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Regulation of c-Myc through phosphorylation at Ser-62 and Ser-71 by c-Jun N-terminal kinase
K Noguchi1, C Kitanaka, H Yamana
1Biophysics Division, National Cancer Center Research Institute, 5-1-1 Tsukiji, Chuo-ku, Tokyo 104-0045, Japan.
Abstract:
The expression of c-myc promotes cell proliferation and also sensitizes cells to various extracellular apoptotic stimuli. However, signal pathways regulating the function of Myc proteins during apoptosis are unknown. c-Jun N-terminal kinase (JNK) is activated by various apoptotic stimuli, but neither the target molecule(s) or the action of JNK has been identified in Myc-mediated apoptosis. Here, we found that JNK selectively interacted with, and phosphorylated, c-Myc at Ser-62 and Ser-71 as confirmed with phospho-c-Myc-specific antibodies. Interestingly, dominant negative mutant JNK(APF) impaired the c-Myc-dependent apoptosis, but not mutated c-Myc (S62A/S71A)-dependent apoptosis triggered by UV irradiation. Furthermore, c-Myc (S62A/S71A)-expressing NIH3T3 cells were not sensitized like wild type c-Myc-expressing NIH3T3 cells to JNK-activating apoptotic stimuli, such as UV and Taxol. These results indicate that the JNK pathway is selectively involved in the c-Myc-mediated apoptosis and that the apoptotic function of c-Myc is directly regulated by JNK pathway through phosphorylation at Ser-62 and Ser-71.
Insights
The c-Jun N-terminal kinase (JNK) pathway phosphorylates c-Myc, a key protein in cell proliferation, directly regulating its apoptotic function. This phosphorylation is crucial for Myc-mediated apoptosis.
Area of Science:
- Cell Biology
- Molecular Biology
- Oncology
Background:
- c-Myc protein promotes cell proliferation and sensitizes cells to apoptosis.
- Signaling pathways regulating Myc protein function during apoptosis remain largely unknown.
- c-Jun N-terminal kinase (JNK) is activated by apoptotic stimuli, but its role in Myc-mediated apoptosis is unclear.
Purpose of the Study:
- To investigate the signaling pathways regulating Myc protein function during apoptosis.
- To identify the role of c-Jun N-terminal kinase (JNK) in Myc-mediated apoptosis.
- To elucidate the molecular mechanism by which JNK influences c-Myc's apoptotic activity.
Main Methods:
- Utilized phospho-c-Myc-specific antibodies to confirm JNK interaction and phosphorylation of c-Myc at Ser-62 and Ser-71.
- Employed dominant-negative JNK (JNK(APF)) mutants to assess the impact on c-Myc-dependent apoptosis.
- Generated and analyzed NIH3T3 cells expressing wild-type or mutated c-Myc (S62A/S71A) to evaluate sensitization to apoptotic stimuli.
Main Results:
- Demonstrated that JNK selectively interacts with and phosphorylates c-Myc at specific serine residues (Ser-62 and Ser-71).
- Showed that dominant-negative JNK impaired c-Myc-dependent apoptosis, while mutated c-Myc (S62A/S71A) abrogated this effect.
- Found that cells expressing mutated c-Myc were not sensitized to JNK-activating apoptotic stimuli (UV, Taxol) compared to wild-type c-Myc cells.
Conclusions:
- The JNK pathway is selectively involved in c-Myc-mediated apoptosis.
- JNK directly regulates the apoptotic function of c-Myc through phosphorylation at Ser-62 and Ser-71.
- Phosphorylation of c-Myc by JNK is a critical step in sensitizing cells to apoptotic stimuli.