Regulation of autophosphorylation controls PLK4 self-destruction and centriole number

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Polo-like kinase 4 (PLK4) is essential for centriole biogenesis, with its absence preventing centriole formation and excess leading to amplification.
• The SCF-Slimb/βTrCP E3 ubiquitin ligase complex regulates PLK4 levels by targeting a specific phosphodegron for degradation, a process typically controlled by phosphorylation cascades.

Purpose of the Study:

• To elucidate the mechanism by which PLK4 levels are regulated.
• To investigate the role of PLK4 autophosphorylation in its degradation and centriole number control.

Main Methods:

• Investigated PLK4 autophosphorylation using biochemical assays.
• Analyzed the impact of specific phosphorylation sites (Ser293, Thr297) on PLK4 degradation and SCF-Slimb/βTrCP binding.
• Examined the role of a phospho-cluster outside the degron in regulating PLK4 activity and centriole number.

Main Results:

• PLK4 functions as a suicide kinase, undergoing multisite trans-autophosphorylation on critical residues within its degron (Ser293, Thr297).
• Ser293 phosphorylation is critical for SCF-Slimb/βTrCP binding and degradation, while Thr297 phosphorylation maximizes auto-destruction.
• Autophosphorylation of a phospho-cluster outside the degron regulates Thr297 phosphorylation, PLK4 degradation, and ultimately centriole number.

Conclusions:

• PLK4 degradation is tightly regulated by a sequential trans-autophosphorylation mechanism, ensuring proper centriole duplication.
• Dysregulation of PLK4-Slimb/βTrCP interaction impacts both somatic and germline cells, with implications for cancer.
• This study reveals novel connections between centriole number control, PLK4 regulation, and tumorigenesis.