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Published on: November 29, 2014
Determination of the Plk4/Sak consensus phosphorylation motif using peptide spots arrays
Genie C Leung1, Cynthia S W Ho, Ivan M Blasutig
1Centre for Systems Biology, Samuel Lunenfeld Research Institute, Mount Sinai Hospital, Room 1090 A, Toronto, Ont, Canada.
Abstract:
The family of polo like kinases (Plks) regulate cell cycle progression through key functional roles in mitosis. While the four mammalian family members, Plk1-4, share overlapping functions, each member possesses unique functions that may be dictated in part by their ability to phosphorylate different substrates. Numerous cellular substrates for Plk1, 2, and 3 have been characterized, but the protein targets for Plk4/Sak remain unknown. We have purified the kinase domain of Sak and demonstrated that it has robust kinase activity in vitro. Using in vitro kinase assays on peptide spots arrays, we determined the consensus phosphorylation motif for Sak to be yen-[Ile/Leu/Val]-Ser/Thr-phi-phi-X- yen/Pro (where phi denotes a large hydrophobic residue, yen is a charged residue dependent on the context of the surrounding sequence, and residues in brackets are unfavoured). This consensus phosphorylation motif differs from that of Plk1, and provides a basis for future studies to identify in vivo substrates of Sak.
Insights
Polo-like kinases (Plks) regulate cell division. Researchers identified the specific phosphorylation motif for Plk4/Sak, a key step toward discovering its unknown protein targets and understanding its unique mitotic roles.
Area of Science:
- Cell Biology
- Molecular Biology
- Biochemistry
Background:
- Polo-like kinases (Plks) are crucial regulators of cell cycle progression and mitosis.
- While Plk1-3 substrates are known, the in vivo targets of Plk4/Sak remain unidentified.
- Plk family members exhibit unique functions potentially linked to substrate specificity.
Purpose of the Study:
- To characterize the substrate specificity of Plk4/Sak.
- To determine the consensus phosphorylation motif for Plk4/Sak.
- To provide a foundation for identifying Plk4/Sak's in vivo substrates.
Main Methods:
- Purification of the kinase domain of Sak.
- In vitro kinase assays utilizing peptide spot arrays.
- Determination of the consensus phosphorylation motif through biochemical analysis.
Main Results:
- The purified Sak kinase domain exhibited robust in vitro kinase activity.
- The consensus phosphorylation motif for Sak was determined as yen-[Ile/Leu/Val]-Ser/Thr-phi-phi-X- yen/Pro.
- This motif differs significantly from that of Plk1.
Conclusions:
- The identified phosphorylation motif provides a critical tool for future research.
- This discovery paves the way for identifying novel in vivo substrates of Plk4/Sak.
- Understanding Plk4/Sak substrates will elucidate its unique roles in mitosis and cell cycle regulation.
