| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
Molecular Biology and Genetics |
Oral and Pharyngeal Cancer Branch, National Institute of Dental and Craniofacial Research, NIH, Bethesda, Maryland 20892-4330 [R. S-P., J. M. R., J. S. G.], and National Cancer Center Research Institute, Tokyo 104, Japan [Y. T.]
 |
ABSTRACT |
|---|
 Top ABSTRACT INTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
|
INTRODUCTION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
In addition, genotoxic stress stimulates the activity of a family of
protein kinases closely related to
MAPKs4
termed stress-activated protein kinases, which includes JNK and p38
family members. Perhaps the most studied members among them have been
the JNKs, which can be potently activated by genotoxic stress induced
by UV, 
-radiation, and chemotherapeutic drugs (14)
. Of
interest, it has been recently shown that JNK is able to phosphorylate
p53 (15)
, thereby enhancing its protein stability
(16
, 17)
. However, there is no clear evidence with regard
to whether JNK is the only mediator of p53 activation in response to
genotoxic stress (1)
. Moreover, recently available reports
suggest that JNK and p53 are independently activated by genotoxic
stress (18)
and that JNK activation does not always lead
to an increase in the activity of p53 (19)
. Thus, although
JNK may play an important role in the regulation of p53 stability,
these observations raised the possibility that additional signaling
molecules may participate in the enhanced transcriptional activity of
p53 in response to genotoxic stress.
In this study, we found that p38 plays a key role in the activation of
p53 by genotoxic stress when provoked by DNA-damaging chemotherapeutic
agents. We demonstrate that in NIH 3T3 cells, p38 can be potently
activated by drugs that cause DNA damage by either promoting the
formation of DNA adducts or inhibiting topoisomerase II, but not by
therapeutically relevant doses of -radiation, and that the blockade
of p38 by chemical inhibitors prevent the transcriptional activation of
p53 by these anticancer drugs. This effect was found not to be related
to changes in the amount or localization of the p53 protein. Instead,
we found that p38 phosphorylates p53 in its
NH2-terminal transactivating domain at serine 33,
one of the residues previously described to be phosphorylated in
response to DNA damage. We also found that activation of p38 by
upstream molecules is sufficient to stimulate p53 and that this
response requires the phosphorylation of p53 in serine 33. Moreover, we
observed that the blockade of p38 diminishes the apoptotic response to
anticancer agents, thus increasing the survival of the treated cells.
Taken together, these findings suggest a critical role for p38 in p53
activation through the phosphorylation of an
NH2-terminal regulatory residue, serine 33, and
in the apoptotic response to genotoxic stress when elicited by
chemotherapeutic agents.
|
MATERIALS AND METHODS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
-irradiation and UV irradiation, we
used a gamma cell (dose rate, 2.5 Gy/min) and a stratalinker
(Stratagene).
Cell Lines.
NIH 3T3 fibroblasts were maintained in DMEM (Life Technologies, Inc.)
supplemented with 10% calf serum. 293T and Saos-2 cells were
maintained in DMEM supplemented with 10% fetal bovine serum.
Reporter Gene Assays.
NIH 3T3 cells and Saos-2 cells were transfected in triplicates either
by the calcium-phosphate precipitation technique or with LipofectAMINE
(Life Technologies, Inc.), with the indicated expression and reporter
plasmids, together with pCDNAIII ß-gal as a control for transfection
efficiency. After 24 h, cells were left untreated or treated with
either DOX or CDDP for the indicated times and doses in the presence or
absence of p38 inhibitors, which were added 40 min before drug or
physical treatment. Cells were then lysed using reporter lysis buffer
(Promega) and processed for CAT, luciferase, and ß-gal activity, as
reported previously (20)
. CAT and luciferase activity were
normalized by the ß-gal activity in each sample and expressed as the
fold increase with respect to control cells.
Kinase Assays.
Cells were transfected by LipofectAMINE Plus Reagent according to
the manufacturer’s instructions (Life Technologies, Inc.) with the
different expression plasmids. The phosphorylating activity of an
epitope-tagged p38
MAPK or its mutant, T106M, was assessed as
described previously (20)
, using 1.5 µg/µl myelin
basic protein (Sigma) or 5 µg of purified, bacterially expressed
GST-p53 fusion proteins as substrates, as indicated. Samples were
analyzed by SDS-gel electrophoresis on acrylamide gels, and
autoradiography was performed with the aid of an intensifying
screen.
Western Blot Analysis and Antibodies.
Cells were analyzed by Western blotting after SDS-PAGE using
different antibodies. Rabbit polyclonal antisera to phospho-p38 protein
was purchased from New England Biolabs, and anti-p38 and
p21WAF serums were from Santa Cruz Biotechnology.
Monoclonal antibodies against p53 were from Oncogene Science (Ab-1) or
Chemicon (UCN-1), the anti-6-His tag was from Sigma, and the anti-HA
tag was from Babco (clone HA 11). Phospho-specific purified antibody to
serine 33 of p53 has been described previously (21)
. All
antibodies were used according to the manufacturer’s instructions.
