A novel TPR-BEN domain interaction mediates PICH-BEND3 association

Area of Science:

• Molecular Biology
• Cell Biology
• Biochemistry

Background:

• PICH (Plk1-interacting checkpoint helicase) is vital for human chromosome stability.
• PICH collaborates with topoisomerase IIα to prevent chromosome missegregation by resolving ultra-fine anaphase bridges (UFBs).

Purpose of the Study:

• To identify novel interaction partners of PICH during mitosis.
• To characterize the molecular interaction between PICH and its newly identified partner, BEND3.

Main Methods:

• Co-immunoprecipitation assays to identify PICH interaction partners.
• Protein purification of full-length PICH and BEND3.
• In vitro biochemical interaction assays.
• X-ray crystallography to determine the structure of the PICH TPR-BEND3 BEN domain complex.
• Site-directed mutagenesis to identify key amino acids in the interaction.

Main Results:

• BEND3 was identified as a novel interaction partner of PICH in human mitotic cells.
• PICH and BEND3 exhibit a functional biochemical interaction in vitro.
• The interaction involves a novel interface between PICH's TPR domain and BEND3's BEN domain.
• The crystal structure of the PICH TPR-BEN complex was determined at 2.2 Å resolution.
• Key amino acids mediating the interaction were identified through structural and functional analyses.

Conclusions:

• BEND3 interacts with PICH through a unique TPR-BEN domain interface.
• This interaction suggests a new function for BEND3 in association with PICH.
• This study presents the first example of a specific protein-protein interaction mediated by a BEN domain.