The Activation of c-Jun NH2-terminal Kinase (JNK) by DNA-damaging Agents Serves to Promote Drug Resistance via Activating Transcription Factor 2 (ATF2)-dependent Enhanced DNA Repair

Abstract

The activating transcription factor 2 (ATF2) is a member of the ATF/cAMP-response element-binding protein family of basic-leucine zipper proteins involved in cellular stress response. The transcription potential of ATF2 is enhanced markedly by NH 2 -terminal phosphorylation by c-Jun NH 2 -terminal kinase (JNK) and mediates stress responses including DNA-damaging events. We have observed that four DNA-damaging agents (cisplatin, actinomycin D, MMS, and etoposide), but not the cisplatin isomer, transplatin, which does not readily damage DNA, strongly activate JNK, p38, and extracellular signal-regulated kinase (ERK), and strongly increase phosphorylation and ATF2-dependent transcriptional activity. Selective inhibition studies with PD98059, SB202190, SP600125, and the dominant negative JNK indicate that activation of JNK but not p38 kinase or ERK kinase is required for the phosphorylation and transcriptional activation of ATF2. Stable expression of ATF2 in human breast carcinoma BT474 cells increases transcriptional activity and confers resistance to the four DNA-damaging agents, but not to transplatin. Conversely, stable expression of a dominant negative ATF2 (dnATF2) quantitatively blocks phosphorylation of endogenous ATF2 leading to a marked decrease in transcriptional activity by endogenous ATF2 and a markedly increased sensitivity to the four agents as judged by decreased cell viability. Similarly, application of SB202190 at 50 M or SP600125 inhibited JNK activity, blocked transactivation, and sensitized parental cells to the four DNA-damaging drugs. Moreover, the wild type ATF2-expressing clones exhibited rapid DNA repair after treatment with the four DNA-damaging agents but not transplatin. Conversely, expression of dnATF2 quantitatively blocks DNA repair. These results indicate that JNK-dependent phosphorylation of ATF2 plays an important role in the drug resistance phenotype likely by mediating enhanced DNA repair by a p53-independent mechanism. JNK may be a rational target for sensitizing tumor cells to DNA-damaging chemotherapy agents.

Translocation of human ribosomal protein S3 to sites of DNA damage is dependant on ERK-mediated phosphorylation following genotoxic stress

“…ERK is known to respond to both oxidative stress and alkylating agents [38]. Notably, our data would suggest that ERK is perhaps more sensitive to oxidative stress than alkylating agents since HEK 293 cells exposed to hydrogen peroxide accumulated roughly twice as much nuclear S3 as did exposure to the two alkylating agents when cell survival was at 70%.…”

ATF2 contributes to cisplatin resistance in non‐small cell lung cancer and celastrol induces cisplatin resensitization through inhibition of JNK/ATF2 pathway

“…This data are in agreement with a previous study reporting a correlation between ATF2 expression and the resistance to CDDP treatment in breast carcinoma BT474 cell line. 8 In details, Shah et al identified the same nuclear punctiform pattern shown in Figure 2 and concluded that such peculiar staining could indicate ATF2 localization in DNA repair foci following DNA damage. 35 Our results indicate that Celastrol, an active triterpene extracted by the Chinese herb "Thunder of God Vine", downmodulates ATF2-mediated transcription in a dose dependent manner (Fig.…”

“…ATF2 is a member of the helix-loop-helix b-ZIP transcription factor family, often associated to chemo-and radioresistance. 8,33 Agents that inhibit ATF2 activate, both in vitro and in vivo, apoptotic pathways leading to an increased response to radio-and chemo-therapy. 34 In the present study, we reported a correlation between ATF2 protein expression, as total and phosphorylated form, and CDDP resistance ( Fig.…”

“…[8]1DrugB. [8]). Briefly, MTS was added according to manufacturer's instructions (Promega) and after 1-2 hr of incubation at 37 C, the absorbance at 490 nm was recorded by ELISA reader.…”

“…Hayakawa et al showed that stable expression of ATF2 in human breast carcinoma cells BT474 conferring resistance to DNA-damaging agents, secondary to an increased DNA repair ability and this status may be reverted by blocking ATF2 activation using JNK inhibitor (SP600125). 8 Furthermore, cJUN/ATF2 complex play a role in cell transformation by inducing anchorage and/ or growth factor-independent proliferation. 9 Similar findings were also reported in melanoma and, in this type of tumor, ATF2 nuclear localization is associated with poor prognosis.…”