Inhibition of Cyclooxygenase-2 Gene Expression by p53*
Kotha
Subbaramaiah
§¶,
Nasser
Altorki¶
,
Wen
Jing
Chung
¶,
Juan R.
Mestre¶**
,
Anu
Sampat
, and
Andrew J.
Dannenberg
§¶§§
From the Departments of
Medicine,
§ Surgery, and
Cardiothoracic Surgery, The New York
Presbyterian Hospital-Cornell, ** Head and Neck Service, Department of
Surgery, Memorial Sloan-Kettering Cancer Center, and ¶ Strang
Cancer Prevention Center, New York, New York 10021
 |
ABSTRACT |
Oncogenes enhance the expression of
cyclooxygenase (Cox)-2, but interactions between tumor suppressor genes
and Cox-2 have not been studied. In the present work, we have compared
the levels of Cox-2 and the production of prostaglandin
E2 in mouse embryo fibroblasts that do not express
any p53 ((10)1) versus the same cell line ((10.1)Val5)
engineered to overexpress wild-type (wt) p53 at 32 °C or
mutant p53 at 39 °C. Cells expressing wt p53 showed about a 10-fold
decrease in synthesis of prostaglandin E2 compared with those expressing mutant p53. Levels of Cox-2 protein and mRNA
were markedly suppressed by wt p53 but not by mutant p53. Nuclear
run-offs revealed decreased rates of Cox-2 transcription in
cells expressing wt p53. The activity of the Cox-2 promoter was reduced by 85% in cells expressing wt p53 but was reduced only by
30% in cells expressing mutant p53 compared with cells null for p53.
The effect of p53 on the suppression of Cox-2 promoter activity was localized to the first 40 base pairs 5' from the transcription start site. Electrophoretic mobility shift assay revealed
that p53 competed with TATA-binding protein for binding to mouse
Cox-2 or human Cox-2 promoter extending from
50 to +52 base pairs. The results of this study suggest that
interactions between p53 and Cox-2 could be important for understanding
why levels of Cox-2 are undetectable in normal cells and increased in
many tumors.
 |
INTRODUCTION |
Two different isoforms of cyclooxygenase
(Cox)1 catalyze the synthesis
of prostaglandins from arachidonic acid. Cox-1 is a constitutive
enzyme, whereas Cox-2 is inducible (1, 2). The Cox-2 gene is
an early response gene that is rapidly induced by phorbol esters,
cytokines, growth factors, and carcinogens (3-7). The different
responses of the genes encoding Cox-1 and Cox-2
reflect, at least in part, differences in the regulatory elements in
the 5'-flanking regions of the two genes (8).
Numerous studies support the idea that Cox-2 is important in
carcinogenesis. It is known, for example, that Cox-2 is up-regulated in
transformed cells and in various forms of cancer (9-16). A null
mutation for Cox-2 markedly reduces the number and size of intestinal tumors in a murine model of familial adenomatous polyposis, i.e. APC
716 knockout mice (17).
Cox-2 deficiency also protects against the formation of
extraintestinal tumors. Thus, Cox-2 knockout mice developed
about 75% fewer chemically induced skin papillomas than control mice
(18), and a selective inhibitor of Cox-2 caused a nearly complete
suppression of azoxymethane-induced colon cancer (19). It is also known
that the expression of Cox-2 is enhanced by oncogenes (9-11), but the
effects of tumor suppressor genes, e.g. p53, on Cox-2 are unstudied.
p53 is important in the suppression of cellular growth and
transformation (20-24). In addition, induction of wild-type (wt) p53
can cause cells to undergo apoptosis (25, 26). By contrast, inactivation of p53 can lead to deregulation of the cell cycle and DNA
replication, selective growth advantage, and tumor formation (27, 28).
Significantly, p53 can either increase or suppress the expression of a
number of target genes (29-32). Gene activation usually involves
binding of p53 to specific consensus sequences. Recent studies indicate
that repression of transcription by p53 may involve interaction with
basal transcription machinery and may be important in mediating
programmed cell death (33-36).
