonucleotide more
effectively inhibited formation of protein-DNA complexes on EGFRE2 than
did cold EGFRE2 itself (Fig. 6C
). Unlabeled EGFRE1 did not affect the
four DNA-protein complexes on the Sp1 probe (lane 4 in the left
panel), but slightly reduced the complex formation on the EGFRE2
probe (lane 3 in the right panel). A mutant Sp1
oligonucleotide in which the second and third G residues in the GGGCGG
motif were substituted by T residues failed to prevent formation of the
four DNA-protein complexes (Fig. 6C
). Furthermore, a TREPAL
oligonucleotide, with no relation to the Sp1-binding site, did not
inhibit the formation of these complexes (Fig. 6C
). These results
suggest that the formation of all four complexes on the GGGCGG motif in
EGFRE2 was specific.
To assess whether the nuclear protein bound to EGFRE2 was bona
fide Sp1, a specific antibody for Sp1 was added to the reaction
mixtures. As shown in Fig. 6D
, an anti-Sp1 antibody, but not NRS,
supershifted complex C on the EGFRE2 and Sp1 probes, confirming that
the major nuclear protein binding to EGFRE2 was the transcription
factor Sp1. In contrast, complexes D, E, and F on both probes were not
supershifted by the Sp1 antibody.
Two distinct classes of nuclear proteins bind to EGFRE1
The binding of nuclear proteins to the EGFRE1 probe was also
reduced by the consensus Sp1 oligonucleotide in a manner similar to
that by cold EGFRE1 itself (Fig. 7
).
However, higher concentrations of unlabeled Sp1 oligonucleotide were
required to compete with the binding on the EGFRE1 probe compared with
the competition of binding to the EGFRE2 probe (Figs. 6C
and 7
). The
major protein-DNA complex B on EGFRE1 migrated faster than did complex
C on EGFRE2 (Fig. 6A
), and complex A was retarded in a position similar
to that of complex C on EGFRE2 (Fig. 6A
). The two complexes, A and B,
on EGFRE1 were not supershifted by an Sp1 antibody (data not shown).
These results imply that the EGFRE1-binding proteins were able to bind
to the consensus Sp1 sequence with low affinity and were
distinguishable from the authentic Sp1. We next examined whether the
EGFRE1-binding proteins were the Sp1-related protein that also
possesses zinc finger motifs (38, 39). The zinc finger motif requires
zinc as a cofactor and can be eliminated by the chelation of zinc ions
by adding EDTA to the binding buffer (40). As shown in Fig. 8A
, the addition of EDTA at a dose as low
as 5 mM diminished the complexes C and E on the EGFRE2
probe. In contrast, complexes D and F on EGFRE2 were not affected, even
by 50 mM EDTA. These data suggest that complex C on the
EGFRE2 probe has a nature compatible with that of Sp1. Complex A on the
EGFRE1 probe was obviously sensitive to ETDA, as were complexes C and E
on the EGFRE2 probe (Fig. 8B
), but the formation of complex B was not
prevented by 50 mM EDTA. Addition of increasing
concentrations of CaCl2 in the presence of 50
mM EDTA did not restore binding of all EDTA-sensitive
protein-DNA complexes (data not shown). These results indicate that two
distinctive classes of nuclear proteins could bind to EGFRE1, and that
the protein-forming complex A might be an Sp1-related zinc finger
protein.

View larger version (51K):
[in this window]
[in a new window]
|
Figure 7. The binding of GH4C1
nuclear proteins to EGFRE1 was competed for by the consensus Sp1
sequence. Radiolabeled EGFRE1 was incubated with
GH4C1 nuclear extracts in the presence or
absence of increasing amounts (0-, 20-, 50-, 100-, and 200-fold molar
excesses) of cold EGFRE1 or Sp1 oligonucleotides.
|
|

View larger version (64K):
[in this window]
[in a new window]
|
Figure 8. Effect of chelation agent EDTA on the formation of
protein-DNA complexes on EGFRE1 and -2. Increasing concentrations
(050 mM) of EDTA were added to binding reaction mixtures,
and they were incubated for 20 min.
