Distorted DNA structures induced by HMGB2 possess a high affinity for HMGB2

Area of Science:

• Molecular Biology
• Biochemistry
• Structural Biology

Background:

• High mobility group box 2 (HMGB2) protein is known to bind DNA non-specifically, influencing DNA structure.
• DNA cyclization assays are used to study DNA bending and protein-DNA interactions.

Purpose of the Study:

• To investigate the nature of unidentified DNA bands observed during HMGB2-induced DNA cyclization.
• To characterize the DNA structures and HMGB2 complexes formed and elucidate the role of HMGB2 domains.

Main Methods:

• DNA cyclization assays were performed with HMGB2 protein.
• Gel electrophoresis, re-electrophoresis, and proteinase K digestion were used to analyze DNA-protein complexes.
• Binding affinities (K(d)) were determined for HMGB2 with different DNA forms.

Main Results:

• Two novel HMGB2-DNA complexes, alpha and beta, were identified, containing circularized DNA with higher affinity for HMGB2.
• These DNA components exhibited distorted structures with partial single-stranded regions and nicks, suggesting severe DNA distortion.
• The acidic C-tail of HMGB2 was found to be essential for inducing these unique distorted DNA structures.

Conclusions:

• HMGB2 induces peculiar, high-affinity DNA structures that are distinct from its DNA-bending activity alone.
• These distorted DNA structures, mediated by the HMGB2 C-tail, may play a significant role in HMGB2's biological functions.
• The findings suggest HMGB2's involvement in processes like nucleosome binding and DNA organization through structural manipulation.