Immunocomplexes were visualized by enhanced chemiluminescence detection
(Amersham Corp.) using goat antimouse IgGs or antirabbit IgGs coupled
to horseradish peroxidase as secondary antibodies (Cappel).
Immunofluorescence.
NIH 3T3 cells were treated with different stimuli for the indicated
times, washed twice with PBS, fixed with 4% formaldehyde and 5%
sucrose in PBS for 10 min, and permeabilized with 0.5% Triton X-100 in
PBS for 10 min. The cells were incubated with Ab-1 anti-p53 antibody
(Oncogene Science) for 2 h, washed three times with PBS, and then
incubated with a 1:100 dilution of fluorescein-conjugated goat
F(ab')2 IgG antimouse antibody (Jackson
ImmunoResearch Laboratories, Inc.). Coverslips were mounted in
Gel-mount (Biomeda Corp., Foster City, CA) and then examined using a
Carl-Zeiss Confocal microscope.
Plasmids.
pG13 CAT, pG13 Luc, and pCMVp53 were kindly supplied by B. Vogelstein
(Howard Hughes Medical Institute, The Johns Hopkins University,
Baltimore, MD). p38 tagged with HA and MKK6 has been
described previously (20)
. HA-p38 in the expression vector
pCEFL was used as a template to generate a mutant p38 in which
Thr106 was changed to Met using
oligonucleotides by the PCR overlapping extension technique. The PCR
product was then cloned into pCEFL as a HA tag. GST-fusion
proteins including the NH2-terminal 86 or 126
amino acids of p53 were generated by subcloning the corresponding
coding region amplified by PCR from pCMVp53 into the pGEX expression
vector (Pharmacia). GST-p53 1–86(1–86) mutants in residues 15, 33, and 46
were generated using specific primers in which serine or threonine was
substituted for alanine, using the Quickchange site-directed
mutagenesis kit (Stratagene). Bacterially expressed proteins were
purified using standard techniques. Expression plasmids for 6
His-tagged p53 were generated by subcloning the coding region of p53
obtained by PCR amplification into the pEF1/His C expression vector
(Invitrogen). For the serine 33 mutant of p53, the mutated fragment
from pGEX-p53 1–86(1–86) A33 was used to replace the corresponding
sequence in wt p53 in pEF1/His C, using a BamHI site
upstream from the ATG initiation codon and an internal SgrI
site in position 241 of the p53 coding sequence. All mutations were
confirmed by sequencing.
Flow Cytometry and Viability Assay.
Attached and nonadherent cells were collected, fixed in 70% ethanol,
washed in PBS, and stained with propidium iodide (25 µg/ml). Samples
were analyzed on a FACScan (Becton Dickinson). Apoptosis was evaluated
as the population of cells in the
sub-G0-G1 peak. Viability
was evaluated by the crystal violet method (22)
.
|
RESULTS |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
-radiation that cause DNA damage by promoting the formation of DNA
double-strand breaks (28)
. As shown in Fig. 1
, exposure of NIH 3T3 cells to two distinct chemotherapeutic drugs, CDDP
and DOX, caused a dramatic increase in the level of active p38, which
was detectable 2 and 1 h after treatment, respectively. In
contrast, lethal doses of -radiation (20 Gy) did not cause a
consistent activation of p38 (<2-fold induction), as has been
described previously (29)
. These observations were further
confirmed by assessing the enzymatic activity of p38 using bacterially
expressed GST-activating transcription factor 2 as a substrate
(data not shown).
|
, both CDDP and DOX provoked
a detectable increase in the level of expression of
p21WAF 3–4 h after treatment, which remained
elevated even after 24 h (data not shown). Similarly,
-radiation induced the expression of p21WAF,
which was detectable as early as 2 h after treatment (Fig. 1A)
. In contrast, the total amount of p38 did not change
with any of the treatments and also served as a loading control.
Thus, these results suggest that p38 is activated in NIH 3T3 cells in
response to chemotherapeutic drugs, such as CDDP and DOX, and that this
activation precedes the enhanced expression of
p21WAF. However, the lack of activation of p38 by
-radiation indicates that this kinase is not a universal sensor for
genotoxic stress.
As an approach to investigate whether p38 affects p53 function, we took
advantage of the availability of two p38-specific inhibitors, SB 253080
and SKF 86002 (30
, 31)
. As shown in Fig. 1B
,
the incubation of the cells in the presence SB 253080 prevented the
increase of p21WAF in response to CDDP, and very
similar results were obtained with SKF 86002 (data not shown). In
contrast, the treatment with SB 253080 did not affect the elevation of
p21WAF expression provoked by -radiation (Fig. 1C)
, suggesting that p38 may participate in signaling to p53
in response to chemotherapeutic DNA-damaging agents, but not when DNA
damage is caused by -radiation. Interestingly, when Western blots
for p53 were performed, we observed that the blockade of p38 did not
cause any demonstrable effect on the accumulation of p53 protein
elicited by these treatments (Fig. 1B
and the text
below), thus indicating that p38 does not affect the protein
levels of p53.
