Centromeric binding and activity of Protein Phosphatase 4

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• The cell division cycle depends on precise regulation of protein phosphorylation and dephosphorylation.
• Understanding how multimeric protein phosphatases are targeted to specific cellular locations by regulatory subunits is crucial for elucidating their cell cycle roles.
• Phosphoprotein phosphatase 4 (PP4) has emerged as a key regulator of cell cycle progression.

Purpose of the Study:

• To investigate the mechanism by which the regulatory subunit of Drosophila PP4, Falafel (Flfl), targets the enzyme to its site of action.
• To characterize the interaction between Flfl and centromeric protein C (CENP-C) and its functional significance during mitosis.

Main Methods:

• Crystal structure determination of the Flfl EVH1 domain bound to a CENP-C peptide.
• Biochemical assays to assess the interaction between Flfl and CENP-C.
• Functional studies in Drosophila to evaluate the role of Flfl-CENP-C binding in maintaining centromeric proteins during mitosis.

Main Results:

• The EVH1 domain of Flfl directly interacts with CENP-C, revealing a novel target-recognition mode distinct from proline-rich ligand binding.
• Structural analysis elucidated the atomic details of the Flfl EVH1 domain-CENP-C interaction.
• Flfl binding to CENP-C is essential for recruiting PP4 activity to centromeres, thereby stabilizing CENP-C and associated kinetochore proteins during mitosis.

Conclusions:

• The study identifies a new mechanism for targeting protein phosphatases to centromeres via the Flfl-CENP-C interaction.
• This interaction plays a critical role in ensuring proper chromosome segregation by maintaining kinetochore integrity during cell division.
• The findings provide insights into the regulation of protein phosphatase activity and its importance in cell cycle control.