A methylation-phosphorylation switch determines Plk1 kinase activity and function in DNA damage repair

Area of Science:

• Cell Biology
• Molecular Biology
• Biochemistry

Background:

• Polo-like kinase 1 (Plk1) is vital for cell cycle progression.
• The precise mechanisms regulating Plk1 activity remain incompletely understood.

Purpose of the Study:

• To investigate the role of post-translational modifications in Plk1 regulation.
• To elucidate the interplay between Plk1 methylation and phosphorylation.

Main Methods:

• Site-directed mutagenesis to create Plk1 mutants (K209A, K209M).
• Analysis of Plk1 activity, cell cycle progression, and DNA damage response in wild-type and mutant cells.
• Detection of Plk1 methylation levels (Plk1 K209me1) under stress conditions.

Main Results:

• G9a-mediated monomethylation of Plk1 at Lys209 antagonizes T210 phosphorylation, inhibiting Plk1 activity.
• Plk1 K209A mutants exhibit DNA replication defects, while K209M mutants show prolonged metaphase-anaphase transition due to failed sister chromatid separation.
• Accumulation of Plk1 K209me1 occurs under DNA damage stress, and its absence delays RPA2 and RAD51 removal from damage sites.

Conclusions:

• Plk1 activity is controlled by a methylation-phosphorylation switch involving G9a and Lys209.
• This switch is critical for proper DNA replication, sister chromatid separation, and DNA damage repair.
• Plk1 methylation plays a key role in guiding DNA damage repair machinery.