Identification of a triplex DNA-binding protein from human cells

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• Triple helix DNA structures, formed by intramolecular or intermolecular interactions, are recognized by specific proteins.
• These proteins stabilize triplex structures and may be involved in gene regulation processes.
• Identifying proteins that bind to triple helix DNA is crucial for understanding their biological functions.

Purpose of the Study:

• To identify proteins that specifically bind to and stabilize DNA triple helix structures.
• To investigate the role of these proteins in potential gene regulation mechanisms.

Main Methods:

• Design and synthesis of a 55-nucleotide DNA oligomer capable of forming an intramolecular Py Pu x Py triple helix.
• Validation of triplex stability under physiological conditions using gel retardation and thermal denaturation assays.
• Identification and characterization of a DNA-binding protein from HeLa cell nuclear extracts using electrophoretic mobility shift assays (EMSA).

Main Results:

• A protein with an apparent molecular mass of 55 kDa was identified that binds to the synthetic DNA triple helix oligonucleotide.
• EMSA demonstrated that this protein lacks affinity for single-stranded (third strand) and double-stranded (Watson-Crick duplex) DNA.
• The protein exhibits binding to an intramolecular Py Pu x Pu triplex, albeit with lower affinity compared to the Py Pu x Py triplex.

Conclusions:

• A specific DNA triple helix-binding protein of 55 kDa has been identified in HeLa cells.
• This protein selectively recognizes and binds to triple helix DNA structures, distinguishing them from single and double helices.
• The findings suggest a role for this protein in the stabilization and potential regulation of gene expression involving DNA triplexes.