Crystal structure of human XLF/Cernunnos reveals unexpected differences from XRCC4 with implications for NHEJ

Yi Li, Dimitri Y Chirgadze, Victor M Bolanos-Garcia, Bancinyane L Sibanda, Owen R Davies, Peter Ahnesorg, Stephen P Jackson, Tom L Blundell

Research output: Contribution to journalArticlepeer-review

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 Å 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.
Original languageEnglish
Pages (from-to)290-300
Number of pages11
JournalEMBO Journal
Volume27
Issue number1
Early online date29 Nov 2007
DOIs
Publication statusE-pub ahead of print - 29 Nov 2007

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