In the present work, we have investigated the effects of p53 on
Cox-2 gene expression. Our data show that wt p53 causes a marked decrease in the expression of Cox-2. In contrast, mutant p53 did
not cause a significant reduction in levels of Cox-2. Interactions
between p53 and Cox-2 could be important for understanding why levels
of Cox-2 are essentially undetectable in normal epithelial cells and
elevated in many cancers.
 |
EXPERIMENTAL PROCEDURES |
Materials--
Dulbecco's modified Eagle's medium, fetal
bovine serum, and calcium phosphate transfection kits were from Life
Technologies, Inc. Sodium arachidonate and
poly(deoxyinosinic-deoxycytidylic acid) were from Sigma. Enzyme
immunoassay reagents for PGE2 assays were from Cayman Co.
(Ann Arbor, MI). Random priming kits were from Boehringer Mannheim.
Nitrocellulose membranes were from Schleicher & Schuell.
[32P]ATP, [32P]CTP, and
[32P]UTP were obtained from DuPont New England Nuclear
(Boston, MA). Reagents for the luciferase assay were from Analytical
Luminescence (San Diego, CA). RNA was prepared using an isolation kit
from QIAGEN Inc. (Chatsworth, CA). Plasmid DNA isolation kits and
recombinant TATA-binding protein (TBP) were purchased from Promega
(Madison, WI). Goat polyclonal anti-Cox-2 and anti-Cox-1 antisera were
from Santa Cruz Biotechnology, Inc. (Santa Cruz, CA). Western blotting detection reagents were from Amersham. Oligonucleotides were
synthesized by Genosys Biotechnologies Inc. (The Woodlands, TX).
GST-agarose was purchased from Pharmacia Biotech Inc. T4 polynucleotide
kinase was purchased from New England Biolabs, Inc. (Beverly, MA).
Proteinase K, RNase-free DNase, and RNase A for nuclear run-offs and 18 S rRNA cDNA were from Ambion Inc. (Austin, TX).
Cell Lines--
The murine embryo fibroblast-derived cell lines
(10)1 and (10.1)Val5 were obtained from Dr. Arnold Levine (Princeton
University, Princeton, NJ). The (10.1)Val5 cell line was generated by
stable transfection of parental cell line (10)1, which contains no endogenous p53, with the temperature-sensitive p53 allele encoding valine at amino acid 135 (37, 38). The (10.1)Val5 line contains a
temperature-sensitive p53 mutant that is wt at 32 °C and mutant at
39 °C (38).
PGE2 Production--
(10)1 and (10.1)Val5 cell lines
were plated in 6-well plates and grown in Dulbecco's modified Eagle's
medium containing 10% fetal bovine serum at 37 °C until they were
approximately 40% confluent. The cell lines were then shifted to
32 °C or to 39 °C for 18 h. The medium was then replaced
with fresh medium containing 10 µM sodium arachidonate.
30 min later, the medium was collected to measure the synthesis of
PGE2. The levels of PGE2 released by the cells
were measured by enzyme immunoassay (9). Levels of PGE2
production were normalized to protein concentrations.
Western Blotting--
Cell lysates were prepared as described
previously (39). SDS-polyacrylamide gel electrophoresis was performed
under reducing conditions on 10% polyacrylamide gels as described by
Laemmli (40). The resolved proteins were transferred onto
nitrocellulose sheets as detailed by Towbin et al. (41). The
nitrocellulose membrane was then incubated with a goat polyclonal
anti-Cox-2 antiserum or a polyclonal anti-Cox-1 antiserum. A secondary
antibody to IgG conjugated to horseradish peroxidase was used. The
blots were probed with the ECL Western blot detection system according to the manufacturer's instructions.
Northern Blotting--
Total cellular RNA was isolated from cell
monolayers using a RNA isolation kit from QIAGEN Inc. For Northern
blots, 10 µg of total cellular RNA per lane were electrophoresed in
formaldehyde-containing 1.2% agarose gels and transferred to
nylon-supported membranes. After baking, membranes were prehybridized
for 8 h and then hybridized in a solution containing 50%
formamide, 5× SSPE, 5× Denhardt's solution, 0.1% SDS, and 100 µg/ml single-stranded salmon sperm DNA. Hybridization was carried out
for 16 h at 42 °C with radiolabeled murine Cox-2 and 18 S rRNA
probes. After hybridization, the membrane was washed for 20 min at room
temperature in 2× SSPE and 0.1% SDS, washed twice for 20 min in the
same solution at 55 °C, and washed twice for 20 min in 0.1× SSPE
and 0.1% SDS at 55 °C. Washed membranes were then subjected to
autoradiography. The density of the bands was quantified by densitometry.
