Carcinogenesis Advance Access originally published online on July 8, 2006
Carcinogenesis 2007 28(1):183-190; doi:10.1093/carcin/bgl119
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A role for UV-light-induced c-Fos: stimulation of nucleotide excision repair and protection against sustained JNK activation and apoptosis
Department of Toxicology, University of Mainz Germany
*To whom correspondence should be addressed at: Department of Toxicology, University of Mainz, Obere Zahlbacher Strasse 67, D-55131 Mainz, Germany. Tel: ++49 6131 393 3246; Fax: ++49 6131 393 3421; Email: kaina{at}uni-mainz.de
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Abstract |
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UV light (UV-C) is a potent inducer of the c-fos gene. Cells lacking c-Fos are hypersensitive to the cytotoxic effect of UV-C indicating a protective role of c-fos induction. Here we show that cells deficient in c-Fos (fos–/–) are unable to remove cyclobutane pyrimidine dimers (CPDs) from DNA and undergo apoptosis at high frequency via the Fas pathway. We also show that in c-Fos-deficient cells the activation of c-Jun N-terminal kinase (JNK) by UV-C differs from the wild-type (wt, fos+/+). In wt cells JNK activation is transient, returning to control level 5–8 h after treatment, whereas in c-Fos-deficient cells JNK activation was long-lasting and did not return to control level. Inhibition of early JNK activation by the JNK inhibitor SP600125 attenuated CPD repair and increased UV-C induced apoptosis whereas inhibition of late JNK activation attenuated the apoptotic response of c-Fos-deficient cells. Late and sustained activation of JNK resulted in upregulation of fas (CD95, apo-1) ligand and induction of caspase 8-dependent apoptosis. The data indicate that the immediate-early induction of the JNK/c-fos pathway stimulates the repair of UV-C induced DNA lesions that protects against apoptosis. If this does not occur, cells do not recover from transcription blockage leading, as shown for c-Fos-deficient cells, to a reduced expression of MKP1, sustained JNK activation and fasL overexpression that finally results in activation of the death receptor pathway. The data support the hypothesis that non-repaired DNA damage is the cause for the late and sustained activation of the MAP kinase pathway in response to genotoxins.
Abbreviations: CPD, cyclobutane pyrimidine dimers; GGR, global genome repair; JNK, c-Jun N-terminal kinase; MEFs, mouse embryonic fibroblasts; MKP1, MAP kinase phosphatase-1; NER, nucleotide excision repair; p38K, p38 kinase; TCR, transcription coupled repair; wt, wild-type
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Introduction |
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c-Fos is part of the heterodimeric transcription factor AP-1 that is a key regulator for many processes such as cell growth, differentiation, inflammation and malignant transformation. Cells lacking c-Fos are hypersensitive to ultraviolet (UV) light (1) and many other genotoxins (2) suggesting c-Fos to play a role in the cellular protection against DNA-damaging agents. Increased sensitivity of c-Fos-deficient cells to UV light was demonstrated both for primary (3) as well as immortalized (4) mouse embryonic fibroblasts (MEFs) with the end points cytotoxicity and clastogenicity, both were enhanced in comparison to the corresponding isogenic wild-type (wt). Hypersensitivity of c-Fos lacking cells was explained by their impaired recovery from the genotoxin-induced block to DNA replication (2), which could be due to a defect in the repair of critical replication blocking lesions. Indeed, similar to p53-deficient MEFs which are known to display various DNA repair defects (5,6), c-fos knockout cells (fos–/–) display less efficient repair of UV-C lesions (this paper and Christmann et al., in preparation). Therefore, the elucidation of DNA damage triggered signalling and execution of cell death is of importance for a better understanding of why c-Fos knockout cells are hypersensitive to genotoxins.