We next set out to investigate whether p38 affects the transcriptional
activity of p53 in response to chemotherapeutic agents, using as a
reporter system the pG13 CAT plasmid, whose expression is controlled by
a tandem of p53-responsive elements (24)
. As shown in Fig. 2A
, exposure of cells to CDDP and DOX resulted in a remarkable
increase in the transcriptional activity of p53 (Fig. 2A)
,
with DOX demonstrating a greater response. When the p38 inhibitor SB
203580 was added, we observed that the transcriptional activation of
p53 by CDDP was nearly abolished, whereas the response to DOX was
largely diminished (Fig. 2B)
. To control for the specificity
of this approach and to exclude the possibility that the p38 inhibitor
affects additional molecules under our assay conditions, we took
advantage of the observation that the replacement of threonine 106 with
methionine renders p38 insensitive to SB 253080
(32)
. We engineered such an epitope-tagged mutant of
p38 and confirmed that SB 253080 prevents the in vitro
activity of p38, but not that of the p38
Met106 mutant
(Fig. 2C)
. Furthermore, as shown in Fig. 2D
,
whereas SB 253080 abolished the p53 response in CDDP-treated NIH 3T3
cells, this response was nearly restored by expression of the
inhibitor-insensitive form of p38 (Fig. 2D)
. Thus, taken
together, these data indicate that p38 participates in the
activation of p53-dependent pathways in response to chemotherapeutic
agents. Furthermore, because SB 253080 did not abolish the response to
DOX, it is also possible that this drug might stimulate additional SB
253080-insensitive isoforms of p38, such as p38 and p38
(32)
, a possibility that is under current investigation.
|
. Thus,
one possible mechanism might involve the control of the nuclear
translocation of p53, a process that is essential for the
transcriptional activity of p53 (33)
. To address this
possibility, we performed immunofluorescence analysis of p53 using
confocal microscopy in cells treated with CDDP or DOX in the presence
or absence of p38 inhibitors. As shown in Fig. 3
, the p38 inhibitors did not affect the accumulation and localization of
the p53 tumor suppressor gene product, thus indicating that p38 or its
downstream targets do not participate in the biochemical route
regulating the translocation of p53 to the nucleus.
|
, p53 coimmunoprecipitates with p38, but not when p38 is
activated by CDDP or UV radiation (control). Thus, inactive p38
can bind to p53, but activation of p38 appears to cause the release of
p53 from the complex. Similar results have been reported for JNK
(16)
. The functional significance of this event is under
investigation. Nonetheless, our previous results using p38 inhibitors
indicated that p38 does not regulate the level and localization of p53,
thus suggesting that an additional mechanism might participate in the
regulation of p53 by p38.
|
, activated p38
phosphorylates both GST-fusion proteins with very high efficiency.
These results prompted us to investigate which residue(s) are
phosphorylated by p38 in the most NH2-terminal 86
amino acids. Serine 15, which has been recently shown to be
phosphorylated by the AT gene (35
, 36)
, was used as a
control. Because p38 is a proline-targeted kinase, we mutated all
serines or threonines adjacent to prolines in this region. Three
residues, serine 33, serine 46, and threonine 81, represent such
potential targets. When using these mutant GST-p53 proteins as
substrates, we observed that the replacement of serine 33 with
alanine abolishes the ability of the
NH2-terminal domain of p53 to serve as an
in vitro substrate for p38 (Fig. 4C)
. All other
mutant proteins behaved as did the wt p53. Thus, the serine 33 residue
in p53 represents a likely candidate as a phosphoacceptor for the
enzymatic activity of p38. On the basis of these results, we generated
a full-length p53 cDNA including a mutation in serine 33 (p53 S33A). wt
p53 and its S33A mutant were then subcloned into a tagging expression
vector (pECF/6His). As shown in Fig. 4D
, both wt p53 and p53
S33A were detectably expressed, as judged by Western blotting with
antibodies against the 6His epitope. Furthermore, an
anti-phospho-serine 33-specific antibody detected the wt 6His-tagged
p53 but not its S33A mutant, thus indicating that serine 33 of p53 can
be phosphorylated in vivo and further supporting the
specificity of this antibody. However, mutation of p53 in serine 33 did
not affect its basal transcriptional activity when expressed in
p53-null cells, such as Saos-2 cells (Fig. 4E)
.
To explore whether serine 33 participates in the transcriptional
activation of p53 by genotoxic chemotherapy, we transfected both wt and
S33A p53 constructs into NIH 3T3 cells. As shown in Fig. 4F
,
expression of wt p53 increased the basal p53-dependent transcriptional
activity in NIH 3T3 cells and caused a remarkable increase in the
reporter activity in response to CDDP. In contrast, the S33A mutant
form of p53 also enhanced the basal activity in these cells but
displayed only a limited response to CDDP when compared with the wt
p53. These results support the importance of serine 33 in the
activation of p53 by genotoxic agents such as CDDP.
