K63-linked polyubiquitin chains bind to DNA to facilitate DNA damage repair

Area of Science:

• Biochemistry
• Molecular Biology
• Cell Biology

Background:

• Polyubiquitylation typically regulates protein stability and interactions.
• The function of polyubiquitin chains beyond protein modification is largely unexplored.

Purpose of the Study:

• To investigate potential non-protein-related functions of polyubiquitin chains.
• To determine if polyubiquitin chains interact with DNA and if this interaction has functional significance.

Main Methods:

• In vitro pull-down assays using synthetic materials.
• Identification of a specific motif (DNA-interacting patch - DIP) on ubiquitin.
• Analysis of mutant ubiquitin's DNA binding and cellular DNA repair capacity.

Main Results:

• Lys63-linked polyubiquitin chains bind to DNA through a conserved motif (DIP: Thr9, Lys11, Glu34).
• DNA damage enhances this binding, facilitating the recruitment of repair factors via the Ile44 patch.
• Mutations in the DIP impair DNA binding, reduce polyubiquitin chain accumulation at damage sites, and compromise DNA repair.

Conclusions:

• Lys63-linked polyubiquitin chains possess a direct DNA-binding function.
• This DNA interaction is essential for efficient DNA damage repair.
• The DIP motif is critical for ubiquitin's role in DNA repair pathways.