|
|
Mutation of the consensus Sp1 site in EGFRE2 reduces EGF
stimulation of the ppTRH gene
To determine whether a mutation of the GC box of EGFRE2
could abolish EGF-induced stimulation of ppTRH gene transcription, we
introduced point mutations into the consensus Sp1-binding site in the
-254/+83 Luc as employed in the gel shift assay (GGGCGG to GTTCGG). As
shown in Fig. 9
, EGF stimulation was
significantly reduced in the mutant -254/+83 Luc to approximately 40%
of that in the wild-type promoter. The result further confirmed that
the GGGCGG motif in EGFRE2 was necessary for the binding of a nuclear
protein such as Sp1 to confer the maximal EGF stimulatory action on the
mouse ppTRH gene promoter.

View larger version (12K):
[in this window]
[in a new window]
|
Figure 9. Site-directed mutagenesis of the Sp1 site in
EGFRE2 reduced the EGF responsiveness of the mouse ppTRH gene promoter.
Point mutations were introduced into the Sp1 sequence in EGFRE2 to
prevent the binding of Sp1 (mutant -254/+83 Luc). EGF stimulation of
the mutant plasmid was compared with that of the wild -254/+83 Luc.
Data are presented as fold stimulation in the presence of EGF and are
the mean ± SE of three transfections performed with
triplicate plates. The asterisk indicates a significant
difference (P < 0.01).
|
|
 |
Discussion
|
|---|
The present results provide new evidence that the administration
of EGF stimulates the level of hypothalamic ppTRH mRNA in rats, and
that transcription of the ppTRH gene is directly stimulated by EGF in
GH4C1 cells. The deletion
analysis revealed that the full EGF stimulation required two
cis-acting DNA elements spanning from -254 to -218
(EGFRE1) and from -130 to -83 (EGFRE2). Nuclear proteins from
GH4C1 cells specifically
bound to the two EGFREs in the electrophoretic mobility shift assay.
Competition and immunosupershift experiments in the electrophoretic
mobility shift assay established that the transcription factor Sp1 was
able to bind to the GGGCGG motif in EGFRE2. The consensus Sp1
oligonucleotide more efficiently inhibited protein-DNA complex
formation on the EGFRE2 probe than did the unlabeled EGFRE2 itself.
This is perhaps because the nucleotide sequence of the Sp1-binding site
in EGFRE2, CGGGCGGGTC, differed in two nucleotides
(underlined) from the 10-bp consensus Sp1-binding site,
G/TG/AGGC/AGG/TG/AG/AC/T (41). Such differences
might influence the binding affinity of Sp1 to the target sequence.
Three additional protein-DNA complexes (complexes D, E, and F) were
observed on EGFRE2, as were seen on the 10-bp consensus Sp1 sequence.
The formation of multiple complexes between nuclear extracts containing
the Sp1 and a consensus Sp1 probe has been reported by several groups
(38, 39, 42). However, binding factors other than Sp1 have not been
fully characterized. In the present study, the consensus Sp1 sequence
inhibited the formation of these three complexes on the EGFRE2 probe.
Moreover, mutant Sp1 oligonucleotides failed to inhibit the formation
of these complexes, and an Sp1 antibody did not supershift the three
complexes. These results indicate that nuclear proteins other than Sp1
can bind to the GGGCGG motif in EGFRE2. As the formation of one of
these complexes was sensitive to EDTA, the protein forming complex E
may be an Sp1-related protein that bound to the GC box by zinc finger
motifs but was different in structure from the authentic Sp1.
Alternatively, complex E may represent a partially degraded Sp1-DNA
complex that was not recognized by an Sp-1 antibody, as the antibody
used in the present study was raised against amino acid residues
436454 of the human Sp1 protein, and these amino acids were not
involved in DNA binding (43).
