Mapping intramolecular interactions between domains in HMGB1 using a tail-truncation approach

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• High Mobility Group Box 1 (HMGB1) is a nuclear protein involved in DNA binding and chromatin remodeling.
• The C-terminal acidic tail of HMGB1 is known to negatively regulate its DNA-binding activity, but the precise mechanism remains unclear.

Purpose of the Study:

• To elucidate the mechanism by which the acidic C-terminal tail of HMGB1 negatively regulates DNA interaction.
• To investigate the structure-function relationship between HMGB1 tail length and DNA-binding affinity.

Main Methods:

• Nuclear Magnetic Resonance (NMR) chemical-shift perturbation (CSP) mapping was employed.
• A series of HMGB1 tail-truncation mutants with incremental deletions were generated.
• CSP mapping was used to analyze the interactions between the tail and the HMG-box DNA-binding domains.

Main Results:

• Tails of varying lengths exhibit differential binding affinities to the HMG boxes.
• Truncated tails bind along the same path on the HMG boxes as the full-length tail, with length influencing the "reach" of the tail.
• The HMGB1 tail establishes extensive contacts with the DNA-binding surfaces of both HMG boxes.

Conclusions:

• The extensive contacts between the HMGB1 tail and the HMG boxes' DNA-binding surfaces explain the tail's negative regulatory role.
• Tail length is a critical determinant of HMGB1's DNA-binding affinity and regulatory function.
• This study provides novel insights into the structural basis of HMGB1-DNA interaction regulation.