SSBP4 is a single-stranded DNA-binding protein that functions as a key component of the architectural LDB1 complex, which mediates chr19 looping and transcriptional regulation 1. SSBP4 belongs to an evolutionarily conserved gene family with putative sequence-specific single-stranded DNA-binding activity 2. Structurally, SSBP4 contains a conserved N-terminal LUFS domain that mediates protein-protein interactions; related family members form tetramers through this domain, suggesting SSBP4 likely possesses similar oligomerization capacity 3. While SSBP3 is the functionally essential SSBP family member for erythroid cell viability and LDB1-dependent chr19 looping 1, SSBP4 colocalizes with LDB1 genome-wide and contributes to the architectural complex's function. Genetically, rs7257932 in SSBP4 is a functional variant associated with breast cancer susceptibility that modulates promoter activity 4. Additionally, CpG sites near SSBP4 show epigenome-wide significant associations with maternal prenatal stress and cortisol levels in neonatal saliva, suggesting potential involvement in stress-responsive developmental programming 5. The gene maps to chromosome 19.1 2.