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Transcription factor ATF2 regulation by the JNK signal transduction pathway
S Gupta1, D Campbell, B Dérijard
1Department of Biochemistry and Molecular Biology, University of Massachusetts Medical School, Worcester 01605.
Abstract:
Treatment of cells with pro-inflammatory cytokines or ultraviolet radiation causes activation of the c-Jun NH2-terminal protein kinase (JNK). Activating transcription factor-2 (ATF2) was found to be a target of the JNK signal transduction pathway. ATF2 was phosphorylated by JNK on two closely spaced threonine residues within the NH2-terminal activation domain. The replacement of these phosphorylation sites with alanine inhibited the transcriptional activity of ATF2. These mutations also inhibited ATF2-stimulated gene expression mediated by the retinoblastoma (Rb) tumor suppressor and the adenovirus early region 1A (E1A) oncoprotein. Furthermore, expression of dominant-negative JNK inhibited ATF2 transcriptional activity. Together, these data demonstrate a role for the JNK signal transduction pathway in transcriptional responses mediated by ATF2.
Insights
Pro-inflammatory cytokines and UV radiation activate c-Jun NH2-terminal protein kinase (JNK). JNK targets Activating Transcription Factor-2 (ATF2), regulating its transcriptional activity and downstream gene expression.
Area of Science:
- Cellular signaling pathways
- Molecular biology
- Gene regulation
Background:
- Pro-inflammatory cytokines and ultraviolet radiation are cellular stressors.
- c-Jun NH2-terminal protein kinase (JNK) is a key signaling kinase.
- Activating Transcription Factor-2 (ATF2) is a transcription factor involved in cellular responses.
Purpose of the Study:
- To investigate the role of the JNK signaling pathway in regulating ATF2 transcriptional activity.
- To identify the specific interaction between JNK and ATF2.
- To elucidate the impact of JNK-mediated ATF2 phosphorylation on gene expression.
Main Methods:
- Cell treatment with pro-inflammatory cytokines and UV radiation.
- Analysis of ATF2 phosphorylation by JNK.
- Site-directed mutagenesis of ATF2 phosphorylation sites.
- Assays for ATF2 transcriptional activity and gene expression.
- Expression of dominant-negative JNK.
Main Results:
- JNK phosphorylates ATF2 on two threonine residues in its activation domain.
- Mutating these phosphorylation sites abolished ATF2 transcriptional activity.
- Mutations in ATF2 phosphorylation sites inhibited ATF2-stimulated gene expression mediated by Rb and E1A.
- Dominant-negative JNK expression inhibited ATF2 transcriptional activity.
Conclusions:
- The JNK signaling pathway plays a critical role in regulating ATF2-mediated transcriptional responses.
- JNK-dependent phosphorylation of ATF2 is essential for its transcriptional activity.
- This pathway is involved in gene expression regulation influenced by tumor suppressors and oncoproteins.