To examine whether p38 activation is sufficient to stimulate p53
function, we transfected NIH 3T3 cells with an increasing amount of its
upstream activator, MKK6 (37
, 38)
. A clear dose-response
effect was observed on the activity of p53, thus indicating that the
stimulation of p38 is sufficient to enhance the activity of the
endogenous p53 (Fig. 5A)
. Using a similar approach, we examined the role of serine
33 in the activation of p53 by the MKK6-p38 pathway. To avoid the
background response due to endogenous p53, we chose to use Saos-2 cells
for these experiments. As shown in Fig. 5B
, cotransfection
of p38 and MKK6 induced a remarkable increase in the transcriptional
response to p53. However, activation of the p38 pathway provoked a very
limited activation of the p53 S33A mutant. Similar results were
obtained in NIH 3T3 cells (data not shown). Furthermore, the use of the
p53 phospho-serine 33-specific antibody revealed that the in
vivo phosphorylation of this p53 residue increases on CDDP
treatment and that this response can be inhibited by the use of p38
blockers (Fig. 5C)
. These findings strongly suggest that
p38 can activate p53 directly and that transcriptional activation of
p53 by p38 involves the phosphorylation of p53 in serine 33.
|
, control cells exposed to CDDP displayed an apoptotic
fraction of 20–25%, whereas this fraction was reduced to 10–13% by
treatment with p38 inhibitors. These results were further supported by
a cell viability assay, which helped demonstrate that the treatment
with p38 inhibitors resulted in a 2-fold increase in the
IC50 of CDDP (Fig. 6B)
, a remarkable
increase that can be regarded as significant in terms chemoresistance.
This decrease in the effectiveness of CDDP suggests that p38 is
necessary for the correct execution of the apoptotic program initiated
by p53 after genotoxic stress induced by CDDP.
|
|
DISCUSSION |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
-radiation and UV radiation
has been extensively investigated among these agents. For
example, serines 15, 33, and 37 have been shown to be phosphorylated by
both stimuli (6
, 7)
. However, there are some differences
in the phosphorylation pattern of p53, including the status of
phosphorylation on serine 392, which is only phosphorylated in response
to UV light (40
, 41) . Much less is understood about the
role of p53 phosphorylation in the activation of the p53 pathway on
genotoxic stress when induced by other classes of DNA-damaging agents,
including the many widely used chemotherapeutic drugs.
Interestingly, we found that treatment of cells with CDDP and DOX,
which are frequently used for the treatment of cancer patients, can
cause the sustained activation of p38, a member of MAPK superfamily
of proline-targeted serine/threonine protein kinases. In contrast,
lethal doses of -radiation failed to stimulate p38 activity.
Thus, activation of p38 appears not to result from DNA damage but to
be triggered in response to genotoxic stress provoked specifically by
the formation of DNA adducts and by inhibition of topoisomerase II. The
molecular mechanisms responsible for this selective activation are
still unclear and are being actively investigated. Nonetheless, the
availability of specific p38 inhibitors (30
, 31)
afforded the possibility of exploring its contribution to the cellular
responses to genotoxic stress. Indeed, blockade of p38 revealed that
this kinase is necessary for the activation of p53-dependent
transcription in response to chemotherapeutic agents, as judged by the
remarkable inhibition of the accumulation of
p21WAF and the activation of reporter systems by
the treatment with p38 inhibitors. In contrast, blockade of p38
did not prevent the increase in p21WAF expression
provoked by -radiation, thus further supporting the specificity of
this approach. Together, these results support a role for p38 in the
response to genotoxic stress caused by chemotherapeutic agents, likely
by activating p53 function.
A role in p53 activation has been proposed recently for another
stress-activated kinase family member, JNK (16
, 17)
. In
this case, the inactive form of JNK was found to bind p53 and to
diminish the cellular pool of p53 by targeting its degradation
(16
, 17)
. On activation, JNK appears to dissociate from
p53, thus enhancing the stability of the newly synthesized p53 protein.
However, activation of JNK alone does not appear to be sufficient to
increase p53 activity because no increase was detected in the
transcriptional activity of p53 on expression of molecules such as MAPK
kinase kinase 1 that effectively stimulate JNK-dependent transcription
in our cellular system (20)
. In contrast, activation of
p38 is itself sufficient to increase the activity of the endogenous
p53 in cells expressing wt p53, such as NIH 3T3 cells, and on
expression of wt p53 in a p53-null background, such as that seen in
Saos-2 cells (42)
. p38 was also found to
coimmunoprecipitate with p53; however, in this case, we did not obtain
any evidence that p38 can affect the level of p53 protein or its
intracellular distribution or that blockade of p38 affects the
accumulation of p53 in the nucleus on genotoxic stress. In
contrast, we obtained evidence that p53 could be a relevant substrate
for p38.
