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A PIM-CHK1 signaling pathway regulates PLK1 phosphorylation and function during mitosis
Kévin Adam1,2, Maëlle Cartel2,3, Mireille Lambert1,2
1Institut Cochin, INSERM U1016, CNRS UMR 8104, Université Paris Descartes, 75014 Paris, France.
Abstract:
Although the kinase CHK1 is a key player in the DNA damage response (DDR), several studies have recently provided evidence of DDR-independent roles of CHK1, in particular following phosphorylation of its S280 residue. Here, we demonstrate that CHK1 S280 phosphorylation is cell cycle-dependent and peaks during mitosis. We found that this phosphorylation was catalyzed by the kinase PIM2, whose protein expression was also increased during mitosis. Importantly, we identified polo-like kinase 1 (PLK1) as a direct target of CHK1 during mitosis. Genetic or pharmacological inhibition of CHK1 reduced the activating phosphorylation of PLK1 on T210, and recombinant CHK1 was able to phosphorylate T210 of PLK1 in vitro Accordingly, S280-phosphorylated CHK1 and PLK1 exhibited similar specific mitotic localizations, and PLK1 was co-immunoprecipitated with S280-phosphorylated CHK1 from mitotic cell extracts. Moreover, CHK1-mediated phosphorylation of PLK1 was dependent on S280 phosphorylation by PIM2. Inhibition of PIM proteins reduced cell proliferation and mitotic entry, which was rescued by expressing a T210D phosphomimetic mutant of PLK1. Altogether, these data identify a new PIM-CHK1-PLK1 phosphorylation cascade that regulates different mitotic steps independently of the CHK1 DDR function.This article has an associated First Person interview with the first author of the paper.
Insights
Checkpoint kinase 1 (CHK1) regulates mitosis through a novel PIM-CHK1-PLK1 pathway. This cascade controls cell proliferation and mitotic entry independently of DNA damage response functions.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Checkpoint kinase 1 (CHK1) is crucial for DNA damage response (DDR).
- Emerging evidence suggests DDR-independent roles for CHK1, particularly involving S280 phosphorylation.
- Mitotic regulation is complex and involves intricate phosphorylation events.
Purpose of the Study:
- To elucidate the DDR-independent functions of CHK1 during mitosis.
- To identify the upstream kinases and downstream targets of CHK1 S280 phosphorylation.
- To characterize a novel signaling pathway regulating mitotic progression.
Main Methods:
- Cell cycle analysis and western blotting to assess CHK1 S280 phosphorylation.
- Kinase assays using recombinant proteins to determine enzymatic activity.
- Genetic and pharmacological inhibition studies in cell lines.
- Immunoprecipitation and immunofluorescence to study protein localization and interactions.
Main Results:
- CHK1 S280 phosphorylation is cell cycle-dependent, peaking in mitosis, and catalyzed by PIM2 kinase.
- Polo-like kinase 1 (PLK1) is a direct downstream target of CHK1 during mitosis, with CHK1 phosphorylating PLK1 at T210.
- The PIM-CHK1-PLK1 cascade regulates cell proliferation and mitotic entry, independent of CHK1's DDR role.
Conclusions:
- A novel PIM-CHK1-PLK1 phosphorylation cascade regulates mitotic progression.
- This pathway operates independently of CHK1's canonical DNA damage response functions.
- Targeting this cascade offers potential therapeutic strategies for cell proliferation disorders.
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