Nuclear Run-off--
For each cell line, 2.5 × 105 cells were plated in four T150 dishes and grown in
Dulbecco's modified Eagle's medium containing 10% fetal bovine serum
until they were approximately 50% confluent at 37 °C. The cell
lines were then shifted to 32 °C for 18 h. Nuclei were isolated
and stored in liquid nitrogen. For the transcription assay, nuclei
(1.0 × 107) were thawed and incubated in reaction
buffer (10 mM Tris, pH 8, 5 mM
MgCl2, and 0.3 M KCl) containing 100 µCi of
[
-32P]UTP and 1 mM unlabeled nucleotides.
After 30 min, labeled nascent RNA transcripts were isolated. The Cox-2
(TIS10) and 18 S rRNA cDNAs were immobilized onto nitrocellulose
and prehybridized overnight in hybridization buffer. Hybridization was
carried out at 42 °C for 24 h using at least 5 × 105 cpm of labeled nascent RNA transcripts for each
treatment group. The membranes were washed twice with 2× SSC buffer
for 1 h at 55 °C and then treated with 10 mg/ml RNase A in 2×
SSC at 37 °C for 30 min, dried, and autoradiographed.
Plasmids--
Cox-2 cDNA and Cox-2 promoter
deletion constructs (TIS10L, TIS-300, TIS-180, TIS-80, and TIS-40) were
generously provided by Dr. Harvey Herschman (University of California,
Los Angeles, CA). The wild-type p53 (pC53-SN3) expression vector was
kindly provided by Dr. Arnold Levine. The plasmid construct GST.p53 was a generous gift of Dr. Derek LeRoith (National Institutes of Health, Bethesda, MD) (34). The v-src expression vector was a gift from Dr.
David Foster (Hunter College, New York, NY).
Transient Transfection Assays--
Cells were seeded at a
density of 5 × 104 cells/well in 6-well dishes and
grown to 30-40% confluence at 37 °C in Dulbecco's modified
Eagle's medium containing 10% fetal bovine serum, unless stated
otherwise. For each well, 2 µg of plasmid DNA were transfected into
cells using the calcium phosphate precipitation method according to the
manufacturer's instructions. After 16 h, the medium was changed,
and cells were then shifted to 32 °C or 39 °C. At the end of the
treatment period, cells were harvested, and luciferase activity was
measured. Each well was washed twice with phosphate-buffered saline.
100 µl of 1× lysis buffer (Analytical Luminescence Laboratories, San
Diego, CA) were added to each well for 15 min. The lysate was
centrifuged for 1 min at 4 °C. The supernatant was used to assay
luciferase activity with a Monolight 2010 Luminometer (Analytical Luminescence Laboratories) according to the manufacturer's
instructions. Luciferase activity is expressed per microgram of protein
in the cell extract.
Preparation of GST.p53--
Purified p53 protein was prepared as
a GST fusion protein according to methods described previously
(34).
Gel Shift Assays--
A fragment of the human COX-2
or mouse Cox-2 promoter extending from
50 to +52
encompassing the in vivo transcription initiation site was
made by polymerase chain reaction amplification. After purification
from agarose gels, the fragment was dephosphorylated using calf
intestinal phosphatase and end-labeled with [
-32P]ATP
using T4 polynucleotide kinase. The labeled probe was separated from
unincorporated nucleotides using purification columns from QIAGEN Inc.
Gel shift assays were performed by preincubating TBP (1 f.p.u./reaction), GST.p53 (100 ng), or a combination of both proteins in 9 µl of 20 mM Hepes (pH 7.5), 70 mM KCL,
12% glycerol, 0.05% Nonidet P-40, 100 µM
ZnSO4, 0.05 M dithiothreitol, 1 mg/ml bovine serum albumin, and 0.1 mg/ml poly(deoxyinosinic-deoxycytidylic acid) on
ice. After 15 min, 100 pg of the labeled fragment were added, and the
reaction was incubated for an additional 10 min at 25 °C. Changes in
mobility were assessed by electrophoresis through a 5% polyacrylamide
gel that was run at 250 V for 2 h. After fixation, the gel was autoradiographed.
Statistics--
Comparisons between groups were made by the
Student's t test. A difference between groups of
p < 0.05 was considered significant.
 |
RESULTS |
Wild-Type p53 Inhibits the Synthesis of Prostaglandins and
Expression of Cox-2--
The data in Fig.
