Double stranded DNA breaks (DSB's) are the most toxic of DNA lesions. They occur in response to genotoxic stress, and they are also an obligate intermediate in the V(D)J recombination events in the immune system. The mechanism by which cells deal with DSB's is known as NHEJ (non-homologous end-joining), and involves a core group of proteins that includes Ku, DNA-PK, XRCC4, and XLF (1). XLF, also known as Cernunnos, was originally discovered as a mutated protein from cells of individuals who displayed features of growth retardation, microcephaly, and immunodeficiency (2). These cells were sensitive to ionizing radiation and defective in V(D)J recombination. Exogenous expression of wild type XLF corrected these deficiencies (3), indicating that XLF is a critical component of the NHEJ response. XLF physically interacts with and may stimulate the ligase activity of XRCC4 (3). Applications: Suitable for use in Western Blot and Immunoprecipitation. Other applications not tested. Recommended Dilution: Western Blot: 1:1000, incubate membrane with diluted primary antibody in 5% BSA, 1X TBS, 0.1% Tween 20 at 4°C with gentle shaking, overnight., Immunoprecipitation: 1:100, Optimal dilutions to be determined by the researcher. Storage and Stability: May be stored at 4°C for short-term only. Aliquot to avoid repeated freezing and thawing. Store at -20°C. Aliquots are stable for 12 months. For maximum recovery of product, centrifuge the original vial after thawing and prior to removing the cap.