Oligonucleotide/Oligosaccharide Binding Fold Containing Protein 2B (OBFC2B)

SSB1 bound specifically to ssDNA, in particular to polypyrimidines, and that the binding affinity increased significantly with the length of the DNA substrate. ATM interacted with SSB1 and phosphorylated it on thr117 in response to DNA double-strand breaks, and this phosphorylation stabilized SSB1 against degradation by the proteasome. Upon induction of DNA damage, SSB1 accumulated in the nucleus, where it colocalized at distinct foci with DNA damage repair proteins. Deletion of SSB1 abrogated the cellular response to radiation-induced DNA double-strand breaks, including activation of ATM and phosphorylation of ATM targets. Cells deficient in SSB1 exhibited increased radiosensitivity, defective checkpoint activation, and enhanced genomic instability coupled with a diminished capacity for DNA repair.