DNA Double-Strand Break Repair: A Relentless Hunt Uncovers New Prey

A major pathway for repair of DNA double-strand breaks is nonhomologous end-joining (NHEJ). In this issue of Cell, Buck et al. (2006a) and Ahnesorg et al. (2006) report the discovery of a new NHEJ factor called Cernunnos-XLF. Both groups report that this protein is mutated in a rare inherited human syndrome characterized by severe immunodeficiency, developmental delay, and hypersensitivity to agents that cause DNA double-strand breaks