Polo-like kinase 4 autodestructs by generating its Slimb-binding phosphodegron.

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Polo-like kinase 4 (Plk4) is crucial for centriole assembly.
• Interphase Plk4 protein levels are actively regulated to prevent centriole overduplication.
• SCF(Slimb/βTrCP) complex mediates Plk4 degradation during interphase.

Purpose of the Study:

• Investigate the role of Plk4 autophosphorylation in regulating its stability.
• Determine how Plk4 generates its Slimb-binding phosphodegron.
• Analyze the impact of mutations within the Slimb-recognition motif (SRM) on Plk4 levels and centriole duplication.

Main Methods:

• Mass spectrometry of in-vitro-phosphorylated Plk4 and purified Plk4.
• Site-directed mutagenesis of phosphorylatable residues within the Plk4 SRM.
• Expression of Plk4 mutants in Drosophila S2 cells to assess protein levels and centriole duplication.

Main Results:

• Plk4 directly autophosphorylates to generate its own Slimb-binding phosphodegron.
• Autophosphorylation of Ser293 within the SRM is critical for Slimb binding and ubiquitination.
• Multiple residues flanking Ser293 collectively enhance SCF(Slimb) binding affinity.

Conclusions:

• Plk4 acts as its own kinase to generate its degradation signal.
• Autophosphorylation is a key mechanism controlling Plk4 stability and centriole duplication.
• Plk4 self-regulation ensures precise control over centriole biogenesis.