Homologous sequences to Sp1-binding sites identified in other genes
(35, 36) were found in the EGFRE1 sequence. However, our competition
and supershift analyses demonstrated that the
GH4C1 cell nuclear proteins
binding to EGFRE1 were distinct from authentic Sp1. As the formation of
two complexes on EGFRE1 was differentially affected by EDTA, it was
unlikely that the slower migrating band represented oligomerization of
the faster migrating one. It is plausible that two different classes of
nuclear proteins in GH4C1
cells, which could bind to the Sp1 sequence with lower affinities, may
bind to EGFRE1. The protein forming the slower migrating complex on
EGFRE1 might also be an Sp1-related zinc finger protein because of its
sensitivity to EDTA.
Our transfection studies with heterologous promoters demonstrated that
the two EGFREs did not confer EGF stimulation when an individual
element was linked to the TK promoter. No stimulatory effect on
heterologous promoter activities by EGF has been reported in the EGFREs
of other genes fused to the TK gene promoter (44). However, when the
DNA fragment containing both EGFREs of the mouse TRH gene was ligated
to the TK promoter, the heterologous promoter was significantly
stimulated by EGF. These results suggest that the two EGFREs of the
mouse TRH gene may mediate EGF stimulation in a cooperative manner. In
contrast, a point mutation introduced into EGFRE2 reduced EGF
stimulation by approximately 40%, indicating that EGFRE1 can partially
mediate EGF stimulation when positioned properly in a homologous
promoter. Taken together, these results suggest that the spatial
constraint between the two EGFREs and the transcription start site are
important factors in the exertion of full EGF stimulation. The
requirement for other DNA-binding proteins in addition to Sp1 for full
EGF stimulation of the mouse ppTRH gene might be reinforced by the
finding that the TK gene promoter, in which Sp1 plays an important role
for basal promoter function (37, 41), was not activated by EGF. A
cooperative interaction between EGFRE1- and EGFRE2-binding proteins
might be necessary to exert maximal EGF stimulation of the mouse ppTRH
gene promoter.
The transcription factor Sp1, initially isolated from HeLa cells, binds
to a GC-rich sequence in the promoter region and activates a wide
variety of cellular genes as well as many viral genes (37, 40).
However, whether Sp1 plays a direct role in any signal transduction
pathways remains to be clarified. In this context, there are some
reports showing an interaction between Sp1 and other transcription
factors for the control of gene expression (45, 46). An interesting
result was reported by Merchant et al., who showed that
stimulation of the gastrin promoter by EGF in GH4 cells was
mediated by Sp1 in conjunction with two additional uncharacterized
transcription factors binding to the overlapping half-sites of the
GC-rich gastrin EGF response element (47). Taken together with these
observations, the present results are interpreted to support the
possibility that an interaction between different sets of transcription
factors and Sp1 is one of the nuclear pathways for the EGF stimulation
of specific genes.
In conclusion, the present results suggest that EGF serves as a
possible stimulator of ppTRH gene expression. EGF or related growth
factors produced locally or from the systemic circulation might be
involved in regulation of the level of hypothalamic TRH mRNA. It is
known that TRH can be produced by anterior pituitary cells (48, 49).
Because the transfection experiments in this study were performed using
a clonal pituitary tumor cell line, it is possible that EGF stimulates
ppTRH gene expression in subsets of cell types also in the pituitary
gland. Further study is required to elucidate the physiological
significance of EGF in the regulation of TRH function in
vivo.
 |
Acknowledgments
|
|---|
We thank Dr. William M. Wood (University of Colorado Health
Sciences Center, Denver, CO) for providing the pA3Luc plasmid.
Received July 21, 1997.
 |
References
|
|---|
-
Jackson IMD 1982 Thyrotropin-releasing
hormone. N Engl J Med 306:145155[Medline]
-
Lechan RM, Wu P, Jackson IMD, Wolfe H, Cooperman S,
Mandel G, Goodman RH 1986 Thyrotropin-releasing hormone precursor:
characterization in rat brain. Science 231:159161[Abstract/Free Full Text]
-
Segerson TP, Kauer J, Wolfe HC, Mobtaker H, Wu P,
Jackson IMD, and Lechan RM 1987 Thyroid hormone regulates TRH
biosynthesis in the paraventricular nucleus of the rat hypothalamus.
