Related Experiment Video
Updated: Feb 5, 2026
Experimental Approaches to Study Mitochondrial Localization and Function of a Nuclear Cell Cycle Kinase, Cdk1
Published on: February 25, 2016
Premature activation of Cdk1 leads to mitotic events in S phase and embryonic lethality
Radoslaw Szmyd1,2, Joanna Niska-Blakie1,3, M Kasim Diril1,4
1Institute of Molecular and Cell Biology (IMCB), A*STAR (Agency for Science, Technology and Research), 61 Biopolis Drive, Proteos #3-09, Singapore, 138673, Republic of Singapore.
Abstract:
Cell cycle regulation, especially faithful DNA replication and mitosis, are crucial to maintain genome stability. Cyclin-dependent kinase (CDK)/cyclin complexes drive most processes in cellular proliferation. In response to DNA damage, cell cycle surveillance mechanisms enable normal cells to arrest and undergo repair processes. Perturbations in genomic stability can lead to tumor development and suggest that cell cycle regulators could be effective targets in anticancer therapy. However, many clinical trials ended in failure due to off-target effects of the inhibitors used. Here, we investigate in vivo the importance of WEE1- and MYT1-dependent inhibitory phosphorylation of mammalian CDK1. We generated Cdk1AF knockin mice, in which two inhibitory phosphorylation sites are replaced by the non-phosphorylatable amino acids T14A/Y15F. We uncovered that monoallelic expression of CDK1AF is early embryonic lethal in mice and induces S phase arrest accompanied by γH2AX and DNA damage checkpoint activation in mouse embryonic fibroblasts (MEFs). The chromosomal fragmentation in Cdk1AF MEFs does not rely on CDK2 and is partly caused by premature activation of MUS81-SLX4 structure-specific endonuclease complexes, as well as untimely onset of chromosome condensation followed by nuclear lamina disassembly. We provide evidence that tumor development in liver expressing CDK1AF is inhibited. Interestingly, the regulatory mechanisms that impede cell proliferation in CDK1AF expressing cells differ partially from the actions of the WEE1 inhibitor, MK-1775, with p53 expression determining the sensitivity of cells to the drug response. Thus, our work highlights the importance of improved therapeutic strategies for patients with various cancer types and may explain why some patients respond better to WEE1 inhibitors.
Insights
Altering CDK1 phosphorylation sites causes embryonic lethality and DNA damage in mice, impacting cancer therapy development. This research reveals new insights into cell cycle regulation and potential therapeutic strategies for cancer treatment.
Area of Science:
- Cell Biology
- Molecular Biology
- Genetics
Background:
- Cell cycle regulation is vital for genome stability, with cyclin-dependent kinases (CDKs) driving proliferation.
- DNA damage triggers cell cycle arrest for repair, but disruptions can lead to cancer.
- Targeting cell cycle regulators offers anticancer therapy potential, yet clinical trials face challenges due to off-target effects.
Purpose of the Study:
- To investigate the in vivo role of WEE1- and MYT1-dependent inhibitory phosphorylation of mammalian CDK1.
- To generate and analyze Cdk1AF knockin mice with non-phosphorylatable CDK1 sites (T14A/Y15F).
Main Methods:
- Generation of Cdk1AF knockin mice.
- Analysis of mouse embryonic fibroblasts (MEFs) for cell cycle arrest, DNA damage markers (γH2AX), and checkpoint activation.
- Assessment of chromosomal fragmentation and its causes, including MUS81-SLX4 endonuclease and chromosome condensation.
- Evaluation of tumor development in the liver of CDK1AF expressing mice.
- Comparison of CDK1AF effects with the WEE1 inhibitor MK-1775, considering p53 expression.
Main Results:
- Monoallelic expression of CDK1AF is early embryonic lethal in mice.
- CDK1AF MEFs exhibit S phase arrest, γH2AX, DNA damage checkpoint activation, and chromosomal fragmentation.
- Chromosomal fragmentation is independent of CDK2 and partly due to premature MUS81-SLX4 activation and untimely chromosome condensation.
- Tumor development in the liver of CDK1AF expressing mice is inhibited.
- CDK1AF effects on proliferation differ from MK-1775, with p53 influencing cellular response.
Conclusions:
- Inhibitory phosphorylation of CDK1 is essential for embryonic development and preventing DNA damage.
- CDK1AF induces distinct cellular responses compared to WEE1 inhibition, highlighting the complexity of cell cycle regulation.
- Understanding these mechanisms can inform improved therapeutic strategies for various cancers and explain differential patient responses to WEE1 inhibitors.
Related Concept Videos
01:22Phase-lead and Phase-lag Controllers
01:24Time and frequency -Domain Interpretation of Phase-lead Control
The design of phase-lead control involves the strategic placement of poles and zeros to balance steady-state error and system...
02:27The Mitotic Spindle
The bipolar configuration of the mitotic spindle facilitates chromosomal segregation, preparing the cell for division. One mechanism that ensures...
02:41Lethal Alleles
Lucien Cuénot discovered lethal alleles in 1905 while studying the inheritance of coat color in mice. The agouti gene is responsible for the color of the coat in mice. This gene codes for an agouti-signaling protein, which is responsible for melanin distribution in mammals. The wild-type allele gives rise to gray-brown coat color in mice, while the mutant allele gives rise to yellow coat color. In addition to coat color, the agouti gene is associated with the yellow...
02:53Conservative Site-specific Recombination and Phase Variation
The recognition sites for Cre recombinase called LoxP...
02:39Phase Diagrams