Download MendeleyCrystal structure of human XLF/Cernunnos reveals unexpected differences from XRCC4 with implications for NHEJ.
Li, Y., Chirgadze, D.Y., Bolanos-Garcia, V.M., Sibanda, B.L., Davies, O.R., Ahnesorg, P., Jackson, S.P., Blundell, T.L.(2008) EMBO J 27: 290-300
- PubMed: 18046455
- DOI: https://doi.org/10.1038/sj.emboj.7601942
- Primary Citation of Related Structures:
2QM4 - PubMed Abstract:
The recently characterised 299-residue human XLF/Cernunnos protein plays a crucial role in DNA repair by non-homologous end joining (NHEJ) and interacts with the XRCC4-DNA Ligase IV complex. Here, we report the crystal structure of the XLF (1-233) homodimer at 2.3 A resolution, confirming the predicted structural similarity to XRCC4. The XLF coiled-coil, however, is shorter than that of XRCC4 and undergoes an unexpected reverse in direction giving rise to a short distorted four helical bundle and a C-terminal helical structure wedged between the coiled-coil and head domain. The existence of a dimer as the major species is confirmed by size-exclusion chromatography, analytical ultracentrifugation, small-angle X-ray scattering and other biophysical methods. We show that the XLF structure is not easily compatible with a proposed XRCC4:XLF heterodimer. However, we demonstrate interactions between dimers of XLF and XRCC4 by surface plasmon resonance and analyse these in terms of surface properties, amino-acid conservation and mutations in immunodeficient patients. Our data are most consistent with head-to-head interactions in a 2:2:1 XRCC4:XLF:Ligase IV complex.
Organizational Affiliation:
Department of Biochemistry, University of Cambridge, Cambridge, UK. jessica@cryst.bioc.cam.ac.uk