Science 238:7880[Abstract/Free Full Text]
-
Koller KJ, Wolff RS, Warden MK, Zoeller RT 1987 Thyroid hormone regulate TRH biosynthesis in the paraventricular
nucleus. Proc Natl Acad Sci USA 84:73297333[Abstract/Free Full Text]
-
Yamada M, Radvick S, Wondisford F, Nakayama Y,
Weintraub BD, Wilber JF 1991 Cloning and structure of human
genomic DNA and hypothalamic cDNA encoding human
preprothyrotropin-releasing hormone. Mol Endocrinol 4:551556[Abstract/Free Full Text]
-
Satoh T, Yamada M, Iwasaki T, Mori M 1996 Negative
regulation of the gene for the preprothyrotropin-releasing hormone from
the mouse by thyroid hormone requires additional factor in conjunction
with thyroid hormone receptor. J Biol Chem 271:2791927926[Abstract/Free Full Text]
-
Feng P, Li QL, Satoh T, Wilber JF 1994 Ligand (T3)
dependent and independent effects of thyroid hormone receptors upon
human TRH gene transcription in neuroblastoma cells. Biochem Biophys
Res Commun 200:171177[CrossRef][Medline]
-
Kakucska I, Qi Y, Lechan RM 1995 Changes in
adrenal status affect hypothalamic thyrotropin-releasing hormone gene
expression in parallel with corticotropin-releasing hormone.
Endocrinology 136:27952802[Abstract]
-
van Haasteren GA, Linkels E, Klootwijk W, van Toor H,
Rondeel JM, Themmen AP, de Jong FH, Valentijin K, Vaudry H, Bauer
K 1995 Starvation induced changes in the hypothalamic content of
prothyrotropin-releasing hormone (proTRH) mRNA and the hypothalamic
release of proTRH-derived peptides: role of the adrenal gland. J
Endocrinol 145:143153[Abstract/Free Full Text]
-
Cohen S 1962 Isolation of a mouse submaxillary
gland protein accelerating incisor eruption and eyelid opening in the
newborn animal. J Biol Chem 237:15551562[Free Full Text]
-
Hernandez-Sotomayor S, Carpenter G 1992 Epidermal
growth factor receptor: elements of intracellular communication. J
Membr Biol 128:8189[Medline]
-
Elsholtz HP, Mangalam HJ, Potter E, Albert VR, Supowit
S, Evans RM, Rosenfeld MG 1986 Two different cis-active
elements transfer the transcriptional effects of both EGF and phorbol
esters. Science 234:15521557[Abstract/Free Full Text]
-
Supowit SC, Potter E, Evans RM, Rosenfeld MG 1984 Polypeptide hormone regulation of gene transcription: specific 5'
genomic sequence are required for epidermal growth factor and phorbol
ester regulation of prolactin gene expression. Proc Natl Acad Sci USA 81:29752979[Abstract/Free Full Text]
-
Altschuler LR, Parist MN, Cageao LF, Chiocchio SR,
Fernandez-Po JA, Zaninovich AA 1993 Epidermal growth factor
stimulates thyrotropin secretion in the rat. Neuroendocrinology 57:2327[Medline]
-
Fan X, Childs GV 1995 Epidermal growth factor and
transforming growth factor-alpha messenger ribonucleic acids and their
receptors in the rat anterior pituitary: localization and regulation.
