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A novel WEE1 pathway for replication stress responses
Ting Pan1, Qi Qin1, Chubing Nong1
1College of Life Science and Technology, Huazhong Agricultural University, Wuhan, Hubei, China.
Abstract:
DNA replication stress poses a severe threat to genome stability and is a hallmark of cancer as well as a target for cancer therapy. It is well known that the evolutionarily conserved protein kinase WEE1 regulates replication stress responses by directly phosphorylating and inhibiting the major cell cycle driver CDKs in many organisms. Here, we report a novel WEE1 pathway. We found that Arabidopsis WEE1 directly interacts with and phosphorylates the E3 ubiquitin ligase FBL17 that promotes the degradation of CDK inhibitors. The phosphorylated FBL17 is further polyubiquitinated and degraded, thereby leading to the accumulation of CDK inhibitors and the inhibition of CDKs. In strong support for this model, either loss of function of FBL17 or overexpression of CDK inhibitors suppresses the hypersensitivity of the wee1 mutant to replication stress. Intriguingly, human WEE1 also phosphorylates and destabilizes the FBL17 equivalent protein SKP2, indicating that this is a conserved mechanism. This study reveals that the WEE1-FBL17/SKP2-CKIs-CDKs axis is a molecular framework for replication stress responses, which may have clinical implications because the WEE1 inhibitor AZD1775 is currently in phase II clinical trial as an anticancer drug.
Insights
Scientists discovered a new WEE1 protein pathway that helps cells respond to DNA replication stress. This pathway involves FBL17/SKP2, leading to CDK inhibitor accumulation and CDK inhibition, crucial for genome stability and cancer therapy.
Area of Science:
- Molecular Biology
- Plant Science
- Cancer Research
Background:
- DNA replication stress threatens genome stability and is a cancer hallmark.
- WEE1 kinase is known to regulate replication stress by inhibiting CDKs.
Purpose of the Study:
- To elucidate a novel WEE1-mediated pathway in response to replication stress.
- To investigate the role of FBL17 in WEE1 signaling.
Main Methods:
- Investigated protein-protein interactions between WEE1 and FBL17 in Arabidopsis.
- Analyzed phosphorylation and ubiquitination of FBL17.
- Assessed the impact of FBL17 loss-of-function and CDK inhibitor overexpression on wee1 mutant phenotypes.
- Examined the homologous interaction in human cells.
Main Results:
- Arabidopsis WEE1 directly interacts with and phosphorylates E3 ligase FBL17.
- Phosphorylated FBL17 undergoes polyubiquitination and degradation, increasing CDK inhibitors.
- Loss of FBL17 or increased CDK inhibitors rescues wee1 mutant replication stress sensitivity.
- Human WEE1 phosphorylates and destabilizes SKP2, a FBL17 homolog.
Conclusions:
- Identified the conserved WEE1-FBL17/SKP2-CKIs-CDKs axis as a key replication stress response pathway.
- This pathway regulates CDK activity through targeted degradation of inhibitors.
- The findings have potential clinical implications for WEE1 inhibitor-based cancer therapy.
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