Stimulation of the transcriptional activity of the fasL gene upon DNA damage appears to play an important role in genotoxin-induced cell death. Thus it has been shown that long-term activation of fasL triggers apoptosis not only after UV-C light treatment, but also upon exposure to the anticancer drug, cisplatin (7,8). Therefore the possibility exists that, upon non-repaired DNA damage, sustained upregulation of fasL is a key component in the induction of apoptosis. Upon cisplatin treatment, upregulation of fasL was preceded by a sustained activation of c-Jun N-terminal kinase (JNK) and p38 kinase (p38K) (7,8). Regulation of the fasL by the SAPK/JNK signalling cascade is well established (9,10). It has been shown that several transcription factors are involved, such as c-Myc, NF-AT, NF-kB and AP-1. Most important in the upregulation of the fasL promoter are NF-kB and AP-1, as shown for etoposide and UV irradiation (11). Whereas the importance of the heterodimeric AP-1 complex consisting of c-Jun and activating transcription factor 2 (ATF2) is well established (9), the role of c-Fos during induction of the fasL gene is not clear.
Here we addressed the role of c-Fos in triggering DNA repair and apoptosis upon UV-C. We used a pair of isogenic MEFs that are wt and knockout for c-fos (fos–/–) and, at the same time, proficient for p53 to investigate specifically the impact of c-Fos on the repair of DNA lesions and apoptosis. We analysed the signalling leading to UV-C induced apoptosis in c-Fos-deficient MEFs, focussing on the role of FasL upregulation and sustained JNK activation in response to non-repaired DNA lesions.
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Material and methods |
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Cell lines
Spontaneously immortalized MEFs were used. The wt (fos+/+-1-98M designated as wt) cell line was a littermate to the c-Fos-deficient cell line used (fos–/–-7-98M designated as fos–/–). Both cell lines were generated from wt or c-fos knockout mouse embryos (C57BL/6, the Jackson Laboratory) as previously described (3). Cells were grown in Dulbecco's minimal essential medium (DMEM) with high glucose and glutamine (Invitrogen) containing 10% inactivated fetal bovine serum (FBS; Gibco Life Technologies) at 37°C in an atmosphere containing 7% CO2.
UV-C light treatment
Growth medium was removed and cells were irradiated with UV-C at a dose rate of 1 J/m2/s with a radium NSE 11-270 low pressure UV-C lamp (Philips). Thereafter the removed (conditioned) medium was re-used and cells were incubated at 37° C for the appropriate time periods.
Determination of apoptosis
To monitor drug-induced apoptosis, cells were stained with propidium iodide (PI) and the sub-G1 fraction was determined by flow cytometry as described previously (12).
Caspase activity assay
The caspase colorimetric assay (R&D Systems) was performed according to the manufacturer's protocol. Briefly, cells were UV-C irradiated or not and after particular intervals of post-exposure, they were trypsinized, counted and collected by centrifugation. Cell pellets were lysed on ice, centrifuged, and the supernatant was transferred and kept on ice. The enzymatic reactions were carried out in 96-well microplates (405 nm, 37°C, 1–2 h) with the addition of equal volume of 2x reaction buffer and appropriate caspase colorimetric substrate prior to the measurement using an enzyme-linked immunosorbent assay.
Preparation of cell extracts and western blot analysis
Whole-cell extracts were prepared as described previously (13). Samples of 25 µg protein were separated by 10% SDS–PAGE and electro-blotted onto nitrocellulose membranes, which were then incubated with antibodies as described previously (14). Primary antibodies were diluted 1:500 in 5% non-fat dry milk, 0.1% Tween–PBS (phosphate-buffered saline) and incubated overnight at 4°C. A polyclonal anti-ERK2 antibody (Santa Cruz Biotechnology) was diluted 1:3000 and incubated 2 h at room temperature. For western blot analysis with phospho-specific antibodies, cells were directly lysed in 1x SDS–PAGE sample buffer and subsequently sonified, as proposed by the manufacturer (Cell Signaling Technology). Phospho-specific antibodies were diluted in 5% bovine serum albumin (BSA), Tris-buffered saline (TBS), and washed with 0.1% Tween–TBS. The protein-antibody complexes were detected by electrochemiluminescence (ECL; Amersham).
South-western slot-blot analysis
Genomic DNA was isolated from sub-confluent growing cells with the use of the QIA(amp) blood mini kit (Qiagen). 0.5 µg DNA were transferred to a positively charged nylon membrane (Hybond plus, Amersham) by vacuum slot-blotting, denaturated with 0.3 M NaOH, neutralized with 5x SSC and fixed by baking the membrane for 2 h at 80°C. Monoclonal antibodies specific for thymine dimers (Kamiya Biomedical Company) were used at a dilution of 1:100. The western blot procedure was performed as described above.