1 show that cells containing wt p53
synthesized about 90% less PGE2 than cells that are null
for p53. By contrast, mutant p53 did not inhibit production of
PGE2. To evaluate whether the inhibition of prostaglandin
synthesis could be related to differences in the levels of Cox, Western
blotting of the cell lysate protein was carried out. Fig.
2 shows that wt p53 caused a nearly
complete suppression of Cox-2 expression, whereas mutant p53 did not
affect the levels of Cox-2. In other experiments, the suppressive
effects of wt p53 on amounts of COX-2 protein were more modest. Cox-1
was not detectable by Western blotting in any of the cells tested. To
further elucidate the mechanism responsible for the changes in the
amount of Cox-2 protein, we determined the steady-state levels of Cox-2
mRNA by Northern blotting. Levels of Cox-2 mRNA were reduced in
the presence of wt p53 but not mutant p53 (Fig.
3).

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Fig. 1.
Wild-type but not mutant p53 down-regulates
the production of PGE2 in mouse embryo fibroblasts.
(10)1 and (10.1)Val5 cells were grown at 32 °C and 39 °C for
18 h. (10)1 cells contain no p53 protein. (10.1)Val5 cells express
predominantly wt p53 at 32 °C but express mutant p53 at 39 °C.
The medium was then replaced with fresh medium containing 10 µM sodium arachidonate. 30 min later, the medium was
collected to determine the levels of PGE2. Production of
PGE2 was determined by enzyme immunoassay.
Columns, means; bars, S.D.; n = 6; *, p < 0.01 compared with (10)1 cells.
|
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Fig. 2.
Levels of Cox-2 protein are decreased in
cells expressing wild-type but not mutant p53. (10)1 and
(10.1)Val5 cells grown at 37 °C were shifted to 32 °C or 39 °C
for 18 h. Cellular lysate protein (25 µg/lane) was loaded onto a
10% SDS-polyacrylamide gel, electrophoresed, and subsequently
transferred onto nitrocellulose. Immunoblots were probed with an
antibody specific for Cox-2. Lane 1, ovine Cox-2 standard;
lane 2, (10)1 cells at 32 °C; lane 3,
(10.1)Val5 cells at 32 °C; lane 4, (10)1 cells at
39 °C; lane 5, (10.1)Val5 cells at 39 °C.
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Fig. 3.
Expression of wt p53 decreases the
steady-state level of Cox-2 mRNA. (10)1 and (10.1)Val5 cells
were grown at 37 °C before being shifted to either 32 °C or
39 °C for 18 h. Total cellular RNA was isolated. Each lane
contained 10 µg of RNA. The Northern blot was hybridized with probes
that recognized Cox-2 mRNA and 18 S rRNA. Results of densitometry
are expressed in a.u. Lane 1, (10.1)Val5 cells at 32 °C,
81 a.u.; lane 2, (10)1 cells at 32 °C, 206 a.u.; lane 3, (10.1)Val5 cells at 39 °C, 218 a.u.;
lane 4, (10)1 cells at 39 °C, 216 a.u.
|
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Cox-2 Transcription Is Suppressed by Wild-Type p53--
Because
differences in the levels of mRNA could reflect altered rates of
transcription or changes in the stability of mRNA, nuclear run-offs
were performed to distinguish between these possibilities. As shown in
Fig. 4, we found lower rates of synthesis
of nascent Cox-2 mRNA in cells expressing wt p53.

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Fig. 4.
Wild-type p53 suppresses the transcription of
Cox-2. (10)1 and (10.1)Val5 cells grown at 37 °C were shifted
to 32 °C for 18 h. Nuclei were isolated. Nuclear run-offs were
performed as described under "Experimental Procedures." The Cox-2
and 18 S rRNA cDNAs were immobilized on nitrocellulose membranes
and hybridized with labeled nascent RNA transcripts. Lane 1,
(10)1 cells; lane 2, (10.1)Val5 cells.
|
|
To further investigate the importance of p53 in modulating the
expression of Cox-2, transient transfections were performed using a murine Cox-2 promoter luciferase construct. The
activity of the Cox-2 promoter was reduced by about 85% in
the cell line expressing wt p53 compared with the p53-null cell line
(Fig. 5). In contrast, mutant p53 caused
about a 30% decrease in Cox-2 promoter activity (Fig. 5).
We also investigated whether p53 could inhibit v-src-mediated induction
of Cox-2 promoter activity. As shown in Fig.