Transcriptional activation of the tumor suppressor p53 is often
achieved by phosphorylation of key regulatory residues (6
, 43)
. Indeed, extensive phosphorylation on the
NH2-terminal transactivating domain of p53 has
been reported in response to physical or chemically induced damage to
the DNA, thus providing a mechanism by which p53 can act as a universal
sensor for DNA damage (1)
. For instance, serine 15 is
phosphorylated in response to -radiation by the product of the AT
gene (35
, 36)
and by others members of the AT-related
protein family (44)
, thus stimulating p53.
Similarly, DNA-protein kinase (PK) may be involved in the
transcriptional activation of p53 through phosphorylation in serine 15
(45)
, although this issue still remains unclear (46
, 47)
. Serine 37 may be also targeted for phosphorylation, and
several candidate kinases have been proposed, including ATR or
DNA-PK (44
, 48)
. Serine 33 has also been described
as a target for kinase activity after DNA damage, and although this
residue can be phosphorylated in vitro by JNK and the cyclin
H-CDK7-p36 MAT complex (21
, 49 , 50)
, the identity of the
actual kinase acting on p53 serine 33 in response to DNA damage remains
elusive (8
, 51)
. In this regard, several lines of evidence
suggest that p38 can phosphorylate the transactivating domain of p53 in
serine 33. In vitro, p38 can phosphorylate GST-fusion
protein containing the NH2-terminal,
transactivating domain of p53, and mutational analysis revealed that
among all candidate residues, serine 33 was the phosphoacceptor site.
To confirm the relevance of these in vitro data, we
reconstituted a p53 with a mutation in residue serine 33. Under basal
conditions, we did not detect any significant difference between this
mutant form and the wt p53 in expression level or ability to stimulate
expression from reporter plasmids, as reported previously
(52)
. However, the serine 33 mutant of p53 failed to
respond transcriptionally to CDDP treatment and to its direct
activation of p38 in both wt p53 and p53-null cellular
backgrounds. Taken together, these data strongly suggest that
the serine 33 residue of p53 is a biologically relevant target for the
enzymatic activity of p38.
Another residue, serine 392, has also been described recently as a site
for p38 phosphorylation (53
, 54)
. However, this site is
not adjacent to a proline residue, thus representing an unlikely
candidate for direct phosphorylation by proline-targeted kinases,
including p38. Furthermore, phosphorylation of this site was only
observed after UV irradiation of cells (40
, 41)
, a
condition that might activate a number of additional kinases, including
the double-stranded RNA activated protein kinase (PKR)
(55)
, which has previously been described as a candidate
to phosphorylate this particular residue. Thus, although we cannot
exclude the possibility that p38 may also directly or indirectly
phosphorylate additional residues in p53, including serine 392, the
available evidence suggests that these putative events might not be
sufficient to activate p53 in the absence of serine 33.
In summary, our work demonstrates that the activation of p38 and the
subsequent phosphorylation, at least in residue 33, is a critical event
in the response of p53 to genotoxic stress and provides the first
evidence that p38 might represent the highly sought after DNA
damage-induced p53 serine 33 kinase. Furthermore, the use of specific
p38 inhibitors revealed that interfering with this kinase diminishes
apoptosis and enhances the viability of cells exposed to
chemotherapeutic agents. These findings are in line with the pivotal
role of p53 in the cytotoxic response to drugs such as CDDP or DOX and
further support a key role for p38 in the stimulation of p53 in
response to these DNA-damaging agents. Interestingly, these results
also suggest that p38 should be explored as a putative mechanism to
explain chemoresistance. Further work will be necessary to fully
elucidate the molecular mechanism leading to the activation of p38
by genotoxic stress and to investigate the likely clinical consequences
of these findings in the search for novel approaches to improve cancer
therapy.
|
ACKNOWLEDGMENTS |
|---|
|
FOOTNOTES |
|---|
1 R. S-P. was partially supported by the North
Atlantic Treated Organization Science Program. J. M. R. was
supported by Grants FIS-BAE 98/5093 and FIS 98/1336 from the Instituto
de Salud Carlos III, Spain. 
2 Present address: Unidad de Biología
Celular, Centro Nacional de Biología Fundamental, Instituto de
Salud, Carlos III carretera Majadahonda-Pozuelo, Km 2 Majadahonda,
28220 Madrid, Spain.
3 To whom requests for reprints should be
addressed, at Oral and Pharyngeal Cancer Branch, National Institute of
Dental and Craniofacial Research, NIH, 30 Convent Drive, Building 30,
Room 211, Bethesda, MD 20892-4330. Phone: (301) 496-6259; Fax: (301)
402-0823; E-mail: sg39v{at}nih.gov
4 The abbreviations used are: MAPK,
mitogen-activated protein kinase; JNK, c-Jun-NH2-terminal
kinase; ß-gal, ß-galactosidase; DOX, doxorubicin; CDDP, cisplatin;
CAT, chloramphenicol acetyltransferase; GST, glutathione
S-transferase; HA, hemagglutinin; wt, wild-type; MKK6,
MAPK kinase 6.