Endocrinology 136:22842293[Abstract]
-
Arancibia S, Rage F, Astier H, Tapia-Aranchibia L 1996 Neuroendocrine and autonomous mechanisms underlying
thermoregulation in cold environment. Neuroendocrinology 64:257267[Medline]
-
Zoeller RT, Kabeer N, Albers HE 1990 Cold exposure
elevates cellular level of messenger ribonucleic acid encoding
thyrotropin-releasing hormone in paraventricular nucleus despite
elevated levels of thyroid hormones. Endocrinology 127:29552962[Abstract/Free Full Text]
-
Rage F, Lazaro JB, Benyassi A, Aranchibia S,
Tapia-Aranchibia L 1994 Rapid changes in somatostatin and TRH mRNA
in whole rat hypothalamus in response to acute cold exposure. J
Neuroendocriol 6:1923
-
Ma YJ, Berg-von der Emde K, Moholy-Siebert M, Hill DF,
Ojeda SR 1994 Region-specific regulation of transforming growth
factor
(TGF) gene expression in astrocytes of the neuroendocrine
brain. J Neurosci 14:56445651[Abstract]
-
Ma YJ, Hill DF, Junier M, Costa ME, Felder SE, Ojeda
SR 1993 Expression of epidermal growth factor receptor changes in
the hypothalamus during the onset of female puberty. Mol Cell Neurosci 5:246262
-
Luger A, Calogero AE, Kalogeras K, Gallucci WT, Gold PW,
Loriaux DL, Chousos GP 1988 Interaction of epidermal growth factor
with the hypothalamic-pituitary-adrenal axis: potential physiologic
relevance. J Clin Endocrinol Metab 66:334337[Abstract/Free Full Text]
-
Fan X, Nagle GT, Collins, TJ, Childs GV 1995 Differential regulation of epidermal growth factor and transforming
growth factor-alpha messenger ribonucleic acid in the rat anterior
pituitary as well as hypothalamus. Endocrinology 136:873880[Abstract]
-
Ma YJ, Berg-von der Emde K, Rage F, Wetsel WC, Ojeda
SR 1997 Hypothalamic astrocytes respond to transforming growth
factor-
with the secretion of neuroactive substances that stimulate
the release of luteinizing hormone-releasing hormone. Endocrinology 138:1925[Abstract/Free Full Text]
-
Feng P, Gu J, Kim UJ, Wilber J F 1993 Identification, localization, and developmental studies of rat
preprothyrotropin-releasing hormone mRNA in the testis. Neuropeptides 24:6339[CrossRef][Medline]
-
Maxwell IH, Harrison GH, Wood WM, Maxwell F 1989 A
DNA cassette containing a trimerized SV40 polyadenylation signal which
efficiently blocks spurious plasmid-initiated transcription.
Biotechniques 7:276280[Medline]
-
Wood WM, Kao MY, Gordon DF, Ridgway EC 1989 Thyroid
hormone regulates the mouse thyrotropin ß-subunit gene promoter in
transfected primary thyrotropes. J Biol Chem 264:1484014847[Abstract/Free Full Text]
-
Sanger F, Nicklen S, Coulson A 1977 DNA sequencing
with chain-termination inhibitors. Proc Natl Acad Sci USA 74:54635467[Abstract/Free Full Text]
-
Nordeen SK 1988 Luciferase reporter gene vectors
for analysis of promoters and enhancers. Biotechniques 6:702705
-
Ausubel, FM, Brent R, Kingston RE, Moore DD, Seidman JG,
Smith JA, Struhl K 1994 Current Protocols in Molecular Biology.