6, overexpressing v-src caused about a
6-fold increase in Cox-2 promoter activity in the p53-null
cell line. The stimulatory effects of v-src were blocked by
overexpressing wt p53 in the same cell system. In separate experiments,
wt p53 also blocked phorbol ester-mediated induction of
Cox-2 promoter activity (data not shown).

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Fig. 5.
Endogenous p53 down-regulates Cox-2 promoter
activity in mouse embryo fibroblasts. (10)1 and (10.1)Val5 cells
were transfected with 2 µg of murine Cox-2 luciferase
construct (TIS10L) containing 963 bases 5' of the Cox-2
transcription start site. After transfection, the cells were grown at
37 °C before being shifted to either 32 °C or 39 °C for
18 h. Six wells were used for each transfection condition.
Columns, means; bars, S.D. *, p < 0.01 compared with (10)1 cells.
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Fig. 6.
Wild-type p53 suppresses v-src-mediated
induction of Cox-2 promoter activity. (10)1 cells, which are null
for p53, were grown under serum-free conditions. Cells were transfected
with 1.0 µg of Cox-2 luciferase construct TIS10L (963 bp)
alone ( p53, ) or with 0.5 µg of expression vector for
wt p53 (+p53, ). Cells were also co-transfected with 1.0 µg of TIS10L plus 0.5 µg of expression vector for v-src
( p53, ) or 1.0 µg of TIS10L plus 0.5 µg of
expression vectors for v-src and wt p53 (+p53, ). The
total amount of DNA was kept constant at 2 µg by using empty vector
DNA. Twenty four h later, luciferase activity was measured. Six wells
were used for each transfection condition. Columns, means;
bars, S.D.
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Localization of the Promoter Region Responsible for Repression of
Transcription--
We next attempted to define the region of the
Cox-2 promoter that responded to p53. This was accomplished
using a series of murine Cox-2 promoter deletion constructs.
As shown in Fig. 7, Cox-2
promoter activity decreased as the length of the promoter decreased.
However, with all promoter constructs including TIS10-40, the activity
of the Cox-2 promoter was higher in the p53-null cell line
compared with the cell line expressing wt p53. The fact that these
differences in promoter activity were maintained despite changes in
promoter length indicates that the suppression of Cox-2 promoter activity by p53 was localized to the first 40 bp 5' of the
transcription start site.

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Fig. 7.
Suppression of Cox-2 promoter activity by p53
is localized to the first 40 bases 5' of the transcription start
site. (10)1 and (10.1)Val5 cells were transfected with 2 µg of a
series of Cox-2 promoter-luciferase deletion constructs:
TIS10L ( 963), TIS10-300, TIS10-180, TIS10-80, and TIS10-40. After
transfection, the cells were shifted from 37 °C to 32 °C for
18 h to induce wt p53 in the (10.1)Val5 cell line. Six wells were
used for each transfection condition. Columns, means;
bars, S.D. *, p < 0.01 compared with (10)1
cells.
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TBP is essential for the transcription of TATA-containing promoters
such as the Cox-2 promoter. p53 has been reported to inhibit gene expression via interactions with TBP (33-35). To study possible interactions between p53 and TBP in the regulation of Cox-2
promoter activity, gel retardation assays were performed. In these
experiments, we used a series of labeled 100-bp fragments of murine and
human Cox-2 promoter spanning from
400 to +52 bp together
with a GST.p53 fusion protein or purified TBP, or both. We did not
observe binding of GST.p53 or TBP to regions of the Cox-2
promoter spanning from
400 to +52 (data not shown). Binding was only
observed with a DNA fragment (from
50 to +52) that included the TATA
box (Fig. 8). Incubation of TBP or
GST.p53 with the labeled probe led to two different retarded bands.
Moreover, the formation of the TBP-DNA complexes was inhibited by the
addition of increasing amounts of GST.p53. We did not observe the
formation of complexes with purified GST alone (data not shown).

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Fig. 8.
p53 competes with TBP for binding to the
Cox-2 promoter. Gel shift analysis was performed using a fragment
of (A) murine Cox-2 or (B) human
Cox-2 promoter extending from 50 to +52 bp. The promoter
fragments were end-labeled with [ -32P]ATP and used in
binding reactions with GST.p53, TBP (1 f.p.u.), or both proteins.