Received 11/ 2/99. Accepted 3/ 6/00.
|
REFERENCES |
|---|
|
TopABSTRACTINTRODUCTIONMATERIALS AND METHODSRESULTSDISCUSSIONREFERENCES |
|---|
radiation. Proc. Natl. Acad. Sci. USA, 95: 2834-2837, 1998. radiation or etoposide-induced DNA damage, results in the phosphorylation of the murine p53 protein at serine-389. Proc. Natl. Acad. Sci. USA, 95: 6399-6402, 1998.This article has been cited by other articles:
|
|
 |
|
  J. J. Gamsby, J. J. Loros, and J. C. Dunlap A Phylogenetically Conserved DNA Damage Response Resets the Circadian Clock J Biol Rhythms, June 1, 2009; 24(3): 193 - 202. [Abstract] [PDF]
|
|
|
|
 |
|
 D. Zhu, J. Wu, C. Spee, S. J. Ryan, and D. R. Hinton BMP4 Mediates Oxidative Stress-induced Retinal Pigment Epithelial Cell Senescence and Is Overexpressed in Age-related Macular Degeneration J. Biol. Chem., April 3, 2009; 284(14): 9529 - 9539. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. K. Hoffmann, I. H. Lambert, and S. F. Pedersen Physiology of Cell Volume Regulation in Vertebrates Physiol Rev, January 1, 2009; 89(1): 193 - 277. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Kawahara, T. Hori, K. Chonabayashi, T. Oka, M. Sudol, and T. Uchiyama Kpm/Lats2 is linked to chemosensitivity of leukemic cells through the stabilization of p73 Blood, November 1, 2008; 112(9): 3856 - 3866. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T.-C. Ho, S.-L. Chen, Y.-C. Yang, C.-Y. Chen, F.-P. Feng, J.-W. Hsieh, H.-C. Cheng, and Y.-P. Tsao 15-Deoxy-{Delta}(12,14)-prostaglandin J2 Induces Vascular Endothelial Cell Apoptosis through the Sequential Activation of MAPKS and p53 J. Biol. Chem., October 31, 2008; 283(44): 30273 - 30288. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Yoda, K. Toyoshima, Y. Watanabe, N. Onishi, Y. Hazaka, Y. Tsukuda, J. Tsukada, T. Kondo, Y. Tanaka, and Y. Minami Arsenic Trioxide Augments Chk2/p53-mediated Apoptosis by Inhibiting Oncogenic Wip1 Phosphatase J. Biol. Chem., July 4, 2008; 283(27): 18969 - 18979. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Callejas-Valera, J. Guinea-Viniegra, C. Ramirez-Castillejo, J. A. Recio, E. Galan-Moya, N. Martinez, J. M. Rojas, S. R. y Cajal, and R. Sanchez-Prieto E1a Gene Expression Blocks the ERK1/2 Signaling Pathway by Promoting Nuclear Localization and MKP Up-regulation: IMPLICATION IN v-H-Ras-INDUCED SENESCENCE J. Biol. Chem., May 9, 2008; 283(19): 13450 - 13458. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 Z. Derdak, N. M. Mark, G. Beldi, S. C. Robson, J. R. Wands, and G. Baffy The Mitochondrial Uncoupling Protein-2 Promotes Chemoresistance in Cancer Cells Cancer Res., April 15, 2008; 68(8): 2813 - 2819. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 P.-C. Chang and M. Li Kaposi's Sarcoma-Associated Herpesvirus K-Cyclin Interacts with Cdk9 and Stimulates Cdk9-Mediated Phosphorylation of p53 Tumor Suppressor J. Virol., January 1, 2008; 82(1): 278 - 290. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 I. Manov, Y. Bashenko, A. Eliaz-Wolkowicz, M. Mizrahi, O. Liran, and T. C. Iancu High-Dose Acetaminophen Inhibits the Lethal Effect of Doxorubicin in HepG2 Cells: The Role of P-glycoprotein and Mitogen-Activated Protein Kinase p44/42 Pathway J. Pharmacol. Exp. Ther., September 1, 2007; 322(3): 1013 - 1022. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E Tiligada Chemotherapy: induction of stress responses Endocr. Relat. Cancer, December 1, 2006; 13(Supplement_1): S115 - S124. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
W. H. Faour, Q. He, A. Mancini, D. Jovanovic, J. Antoniou, and J. A. Di Battista Prostaglandin E2 Stimulates p53 Transactivational Activity through Specific Serine 15 Phosphorylation in Human Synovial Fibroblasts: ROLE IN SUPPRESSION OF c/EBP/NF-{kappa}B-MEDIATED MEKK1-INDUCED MMP-1 EXPRESSION J. Biol. Chem., July 21, 2006; 281(29): 19849 - 19860. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Yoshida, H. Liu, and Y. Miki Protein Kinase C {delta} Regulates Ser46 Phosphorylation of p53 Tumor Suppressor in the Apoptotic Response to DNA Damage J. Biol. Chem., March 3, 2006; 281(9): 5734 - 5740. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 J. V. Thottassery, L. Westbrook, H. Someya, and W. B. Parker c-Abl-independent p73 stabilization during gemcitabine- or 4'-thio-{beta}-D-arabinofuranosylcytosine-induced apoptosis in wild-type and p53-null colorectal cancer cells. Mol. Cancer Ther., February 1, 2006; 5(2): 400 - 410. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. I. Walton, S. C. Wilson, I. R. Hardcastle, A. R. Mirza, and P. Workman An evaluation of the ability of pifithrin-{alpha} and -{beta} to inhibit p53 function in two wild-type p53 human tumor cell lines Mol. Cancer Ther., September 1, 2005; 4(9): 1369 - 1377. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. B. Friis, C. R. Friborg, L. Schneider, M.-B. Nielsen, I. H. Lambert, S. T. Christensen, and E. K. Hoffmann Cell shrinkage as a signal to apoptosis in NIH 3T3 fibroblasts J. Physiol., September 1, 2005; 567(2): 427 - 443. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. G. Viniegra, N. Martinez, P. Modirassari, J. H. Losa, C. P. Cobo, V. J. S.-A. Lobo, C. I. A. Luquero, L. Alvarez-Vallina, S. Ramon y Cajal, J. M. Rojas, et al. Full Activation of PKB/Akt in Response to Insulin or Ionizing Radiation Is Mediated through ATM J. Biol. Chem., February 11, 2005; 280(6): 4029 - 4036. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. Gadea, L. Roger, C. Anguille, M. de Toledo, V. Gire, and P. Roux TNF{alpha} induces sequential activation of Cdc42- and p38/p53-dependent pathways that antagonistically regulate filopodia formation J. Cell Sci., December 15, 2004; 117(26): 6355 - 6364. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 O. M. Fischer, S. Hart, A. Gschwind, N. Prenzel, and A. Ullrich Oxidative and Osmotic Stress Signaling in Tumor Cells Is Mediated by ADAM Proteases and Heparin-Binding Epidermal Growth Factor Mol. Cell. Biol., June 15, 2004; 24(12): 5172 - 5183. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
M. Watabe, K. Hishikawa, A. Takayanagi, N. Shimizu, and T. Nakaki Caffeic Acid Phenethyl Ester Induces Apoptosis by Inhibition of NF{kappa}B and Activation of Fas in Human Breast Cancer MCF-7 Cells J. Biol. Chem., February 13, 2004; 279(7): 6017 - 6026. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 A. Porras, S. Zuluaga, E. Black, A. Valladares, A. M. Alvarez, C. Ambrosino, M. Benito, and A. R. Nebreda p38{alpha} Mitogen-activated Protein Kinase Sensitizes Cells to Apoptosis Induced by Different Stimuli Mol. Biol. Cell, February 1, 2004; 15(2): 922 - 933. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
K. Naka, A. Tachibana, K. Ikeda, and N. Motoyama Stress-induced Premature Senescence in hTERT-expressing Ataxia Telangiectasia Fibroblasts J. Biol. Chem., January 16, 2004; 279(3): 2030 - 2037. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 S. Manes, E. Mira, R. Colomer, S. Montero, L. M. Real, C. Gomez-Mouton, S. Jimenez-Baranda, A. Garzon, R. A. Lacalle, K. Harshman, et al. CCR5 Expression Influences the Progression of Human Breast Cancer in a p53-dependent Manner J. Exp. Med., November 3, 2003; 198(9): 1381 - 1389. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
L. Yuan, W.-M. Yu, and C.-K. Qu DNA Damage-induced G2/M Checkpoint in SV40 Large T Antigen-immortalized Embryonic Fibroblast Cells Requires SHP-2 Tyrosine Phosphatase J. Biol. Chem., October 31, 2003; 278(44): 42812 - 42820. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. Brancho, N. Tanaka, A. Jaeschke, J.-J. Ventura, N. Kelkar, Y. Tanaka, M. Kyuuma, T. Takeshita, R. A. Flavell, and R. J. Davis Mechanism of p38 MAP kinase activation in vivo Genes & Dev., August 15, 2003; 17(16): 1969 - 1978. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
I. A. Vasilevskaya, T. V. Rakitina, and P. J. O'Dwyer Geldanamycin and its 17-Allylamino-17-Demethoxy Analogue Antagonize the Action of Cisplatin in Human Colon Adenocarcinoma Cells: Differential Caspase Activation as a Basis for Interaction Cancer Res., June 15, 2003; 63(12): 3241 - 3246. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S. Chen, N. Nguyen, K. Tamura, M. Karin, and R. H. Tukey The Role of the Ah Receptor and p38 in Benzo[a]pyrene-7,8-dihydrodiol and Benzo[a]pyrene-7,8-dihydrodiol-9,10-epoxide-induced Apoptosis J. Biol. Chem., May 23, 2003; 278(21): 19526 - 19533. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