Preparation of RNA and RT–PCR
Total RNA was isolated using the RNA II Isolation Kit from Machery and Nagel. 2 µg RNA were transcribed into cDNA by Superscript II (Invitrogen) in a volume of 40 µl and an aliquot of 3 µl was subjected to RT–PCR. RT-PCR was performed by the use of specific primers (MWG Biotechnology) and Red-Taq Ready Mix (Sigma-Aldrich). The PCR program used was: 1.5 min 94°C, [(denaturing: 45 s, 94°C; annealing: 1 min 56–62°C; elongation: 1 min, 72°C) 25 cycles], 10 min 72°C. Real time RT–PCR were performed using the LightCycler from Roche Diagnostics.
Measurement of RNA synthesis
Transcription blockage upon UV-C exposure was checked by incorporation of [3H]uridine. Cells were exposed to UV-C and cultivated for 1–8 h. 1 h prior to the end of the post-incubation time 0.5 µCi/ml [5,6-3H]uridine (Amersham) was added to the medium. Thereafter cells were washed two times with PBS and 6% TCA (trichloroacetic acid) to remove unincorporated [3H]uridine. Lysis was performed by adding 2 ml 0.1 N NaOH to the cells and overnight incubation. 0.5 ml of the lysate was mixed with 4 ml scintillation cocktail and counted in a liquid scintillation counter. The incorporated radioactivity of the non-UV-C exposed probe was set to 100%.
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Results |
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Levels of p53 and c-Fos and cyclobutane pyrimidine dimer (CPD) removal after UV-C irradiation
To verify the c-Fos status of wt and c-fos knockout cells (fos–/–) used in this study, cells were exposed to UV-C light (20 J/m2) and nuclear extracts were subjected to western blot analysis. As shown in Figure 1A, wt cells display nuclear accumulation of the c-Fos protein 4–8 h after irradiation, whereas, as expected, no signal was detected in fos–/– cells. Since the p53 status can influence the response of cells to UV-C light (6), we carefully checked the expression of p53 upon UV-C exposure in our cell lines used throughout this study. For comparison, we included p53-deficient MEFs (4). As shown in Figure 1B, the cell lines did not express a detectable basal level of nuclear p53. However, the wt and fos–/– cells clearly accumulated p53 in response to UV-C light. This occurred to similar level in both lines (for quantification of time course experiments see Figure 1B, right panel). The data confirmed the p53 wt status of the cells. In line with this, the p53 target genes p21 and gadd45 were upregulated in response to UV-C light in wt and fos–/– cells, indicating p53 to be transcriptionally active in both cell lines (data not shown).
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Next we studied the ability of fos–/– cells to remove CPDs. As shown in Figure 1C (left panel for a representative blot; right panel for quantification of three independent experiments), only wt but not fos–/– cells are able to repair CPDs in the genomic DNA. Thus, in the wt
60% of UV-C induced CPDs were removed within an 18 h post-exposure period after irradiation with 20 J/m2 UV-C, whereas only very weak CPD removal was observed in fos–/– cells.
Apoptosis and caspase activity
To compare the cell lines as to their apoptotic response after UV-C irradiation, apoptosis was measured as a function of time by flow cytometry. Apoptosis occurred earlier and at significant higher frequency in fos–/– cells compared with the wt (Figure 2A). To identify caspases involved in UV-C induced apoptosis, we measured the activation of caspases 3, 8 and 9 under the same treatment conditions (20 J/m2 UV-C). In both cell lines, caspase 3 was activated, with fos–/– cells showing the highest activity (induction factor 3.5) compared with wt cells (2-fold increase). The same was true for caspase 9 (Figure 2B). Increase in caspase 8 activity was observed already 12 h after UV-C exposure only in fos–/– cells; it did not occur in wt cells (Figure 2B).
