Holliday junction-binding activity of human SPF45.

Area of Science:

• Molecular Biology
• Genetics
• Biochemistry

Background:

• SPF45 is a bifunctional protein involved in both RNA splicing and DNA repair.
• Previous studies suggested SPF45's role in DNA repair via homologous recombination, linked to RAD51-family proteins.

Purpose of the Study:

• To investigate the function of human SPF45 in homologous recombination DNA repair.
• To biochemically characterize the interaction of SPF45 with DNA structures and RAD51 proteins.

Main Methods:

• Purification of human SPF45 protein.
• DNA binding assays using Holliday junctions and other DNA structures.
• Deletion analysis and alanine-scanning mutagenesis of SPF45.
• Co-immunoprecipitation assays to study protein-protein interactions.

Main Results:

• Human SPF45 preferentially binds to Holliday junctions, a critical intermediate in homologous recombination.
• The RNA recognition motif (RRM) in the C-terminus is not essential for DNA binding.
• N-terminal lysine residues are implicated in Holliday junction binding.
• SPF45 shows significant binding to RAD51B and lower affinity binding to RAD51 and DMC1.

Conclusions:

• Biochemical evidence supports a role for human SPF45 in DNA repair through the homologous recombination pathway.
• SPF45 interacts with key components of the homologous recombination machinery, including RAD51 paralogs.