A and B: lane 1, probe;
lane 2, GST.p53 (100 ng); lane 3, TBP; lane
4, TBP and GST.p53 (250 ng); lane 5, TBP and
GST.p53 (200 ng); lane 6, TBP and GST.p53 (150 ng);
lane 7, TBP and GST.p53 (100 ng).
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 |
DISCUSSION |
The present data show that the expression of Cox-2 is markedly
repressed by wt p53 but not by mutant p53. This observation is
important for several reasons. For example, suppression of Cox-2
expression by wt p53 can explain why levels of Cox-2 protein are
undetectable in normal epithelial cells and, by contrast, why mutations
of p53 may contribute to the increased expression of Cox-2 that is
observed in malignant tissues (12-16). Possibly, the induction of
Cox-2 by oncogenes (9, 11), growth factors (42), and cytokines (6) may
be enhanced in cells expressing mutant p53. Moreover, increased
expression of Cox-2 after the mutation of p53 could be an important
link in the relationship between the function of p53 and cancer. Thus,
the products of Cox-2 activity, i.e. prostaglandins,
stimulate cell proliferation (43), inhibit immune surveillance (44,
45), increase the invasiveness of malignant cells (46), and enhance the
production of vascular endothelial growth factor, which promotes
angiogenesis (47). It is already known that transduction of cancer
cells with wt p53 decreases the synthesis of vascular endothelial
growth factor and inhibits tumor cell-induced angiogenesis (48).
Therefore, the present data provide a possible mechanistic explanation
for the regulation of expression of vascular endothelial growth factor and angiogenesis by p53. It thus becomes important to determine the
correlation between the expression of mutant forms of p53 and amounts
of Cox-2 in malignant tissue. It will also be important to determine
whether inactivation or loss of other tumor suppressor genes alters the
expression of Cox-2.
The repression of transcription by p53 is believed to be important for
p53-mediated apoptosis, but the mechanism underlying this effect is not
understood (36). On the other hand, overexpression of Cox-2 in
intestinal epithelial cells inhibits apoptosis (49). Because Cox-2
interacts directly with nucleobindin, which is an apoptosis-associated
protein, Cox-2 might inhibit apoptosis by sequestering nucleobindin
(50). The effects of Cox-2 on apoptosis might also be indirect via the
modulation of levels of intracellular arachidonic acid as suggested by
Chan et al. (51). Levels of arachidonic acid, in turn,
regulate the production of ceramide (52), which can induce apoptosis.
Independent of the exact mechanism, the finding that wt p53
down-regulates the transcription of Cox-2 could be important
for understanding p53-mediated apoptosis.
p53 suppresses a variety of promoters that contain TATA elements (30,
33, 35). This suppression is thought to occur through direct
interaction with components of the basal transcription machinery, such
as TBP. For example, in prior studies, p53 inhibited the binding of TBP
to several promoters, most probably through protein-protein
interactions (33-35, 53). Consequently, TBP is no longer able to
assemble a functional transcription initiation complex. In the current
study, p53 inhibited the formation of complexes between TBP and the
murine and human Cox-2 promoters in a cell-free system. One
possible explanation for this result is a direct competition between
p53 and TBP for the TATA binding site. Interactions between TBP and p53
could decrease the rate of Cox-2 transcription, but this
needs to be confirmed in intact cells.
 |
ACKNOWLEDGEMENTS |
We thank Drs. David Zakim and Babette
Weksler for reviewing the manuscript.
 |
FOOTNOTES |
*
This work was supported in part by National Institutes of
Health Grant CA68136 and the James E. Olson Memorial Fund.The costs of publication of this
article were defrayed in part by the
payment of page charges. The article
must therefore be hereby marked
"advertisement" in
accordance with 18 U.S.C. Section
1734 solely to indicate this fact.

Supported by a Fellowship from the Cancer Research Foundation
of America.
§§
To whom correspondence should be addressed: New York Presbyterian
Hospital-Cornell, Division of Gastroenterology, Room F-231, 1300 York
Ave., New York, NY 10021. Tel.: 212-746-4403; Fax: 212-746-8447; E-mail: ajdannen{at}mail.med.cornell.edu.
 |
ABBREVIATIONS |
The abbreviations used are:
Cox, cyclooxygenase;
bp, base pair(s);
f.p.u., foot print unit;
GST, glutathione
S-transferase;
PGE2, prostaglandin
E2;
TBP, TATA-binding protein;
wt, wild-type;
SSPE, saline-sodium phosphate-EDTA buffer; a.u. arbitrary unit..
 |
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