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Sustained activation of JNK phosphorylation and FasL expression
It was reported that after cisplatin treatment apoptosis induced by DNA damage is signalled by sustained activation of JNK and p38 kinase (p38K) (7,8). To analyse the role of JNK upon UV-C irradiation in wt and fos–/– cells, we analysed its activation by means of phosphorylation specific antibodies and western blot analysis. Exposure with UV-C light caused phosphorylation of JNK already 15 min after irradiation (data not shown). Activation reaches its maximum 2 h after irradiation in both cell lines at a similar level (Figure 3A). In wt cells, it declines thereafter and was not detectable anymore 12 h after UV-C exposure. In contrast, JNK activation in fos–/– cells was still occurring 12 and 18 h after irradiation (Figure 3A). The same was true for activation of the p38K, although the effect was less pronounced than for JNK activation (Figure 3B). To analyse the Fas ligand (fasL) and the Fas receptor (fasR) on transcriptional level after UV-C irradiation, we performed RT–PCR experiments using fasR and fasL specific primers. As shown in Figure 3C, fasL mRNA was only weakly and transiently induced 8 h after exposure in wt cells. c-Fos-deficient cells responded with a sustained upregulation of the fasL mRNA at all time points, i.e. 8–24 h after UV-C exposure. This indicates that c-Fos is not essential for the AP-1 mediated induction of the FasL; it rather prevents it. RT–PCR experiments with fasR specific primers revealed a transient induction of fasR mRNA in both cell lines, 12 and 18 h after irradiation (Figure 3C). To quantify the induction of the fasL mRNA, we performed real time RT–PCR. The data showed an up to 20-fold induction of the fasL mRNA in fos–/– cells but none in the wt 18 h after treatment, (Figure 3D).
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Effect of JNK inhibition on DNA repair
As shown in Figure 3, wt and fos–/– cells responded to UV-C with activation of JNK within 2 h after exposure. This immediate-early activation is supposed to act protectively by activation of DNA repair. To assess the importance of early JNK activation for DNA repair, we made use of the JNK inhibitor SP600125 (15). Wt cells were either pre-treated or not pre-treated for 1 h with 10 µM SP600215. Protein extract was isolated and JNK phosphorylation was measured by means of specific antibodies and western blot analysis. As shown in Figure 4A, non-pretreated wt cells exhibited p-JNK 2–6 h after UV-C exposure whereas in SP600125 pre-treated cells JNK phosphorylation was clearly abolished. Thus, SP600125 prevents the activation of JNK by blocking JNK phosphorylation. Next we studied the effect of JNK inhibition on nucleotide excision repair (NER). Interestingly, SP600125 pre-treatment clearly abrogated the removal of CPDs as observed 6-18 h after UV-C treatment in wt cells (Figure 4B, left panel for a representative blot, right panel for quantification). The data supports the hypothesis that the early induction of JNK upon UV-C exerts a protective effect on cells by stimulation of NER.
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Effect of JNK/p38K inhibition on cellular sensitivity
To study the role of early and late (sustained) JNK activation on cellular sensitivity in more detail, we applied SP600125 1 h before or 9 h after UV-C treatment in order to block either early or late JNK activation, and elucidated the effect of this blockage on apoptosis. As shown in Figure 5A, after pre-treatment of fos–/– cells with SP600125 for 1 h, no phosphorylation of JNK was observed 3 or 6 h after exposure to 20 J/m2 UV-C. Also, when cells were post-treated with SP600125, which was administered 9 h after UV-C irradiation, a strong reduction in the amount of phosphorylated JNK was observed 12 or, to slightly less extent, 18 h after UV-C. Pre-treatment with SP600125 for 1 h attenuated early JNK activation and increased the sensitivity of wt but not c-Fos-deficient cells to UV-C (Figure 5B). In contrast, treatment with SP600125 late (9 h) after UV-C irradiation completely abolished late JNK activation and simultaneously protected c-Fos-deficient cells from UV-C induced apoptosis (Figure 5C). Is this protection related to a change in fasL expression that impacts apoptosis? Indeed, inhibition of late JNK activation provoked a clear reduction of fasL induction, as shown by real-time RT–PCR (Figure 5D, left panel) and semi-quantative PCR (Figure 5D, right panel).