Greene, New York
-
Bradford M 1976 A rapid and sensitive method for
the quantitation of microgram quantities of protein utilizing the
principle of protein-dye binding. Anal Biochem 72:248[CrossRef][Medline]
-
Andrews NC, Faller DV 1991 A rapid micropreparation
technique for extraction of DNA-binding proteins from limiting numbers
of mammalian cells. Nucleic Acids Res 19:2499[Free Full Text]
-
Plata-Salaman C 1991 Epidermal growth factor and
the nervous system. Peptides 12:653663[CrossRef][Medline]
-
Johnson LK, Baxter JD, Vlodavsky I, Gospodarowics D 1980 Epidermal growth factor and expression of specific genes: effects
on cultured rat pituitary cells are dissociable from mitogenic
response. Proc Natl Acad Sci USA 77:394398[Abstract/Free Full Text]
-
Halpern J, Hinkle PM 1983 Binding and
internalization of epidermal growth factor by rat pituitary tumor
cells. Mol Cell Endocrinol 33:183187[CrossRef][Medline]
-
Yang X, Fyodorov D, Deneris ES 1995 Transcriptional
analysis of acethylcholine receptor
3 gene promoter motifs that bind
Sp1 and AP2. J Biol Chem 270:85148520[Abstract/Free Full Text]
-
Henson JW 1994 Regulation of the glial-specific JC
virus early promoter by the transcription factor Sp1. J Biol Chem 269:10461050[Abstract/Free Full Text]
-
Courey AJ, Tjian R 1992 Mechanism of
transcriptional control as revealed by studies human transcription
factor Sp1. In: McKnight SL, Yamamoto KR (eds) Transcriptional
Regulation. Cold Harbor Laboratory Press, Cold Spring Harbor, pp
743769
-
Kingsley C, Winoto A 1992 Cloning of GT box-binding
protein: a novel Sp1 multigene family regulating T-cell receptor gene
expression. Mol Cell Biol 12:42514261[Abstract/Free Full Text]
-
Hagen G, Muller S, Beat M, Suske G 1992 Cloning by
recognition site screening of two novel GT box binding protein: a
family of Sp1 related genes. Nucleic Acids Res 20:55195525[Abstract/Free Full Text]
-
Kadonaga JT, Carner, KR, Masiarz, FR, Tjian R 1987 Isolation of cDNA encoding transcription factor Sp1 and functional
analysis of the DNA binding domain. Cell 51:10791090[CrossRef][Medline]
-
Kadonaga JT, Jones KA, Tjian R 1986 Promoter-specific activation of RNA polymerase II transcription by Sp1.
Trends Biochem Sci 11:2023
-
Robidoux S, Gosselin P, Harvey M, Leclerc S, Guerin
S 1992 Transcription of the mouse secretory protease inhibitor p12
gene is activated by the developmentally regulated positive
transcription factor Sp1. Mol Cell Biol 12:37963806[Abstract/Free Full Text]
-
Kadonaga JT, Courey AJ, Ladika J, Tjian R 1988 Distinct region of Sp1 modulate DNA binding and transcriptional
activation. Science 24:15661570
-
Shi H, Teng C 1996 Promoter-specific activation of
mouse lactoferrin gene by epidermal growth factor involves two adjacent
regulatory element. Mol Endocrinol 10:732741[Abstract/Free Full Text]
-
Look DC, Pelletier MR, Tidwell RM, Roswit WT, Holtzman
MJ 1995 Stat1 depends on transcriptional synergy with Sp1. J
Biol Chem 270:3026430267[Abstract/Free Full Text]
-
Wu RL, Chen TT, Sun TT 1994 Functional importance
of an Sp-1 and an NF
B-related nuclear protein in a
keratinocyte-specific promoter of rabbit K3 keratin gene. J Biol
Chem 269:2845028459[Abstract/Free Full Text]
-
Merchant JL, Shiotani A, Mortensen ER, Shumaker DK 1995 Epidermal growth factor stimulation of the human gastrin promoter
requires Sp1. J Biol Chem 270:63146319[Abstract/Free Full Text]
-
Childs GV, Cole DE, Kubek M, Tobin RB, Wilber JF 1978 Endogenous thyrotropin-releasing hormone in the anterior
pituitary: sites of activity as identified by immunocytochemical
staining. J Histochem Cytochem 26:901908[Abstract]
-
Bruhn TO, Bolduc TG, Maclean DB, Jackson IMD 1991 ProTRH peptides are synthesized and secreted by anterior pituitary
cells in long-term culture. Endocrinology 129:556558[Abstract/Free Full Text]
