PLK1-mediated phosphorylation cascade activates Mis18 complex to ensure centromere inheritance.

Area of Science:

• Cell Biology
• Epigenetics
• Molecular Biology

Background:

• Accurate chromosome segregation depends on microtubule attachment to centromeres, marked by CENP-A.
• CENP-A nucleosomes are diluted during DNA replication, necessitating restoration for centromere identity.
• The Mis18 complex (Mis18α-Mis18β-Mis18BP1) orchestrates cell cycle-controlled CENP-A restoration.

Purpose of the Study:

• To elucidate the molecular mechanism by which PLK1 interacts with the Mis18 complex.
• To investigate the role of Mis18 complex phosphorylation in CENP-A loading and centromere inheritance.

Main Methods:

• Co-immunoprecipitation assays to detect PLK1-Mis18 complex interaction.
• Site-directed mutagenesis to disrupt Mis18α and Mis18BP1 phosphorylation sites.
• Biochemical and functional analyses of CENP-A loading and HJURP recruitment.

Main Results:

• PLK1 binds the Mis18 complex via its Polo-box domain, recognizing specific phosphorylation sites on Mis18α and Mis18BP1.
• Disruption of these phosphorylation sites impairs HJURP recruitment and CENP-A loading at centromeres.
• Phosphorylation of Mis18α and PLK1 binding are essential for Mis18 complex activation and HJURP interaction.

Conclusions:

• PLK1 acts as a licensing factor for centromere inheritance by phosphorylating the Mis18 complex.
• This phosphorylation event is critical for the recruitment of HJURP and the subsequent loading of new CENP-A.
• The study reveals key molecular events in maintaining centromere identity and ensuring accurate chromosome segregation.