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Expression of MKP1
Sustained activation of JNK was reported to be due to impaired dephosphorylation of JNK by MAP kinase phosphatase-1 (MKP1) (16). Therefore, we determined the expression of MKP1 upon UV-C exposure in wt and c-Fos-deficient cells. As shown in Figure 6, a reduction of MKP1 expression was observed in fos–/– but not wt cells 12 and 18 h after UV-C treatment on RNA level (Figure 6A), and 18 and 24 h after UV-C on protein level (Figure 6B). A reason for the diminished expression of MKP1 could be increased transcription blockage, as it was reported for human fibroblasts derived from Cockayne's syndrome patients (16). As shown in Figure 6C, in both cell lines transcriptional activity was reduced 2–6 h after UV-C irradiation (20 J/m2) by 70% (measured by 3H-uridine incorporation). This transcription blockage was abrogated in wt cells 12–24 h after UV-C, which coincides with the removal of CPDs (Figure 1B). Most interestingly, in fos–/– cells no recovery from the block to transcription was observed. Therefore, we propose the hypothesis that downmodulation of MKP1 at transcriptional level in cells deficient in c-Fos is due to the lack of repair of CPDs.
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Discussion |
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MEFs deficient in c-Fos are hypersensitive to UV-C light (1,3,4) suggesting that c-Fos plays a role in cellular protection against DNA-damaging agents. It would be reasonable to suppose that regulation of DNA repair genes is involved in c-Fos mediated protection. Indeed, as shown here, c-Fos-deficient cells show a defect in the removal of UV-C induced lesions from DNA. It is important to note that the cell lines used in our study are phenotypically p53 wt, which was confirmed by the induction of p53 target genes p21 and gadd45 in both cell lines (data not shown). Therefore, the molecular mechanism underlying the repair defect in fos–/– cells is different from the one already reported to cause the repair defect in p53-deficient MEFs (6). Non-removed CPDs in c-Fos-deficient cells result in a pronounced activation of caspases-3 and -9 whereas caspase-8 was only activated in fos–/– cells. In both cell lines, the mitochondrial pathway was activated by UV-C as indicated by the induction of noxa mRNA (data not shown). NOXA interacts and inhibits anti-apoptotic proteins such as Bcl-2 and BclXL (17). Other changes in the expression of proteins involved in mitochondrial apoptosis were not found (data not shown). Since in MEFs deficient for c-Fos caspase-8 was activated, we speculated that the Fas (CD95/Apo-1) system gets additionally activated in c-Fos-deficient cells, being responsible for their hypersensitivity.
Two mechanisms are involved in activating the Fas system. The first is upregulation of the Fas receptor, the second is based on upregulation of the Fas ligand. In wt and c-Fos-deficient cells we observed a clear increase in the mRNA level of fasR following UV-C treatment. However, only in c-Fos-deficient cells sustained (8–24 h) upregulation of fasL mRNA was observed, which is in contrast to wt cells in which fasL was activated only transiently (up to 8 h after UV-C exposure). Sustained upregulation of the fasL gene might lead to an accumulation of FasL to a given threshold level at which signalling finally is effective resulting in caspase-8 activation. This obviously occurs in c-Fos-deficient but not wt cells upon moderate doses of UV-C.
Induction of transcription of the fasL gene is a key component of the apoptotic pathway, which is mediated via the SAPK/JNK signalling cascade (9,10) that ends up with the activation of AP-1. While its components c-Jun, ATF2 and FosB were reported to participate in the induction of FasL (9,18,19), the role of c-Fos remains unclear. Since fasL induction does occur in fos–/– cells, it indicates that c-Fos is not essential for FasL upregulation; it rather prevents from it.
In c-Fos-deficient cells the induction of the fasL was preceded by a sustained and long-lasting activation of JNK (Fig. 3A) and AP-1 (data not shown). This is in contrast to wt cells in which only an early and transient activation of JNK was observed. We should note that sustained activation of JNK upon UV-C was also observed in normal cells not impaired in c-Fos (20). In this case, however, the dose applied was extremely high (up to 300 J/m2). The early activation of AP-1, described in numerous papers as the so-called immediate-early UV response (21), was proposed to protect against genotoxins since cells lacking c-Fos display a genotoxin hypersensitive phenotype that pertains to cell death and chromosomal aberration formation (1,2). The hypersensitive phenotype of c-Fos-deficient cells remained enigmatic. Here we show that increased sensitivity of c-Fos-deficient cells to UV light is due to impaired repair of CPD lesions. Using the JNK inhibitor SP600125, which binds to the ATP-binding domain of JNK and thus inhibits phosphorylation of JNK target proteins including JNK itself (15), we show that early JNK activation is required for the removal of CPDs. Thus, early JNK activation that triggers upregulation of c-Fos appears to play a key role in the regulation of NER.