C. Henderson, M. Mizzau, G. Paroni, R. Maestro, C. Schneider, and C. Brancolini Role of Caspases, Bid, and p53 in the Apoptotic Response Triggered by Histone Deacetylase Inhibitors Trichostatin-A (TSA) and Suberoylanilide Hydroxamic Acid (SAHA) J. Biol. Chem., March 28, 2003; 278(14): 12579 - 12589. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
A. Ryo, Y.-C. Liou, K. P. Lu, and G. Wulf Prolyl isomerase Pin1: a catalyst for oncogenesis and a potential therapeutic target in cancer J. Cell Sci., March 1, 2003; 116(5): 773 - 783. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
G. M. Wulf, Y.-C. Liou, A. Ryo, S. W. Lee, and K. P. Lu Role of Pin1 in the Regulation of p53 Stability and p21 Transactivation, and Cell Cycle Checkpoints in Response to DNA Damage J. Biol. Chem., December 6, 2002; 277(50): 47976 - 47979. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.-J. Kim, S.-G. Hwang, D. Y. Shin, S.-S. Kang, and J.-S. Chun p38 Kinase Regulates Nitric Oxide-induced Apoptosis of Articular Chondrocytes by Accumulating p53 via NFkappa B-dependent Transcription and Stabilization by Serine 15 Phosphorylation J. Biol. Chem., August 30, 2002; 277(36): 33501 - 33508. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. M. Grana, E. V. Rusyn, H. Zhou, C. I. Sartor, and A. D. Cox Ras Mediates Radioresistance through Both Phosphatidylinositol 3-Kinase-dependent and Raf-dependent but Mitogen-activated Protein Kinase/Extracellular Signal-regulated Kinase Kinase-independent Signaling Pathways Cancer Res., July 15, 2002; 62(14): 4142 - 4150. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 D. M. Smith, A. Kazi, L. Smith, T. E. Long, B. Heldreth, E. Turos, and Q. P. Dou A Novel beta -Lactam Antibiotic Activates Tumor Cell Apoptotic Program by Inducing DNA Damage Mol. Pharmacol., June 1, 2002; 61(6): 1348 - 1358. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
H. Kishi, K. Nakagawa, M. Matsumoto, M. Suga, M. Ando, Y. Taya, and M. Yamaizumi Osmotic Shock Induces G1 Arrest through p53 Phosphorylation at Ser33 by Activated p38MAPK without Phosphorylation at Ser15 and Ser20 J. Biol. Chem., October 12, 2001; 276(42): 39115 - 39122. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 E. J. Lee, W. R. Duan, M. Jakacka, B. D. Gehm, and J. L. Jameson Dominant Negative ER Induces Apoptosis in GH4 Pituitary Lactotrope Cells and Inhibits Tumor Growth in Nude Mice Endocrinology, September 1, 2001; 142(9): 3756 - 3763. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
R. G. Deschesnes, J. Huot, K. Valerie, and J. Landry Involvement of p38 in Apoptosis-associated Membrane Blebbing and Nuclear Condensation Mol. Biol. Cell, June 1, 2001; 12(6): 1569 - 1582. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
T. Buschmann, O. Potapova, A. Bar-Shira, V. N. Ivanov, S. Y. Fuchs, S. Henderson, V. A. Fried, T. Minamoto, D. Alarcon-Vargas, M. R. Pincus, et al. Jun NH2-Terminal Kinase Phosphorylation of p53 on Thr-81 Is Important for p53 Stabilization and Transcriptional Activities in Response to Stress Mol. Cell. Biol., April 15, 2001; 21(8): 2743 - 2754. [Abstract] [Full Text]
|
|
|
|
|
|
V. M. Gonzalez, M. A. Fuertes, C. Alonso, and J. M. Perez Is Cisplatin-Induced Cell Death Always Produced by Apoptosis? Mol. Pharmacol., April 1, 2001; 59(4): 657 - 663. [Full Text]
|
|
|
|
|
|
M. Parra, M. Jardi, M. Koziczak, Y. Nagamine, and P. Munoz-Canoves p53 Phosphorylation at Serine 15 Is Required for Transcriptional Induction of the Plasminogen Activator Inhibitor-1 (PAI-1) Gene by the Alkylating Agent N-Methyl-N'-nitro-N-nitrosoguanidine J. Biol. Chem., September 21, 2001; 276(39): 36303 - 36310. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
S.-J. Kim, J.-W. Ju, C.-D. Oh, Y.-M. Yoon, W. K. Song, J.-H. Kim, Y. J. Yoo, O.-S. Bang, S.-S. Kang, and J.-S. Chun ERK-1/2 and p38 Kinase Oppositely Regulate Nitric Oxide-induced Apoptosis of Chondrocytes in Association with p53, Caspase-3, and Differentiation Status J. Biol. Chem., January 4, 2002; 277(2): 1332 - 1339. [Abstract] [Full Text] [PDF]
|
|
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH | TABLE OF CONTENTS |
| Cancer Research | Clinical Cancer Research |
| Cancer Epidemiology Biomarkers & Prevention | Molecular Cancer Therapeutics |
| Molecular Cancer Research | Cancer Prevention Research |
| Cancer Prevention Journals Portal | Cancer Reviews Online |
| Annual Meeting Education Book | Meeting Abstracts Online |
