NABP1 (nucleic acid binding protein 1) is a single-stranded DNA binding protein that functions as a component of the SOSS complex, a multiprotein assembly operating downstream of the MRN complex to promote DNA repair and G2/M checkpoint control 1. NABP1 contains a conserved oligonucleotide-binding (OB) fold domain responsible for ssDNA recognition, particularly of polypyrimidine sequences, and a flexible C-terminal extension mediating protein-protein interactions 2. The protein recognizes UV-damaged DNA structures, including cyclobutane pyrimidine dimers, through four key aromatic residues within its OB domain 3. NABP1 is essential for efficient homologous recombination-dependent repair of double-strand breaks and ATM-dependent signaling, thereby maintaining genomic stability. Clinically, NABP1 dysregulation is implicated in multiple malignancies. In hepatocellular carcinoma post-TACE treatment, elevated NABP1+ malignant hepatocytes correlate with poor treatment response and dismal prognosis 4. NABP1 expression can be suppressed by miR-26a-5p, creating a homologous recombination repair defect (HRD) phenotype that enhances chemotherapy sensitivity in triple-negative breast cancer 5. Additionally, NABP1 genetic variants are associated with laryngeal squamous cell carcinoma patient survival outcomes 6, and NABP1 fusions occur as rare variants in acute promyelocytic leukemia 7.