Several genes involved in NER are under control of c-Jun/ATF2 such as ercc1 and xpa (22). Whether these genes are regulated by c-Fos in mouse cells and whether a differential expression of these genes in fos–/– cells is related to the observed phenotype is currently under investigation. Rodent cells display a very low level of global genome repair (GGR) (23–25) which is due to decreased expression of DDB2, the main recognition factor for CPDs (26). Therefore, the defect in CPD removal observed in fos–/– cells may reflect a defect in transcription coupled repair (TCR) rather than GGR. This supposition is supported by the strong depression of RNA synthesis upon UV-C in c-Fos-deficient cells. Whether JNK activation is also involved in the regulation of other repair pathways in response to DNA damage remains to be seen. We should note that several DNA repair genes such as MGMT (27), msh2 (28) and the apurinic endonuclease 1 (29) are regulated by AP-1.
To study the impact of the early and late (sustained) JNK activation on the sensitivity of cells, we used SP600125 to block either the early or the late JNK activation. These experiments revealed different biological consequences of JNK, depending on the time of activation after UV-C exposure. Inhibition of early JNK activation enhanced UV-C induced apoptosis in wt cells, suggesting that early JNK activation regulates anti-apoptotic functions upon UV-C radiation such as DNA repair. In this process c-Fos seems to be limiting, since the sensitivity of cells cannot be further increased if JNK inhibition occurs in c-Fos-deficient cells. When the treatment of c-Fos-deficient cells with SP600125 occurred 9 h after UV-C irradiation, a strong reduction in the amount of phosphorylated JNK was observed in the period 12–18 h after exposure. At the same time fasL induction was attenuated and the hypersensitivity of c-Fos-deficient cells to UV-C was abrogated. In wt cells that did not display late and sustained JNK activation, post-treatment with SP600125 had no effect on the cell's sensitivity. This supports that sustained JNK activation in c-Fos-deficient cells upregulates the level of FasL that finally activates the receptor driven apoptotic pathway.
How can sustained JNK activation be achieved? There are at least two possibilities. First, It can be achieved by attenuated dephosphorylation of JNK by MKP1. This mechanism has recently been described for human TCR-deficient fibroblasts as a result of Pol II inhibition (16). Second, it may be due to augmentation of de-novo phosphorylation based on active signalling (30). We observed downregulation of MKP1 concomitant with transcriptional blockage, indicating attenuated dephosphorylation plays a role. Increased de novo phosphorylation may, however, also be involved since sustained phosphorylation of JNK was significantly reduced by SP600125 applied 9 h after UV-C exposure. Therefore, sustained JNK activation is likely to be a mixed effect due to MKP1 inhibition and increased de novo phosphorylation in response to non-repaired DNA lesions. Overall, the data are in line with a model where the early activation of JNK exerts protection by stimulation of NER, whereas the late and sustained activation of JNK counteract survival signals and activates the apoptotic pathway. From the biological point of view, this scenario is beneficial for maintaining genomic integrity: NER is stimulated in response to DNA damage and, if repair does not occur in time, cells will be eliminated before DNA lesions will be fixed as mutations.
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Acknowledgments |
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Work was supported by Deutsche Forschungsgemeinschaft, Ka 724 12-1 and 13-1, and the Mildred Scheel Stiftung for Cancer Research. Funding to pay for the open access publication charges for this article was provided by University of Mainz.
Conflict of Interest Statement: None declared.
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References |
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TopAbstractIntroductionMaterial and methodsResultsDiscussionReferences |
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- Haas S. and Kaina B. (1995) c-Fos is involved in the cellular defence against the genotoxic effect of UV radiation. Carcinogenesis 16:985–991.
[Abstract/Free Full Text] - Kaina B., Haas S., Kappes H. (1997) A general role for c-Fos in cellular protection against DNA-damaging carcinogens and cytostatic drugs. Cancer Res. 57:2721–2731.