This article has been cited by other articles:

|
 |

|
 |
 
K. Hashimoto, E. Ishida, S. Matsumoto, S. Okada, M. Yamada, T. Satoh, T. Monden, and M. Mori
Carbohydrate Response Element Binding Protein Gene Expression Is Positively Regulated by Thyroid Hormone
Endocrinology,
July 1, 2009;
150(7):
3417 - 3424.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
S. Matsumoto, K. Hashimoto, M. Yamada, T. Satoh, J. Hirato, and M. Mori
Liver X Receptor-{alpha} Regulates Proopiomelanocortin (POMC) Gene Transcription in the Pituitary
Mol. Endocrinol.,
January 1, 2009;
23(1):
47 - 60.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
M. D. Kaeser, A. Aslanian, M.-Q. Dong, J. R. Yates III, and B. M. Emerson
BRD7, a Novel PBAF-specific SWI/SNF Subunit, Is Required for Target Gene Activation and Repression in Embryonic Stem Cells
J. Biol. Chem.,
November 21, 2008;
283(47):
32254 - 32263.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
K. Hashimoto, S. Matsumoto, M. Yamada, T. Satoh, and M. Mori
Liver X Receptor-{alpha} Gene Expression Is Positively Regulated by Thyroid Hormone
Endocrinology,
October 1, 2007;
148(10):
4667 - 4675.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
K. Hashimoto, M. Yamada, S. Matsumoto, T. Monden, T. Satoh, and M. Mori
Mouse Sterol Response Element Binding Protein-1c Gene Expression Is Negatively Regulated by Thyroid Hormone
Endocrinology,
September 1, 2006;
147(9):
4292 - 4302.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
A Blondet, J Gout, P Durand, M Begeot, and D Naville
Expression of the human melanocortin-4 receptor gene is controlled by several members of the Sp transcription factor family
J. Mol. Endocrinol.,
April 1, 2005;
34(2):
317 - 329.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
P. Joseph-Bravo
Hypophysiotropic Thyrotropin-Releasing Hormone Neurons as Transducers of Energy Homeostasis
Endocrinology,
November 1, 2004;
145(11):
4813 - 4815.
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
G. Wang, A. B. Leiter, E. W. Englander, and G. H. Greeley Jr.
Insulin-Like Growth Factor I Increases Rat Peptide YY Promoter Activity through Sp1 Binding Sites
Endocrinology,
February 1, 2004;
145(2):
659 - 666.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
H. Xu, M. Inouye, E. R. Hines, J. F. Collins, and F. K. Ghishan
Transcriptional regulation of the human NaPi-IIb cotransporter by EGF in Caco-2 cells involves c-myb
Am J Physiol Cell Physiol,
May 1, 2003;
284(5):
C1262 - C1271.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
A. Ozawa, M. Yamada, T. Satoh, T. Monden, K. Hashimoto, H. Kohga, Y. Hashiba, T. Sasaki, and M. Mori
Transcriptional Regulation of the Human PRL-Releasing Peptide (PrRP) Receptor Gene by a Dopamine 2 Receptor Agonist: Cloning and Characterization of the Human PrRP Receptor Gene and Its Promoter Region
Mol. Endocrinol.,
April 1, 2002;
16(4):
785 - 798.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
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]
|
 |
|

|
 |

|
 |
 
H. Xu, J. F. Collins, L. Bai, P. R. Kiela, R. M. Lynch, and F. K. Ghishan
Epidermal growth factor regulation of rat NHE2 gene expression
Am J Physiol Cell Physiol,
August 1, 2001;
281(2):
C504 - C513.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
H. Xu, J. F. Collins, L. Bai, P. R. Kiela, and F. K. Ghishan
Regulation of the human sodium-phosphate cotransporter NaPi-IIb gene promoter by epidermal growth factor
Am J Physiol Cell Physiol,
March 1, 2001;
280(3):
C628 - C636.
[Abstract]
[Full Text]
[PDF]
|
 |
|

|
 |

|
 |
 
T. Satoh, T. Ishizuka, T. Monden, N. Shibusawa, T. Hashida, M. Kishi, M. Yamada, and M. Mori
Regulation of the Mouse Preprothyrotropin-Releasing Hormone Gene by Retinoic Acid Receptor
Endocrinology,
November 1, 1999;
140(11):
5004 - 5013.
[Abstract]
[Full Text]
|
 |
|