Crystal structure of the Xrcc4 DNA repair protein and implications for end joining

AUTOR(ES)

Junop, Murray S.

FONTE

Oxford University Press

RESUMO

XRCC4 is essential for carrying out non-homologous DNA end joining (NHEJ) in all eukaryotes and, in particular, V(D)J recombination in vertebrates. Xrcc4 protein forms a complex with DNA ligase IV that rejoins two DNA ends in the last step of V(D)J recombination and NHEJ to repair double strand breaks. XRCC4-defective cells are extremely sensitive to ionizing radiation, and disruption of the XRCC4 gene results in embryonic lethality in mice. Here we report the crystal structure of a functional fragment of Xrcc4 at 2.7 Å resolution. Xrcc4 protein forms a strikingly elongated dumb-bell-like tetramer. Each of the N-terminal globular head domains consists of a β-sandwich and a potentially DNA-binding helix– turn–helix motif. The C-terminal stalk comprising a single α-helix >120 Å in length is partly incorporated into a four-helix bundle in the Xrcc4 tetramer and partly involved in interacting with ligase IV. The Xrcc4 structure suggests a possible mode of coupling ligase IV association with DNA binding for effective ligation of DNA ends.

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