[Abstract/Free Full Text] - Lackinger D. and Kaina B. (2000) Primary mouse fibroblasts deficient for c-Fos, p53 or for both proteins are hypersensitive to UV light and alkylating agent-induced chromosomal breakage and apoptosis. Mutat Res. 457:113–123.[Web of Science][Medline]
- Lackinger D., Eichhorn U., Kaina B. (2001) Effect of ultraviolet light, methyl methanesulfonate and ionizing radiation on the genotoxic response and apoptosis of mouse fibroblasts lacking c-Fos, p53 or both. Mutagenesis. 16:233–241.
[Abstract/Free Full Text] - Ford J.M. and Hanawalt P.C. (1997) Expression of wt p53 is required for efficient global genomic nucleotide excision repair in UV-irradiated human fibroblasts. J. Biol. Chem. 272:28073–28080.
[Abstract/Free Full Text] - Smith M.L., Ford J.M., Hollander M.C., Bortnick R.A., Amundson S.A., Seo Y.R., Deng C.X., Hanawalt P.C., Fornace A.J. Jr. (2000) p53-mediated DNA repair responses to UV radiation: studies of mouse cells lacking p53, p21, and/or gadd45 genes. Mol. Cell. Biol. 20:3705–3714.
[Abstract/Free Full Text] - Brozovic A., Fritz G., Christmann M., Zisowsky J., Jaehde U., Osmak M., Kaina B. (2004) Long-term activation of SAPK/JNK, p38 kinase and fas-L expression by cisplatin is attenuated in human carcinoma cells that acquired drug resistance. Int. J. Cancer 112:974–985.[CrossRef][Web of Science][Medline]
- Mansouri A., Ridgway L.D., Korapati A.L., Zhang Q., Tian L., Wang Y., Siddik Z.H., Mills G.B., Claret F.X. (2003) Sustained activation of JNK/p38 MAPK pathways in response to cisplatin leads to Fas ligand induction and cell death in ovarian carcinoma cells. J. Biol. Chem. 278:19245–19256.
[Abstract/Free Full Text] - Faris M., Latinis K.M., Kempiak S.J., Koretzky G.A., Nel A. (1998) Stress-induced Fas ligand expression in T cells is mediated through a MEK kinase 1-regulated response element in the Fas ligand promoter. Mol. Cell. Biol. 18:5414–5424.
[Abstract/Free Full Text] - Faris M., Kokot N., Latinis K., Kasibhatla S., Green D.R., Koretzky G.A., Nel A. (1998) The c-Jun N-terminal kinase cascade plays a role in stress-induced apoptosis in Jurkat cells by up-regulating Fas ligand expression. J. Immunol. 160:134–144.
[Abstract/Free Full Text] - Kasibhatla S., Brunner T., Genestier L., Echeverri F., Mahboubi A., Green D.R. (1998) DNA-damaging agents induce expression of Fas ligand and subsequent apoptosis in T lymphocytes via the activation of NF-kappa B and AP-1. Mol. Cell 1:543–551.[CrossRef][Web of Science][Medline]
- Nicoletti I., Migliorati G., Pagliacci M.C., Grignani F., Riccardi C. (1991) A rapid and simple method for measuring thymocyte apoptosis by propidium iodide staining and flow cytometry. J. Immunol. Methods 139:271–279.[CrossRef][Web of Science][Medline]
- Christmann M. and Kaina B. (2000) Nuclear translocation of mismatch repair proteins MSH2 and MSH6 as a response of cells to alkylating agents. J. Biol. Chem. 275:36256–36262.
[Abstract/Free Full Text] - Christmann M., Tomicic M.T., Kaina B. (2002) Phosphorylation of mismatch repair proteins MSH2 and MSH6 affecting MutS{alpha} mismatch-binding activity. Nucleic Acids. Res. 30:1959–1966.
[Abstract/Free Full Text] - Bennett B.L., Sasaki D.T., Murray B.W., et al. (2001) SP600125, an anthrapyrazolone inhibitor of Jun N-terminal kinase. Proc. Natl Acad. Sci. USA 98:13681–13686.
[Abstract/Free Full Text] - Hamdi M., Kool J., Cornelissen-Steijger P., et al. (2005) DNA damage in transcribed genes induces apoptosis via the JNK pathway and the JNK-phosphatase MKP-1. Oncogene 24:7135–7144.[CrossRef][Web of Science][Medline]
- Oda E., Ohki R., Murasawa H., Nemoto J., Shibue T., Yamashita T., Tokino T., Taniguchi T., Tanaka N. (2000) Noxa, a BH3-only member of the Bcl-2 family and candidate mediator of p53-induced apoptosis. Science 288:1053–1058.
