Delineation of the Xrcc4-interacting region in the globular head domain of cernunnos/XLF

Abstract

In mammals, the majority of DNA double-strand breaks are processed by the nonhomologous end-joining (NHEJ) pathway, composed of seven factors: Ku70, Ku80, DNA-PKcs, Artemis, Xrcc4 (X4), DNA-ligase IV (L4), and Cernunnos/XLF. Cernunnos is part of the ligation complex, constituted by X4 and L4. To improve our knowledge on the structure and function of Cernunnos, we performed a systematic mutagenesis study on positions selected from an analysis of the recent three-dimensional structures of this factor. Ten of 27 screened mutants were non-functional in several DNA repair assays. Outside amino acids critical for the expression and stability of Cernunnos, we identified three amino acids (Arg64, Leu65, and Leu115) essential for the interaction with X4 and the proper function of Cernunnos. Docking the crystal structures of the two factors further validated this probable interaction surface of Cernunnos with X4. © 2010 by The American Society for Biochemistry and Molecular Biology, Inc.