SFR1 (SWI5 dependent homologous recombination repair protein 1) functions as a key component of DNA repair and transcriptional regulation mechanisms. As part of the SWI5-SFR1 complex, SFR1 facilitates double-strand break repair via homologous recombination by stabilizing Rad51-ssDNA presynaptic filaments, which are essential for DNA strand invasion during repair 1. The complex demonstrates a 1:1 stoichiometry and requires both subunits for optimal Rad51 stimulation and homologous DNA pairing activity 1. SFR1 cooperatively interacts with other auxiliary factors like Rad55-Rad57 to enhance Rad51 function through multiple binding sites within its intrinsically disordered N-terminus 2. Beyond DNA repair, SFR1 serves as a transcriptional modulator for estrogen receptor alpha (ERα), physically interacting with ERα in the nucleus and potentiating both ligand-dependent and ligand-independent transcriptional activity 3. SFR1 occupies ER binding sites on target gene promoters and influences ER-dependent cancer cell proliferation 3. Recent multi-omics studies have identified SFR1 as a potential therapeutic target for idiopathic pulmonary fibrosis, with downregulation observed in disease tissue 4. The protein's dual roles in genome stability and gene regulation highlight its importance in cellular homeostasis.