[Abstract/Free Full Text] - Baumann S., Hess J., Eichhorst S.T., Krueger A., Angel P., Krammer P.H., Kirchhoff S. (2003) An unexpected role for FosB in activation-induced cell death of T cells. Oncogene 22:1333–1339.[CrossRef][Web of Science][Medline]
- Kolbus A., Herr I., Schreiber M., Debatin K.M., Wagner E.F., Angel P. (2000) c-Jun-dependent CD95-L expression is a rate-limiting step in the induction of apoptosis by alkylating agents. Mol. Cell. Biol. 20:575–582.
[Abstract/Free Full Text] - Chen Y.R., Wang X., Templeton D., Davis R.J., Tan T.H. (1996) The role of c-Jun N-terminal kinase (JNK) in apoptosis induced by ultraviolet C and gamma radiation. Duration of JNK activation may determine cell death and proliferation. J. Biol. Chem. 271:31929–31936.
[Abstract/Free Full Text] - Angel P. and Karin M. (1991) The role of Jun, Fos and the AP-1 complex in cell-proliferation and transformation. Biochim. Biophys. Acta 1072:129–157.[Medline]
- Hayakawa J., Mittal S., Wang Y., Korkmaz K.S., Adamson E., English C., Ohmichi M., McClelland M., Mercola D. (2004) Identification of promoters bound by c-Jun/ATF2 during rapid large-scale gene activation following genotoxic stress. Mol. Cell 16:521–535.[CrossRef][Web of Science][Medline]
- Bohr V.A., Smith C.A., Okumoto D.S., Hanawalt P.C. (1985) DNA repair in an active gene: removal of pyrimidine dimers from the DHFR gene of CHO cells is much more efficient than in the genome overall. Cell 40:359–369.[CrossRef][Web of Science][Medline]
- Vreeswijk M.P., van Hoffen A., Westland B.E., Vrieling H., van Zeeland A.A., Mullenders L.H. (1994) Analysis of repair of cyclobutane pyrimidine dimers and pyrimidine 6-4 pyrimidone photoproducts in transcriptionally active and inactive genes in Chinese hamster cells. J. Biol. Chem. 269:31858–31863.
[Abstract/Free Full Text] - Ruven H.J., Berg R.J., Seelen C.M., Dekkers J.A., Lohman P.H., Mullenders L.H., van Zeeland A.A. (1993) Ultraviolet-induced cyclobutane pyrimidine dimers are selectively removed from transcriptionally active genes in the epidermis of the hairless mouse. Cancer Res. 53:1642–1645.
[Abstract/Free Full Text] - Tan T. and Chu G. (2002) p53 binds and activates the xeroderma pigmentosum DDB2 gene in humans but not mice. Mol. Cell. Biol. 22:3247–3254.
[Abstract/Free Full Text] - Boldogh I., Ramana C.V., Chen Z., Biswas T., Hazra T.K., Grosch S., Grombacher T., Mitra S., Kaina B. (1998) Regulation of expression of the DNA repair gene O6-methylguanine-DNA methyltransferase via protein kinase C-mediated signaling. Cancer Res. 58:3950–3956.
[Abstract/Free Full Text] - Scherer S.J., Maier S.M., Seifert M., Hanselmann R.G., Zang K.D., Muller-Hermelink H.K., Angel P., Welter C., Schartl M. (2000) p53 and c-Jun functionally synergize in the regulation of the DNA repair gene hMSH2 in response to UV. J. Biol. Chem. 275:37469–37473.
[Abstract/Free Full Text] - Grosch S. and Kaina B. (1999) Transcriptional activation of apurinic/apyrimidinic endonuclease (Ape, Ref-1) by oxidative stress requires CREB. Biochem. Biophys. Res. Commun. 261:859–863.[CrossRef][Web of Science][Medline]
- Fritz G. and Kaina B. (2006) Late activation of stress kinases (SAPK/JNK) by genotoxins requires the DNA repair proteins DNA-PKcs and CSB. Mol. Biol. Cell 17:851–861.
[Abstract/Free Full Text]
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