Identification of the oncogenic kinase TOPK/PBK as a master mitotic regulator of C2H2 zinc finger proteins
Raed Rizkallah1, Paratchata Batsomboon2, Gregory B Dudley2
1Department of Biomedical Sciences, Florida State University, Tallahassee, Florida, 32306, United States of America.
Abstract:
TOPK/PBK is an oncogenic kinase upregulated in most human cancers and its high expression correlates with poor prognosis. TOPK is known to be activated by Cdk1 and needed for mitotic cell division; however, its mitotic functions are not yet fully understood. In this study, we show that TOPK plays a global mitotic role by simultaneously regulating hundreds of DNA binding proteins. C2H2 zinc finger proteins (ZFPs) constitute the largest family of human proteins. All C2H2 ZFPs contain a highly conserved linker sequence joining their multi-zinc finger domains. We have previously shown that phosphorylation of this conserved motif serves as a global mechanism for the coordinate dissociation of C2H2 ZFPs from condensing chromatin, during mitosis. Here, using a panel of kinase inhibitors, we identified K252a as a potent inhibitor of mitotic ZFP linker phosphorylation. We generated a biotinylated form of K252a and used it to purify candidate kinases. From these candidates we identified TOPK/PBK, in vitro and in vivo, as the master ZFP linker kinase. Furthermore, we show precise temporal correlation between TOPK activating phosphorylation by Cdk1 and linker phosphorylation in mitosis. The identification of this fundamental role of TOPK underscores its significance as a promising novel target of cancer therapeutics.
Insights
The study identifies TOPK (T-loop phosphorylation kinase) as the master kinase regulating hundreds of DNA binding proteins during cell division. This discovery highlights TOPK as a crucial new target for cancer therapeutics.
Area of Science:
- Molecular Biology
- Cell Biology
- Oncology
Background:
- The oncogenic kinase TOPK (T-loop phosphorylation kinase)/PBK is upregulated in many cancers, correlating with poor prognosis.
- TOPK is activated by Cdk1 and essential for mitotic cell division, but its precise functions remain unclear.
Purpose of the Study:
- To elucidate the global mitotic role of TOPK in regulating DNA binding proteins.
- To identify the specific kinase responsible for phosphorylating the conserved linker motif in C2H2 zinc finger proteins (ZFPs) during mitosis.
Main Methods:
- Utilized a panel of kinase inhibitors to identify K252a as an inhibitor of mitotic ZFP linker phosphorylation.
- Generated a biotinylated K252a to purify candidate kinases, identifying TOPK/PBK.
- Investigated the temporal correlation between Cdk1-mediated TOPK activation and ZFP linker phosphorylation.
Main Results:
- TOPK/PBK was identified as the master kinase for ZFP linker phosphorylation, both in vitro and in vivo.
- TOPK regulates hundreds of DNA binding proteins, including C2H2 ZFPs, by phosphorylating their conserved linker sequences.
- Mitotic ZFP linker phosphorylation is temporally correlated with TOPK activation by Cdk1.
Conclusions:
- TOPK plays a fundamental, global role in mitosis by coordinating the dissociation of numerous DNA binding proteins from chromatin.
- The identification of TOPK as the master ZFP linker kinase establishes it as a significant and promising therapeutic target for cancer treatment.
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