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Nucleic Acids Res. 2012 Sep 1;40(17):8381-91. Epub 2012 Jun 27.

Terminal deoxynucleotidyl transferase requires KU80 and XRCC4 to promote N-addition at non-V(D)J chromosomal breaks in non-lymphoid cells.

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Institut Pasteur, CNRS URA 2581, 25 rue du Dr. Roux 75724 Paris, France.


Terminal deoxynucleotidyl transferase (TdT) is a DNA polymerase that increases the repertoire of antigen receptors by adding non-templated nucleotides (N-addition) to V(D)J recombination junctions. Despite extensive in vitro studies on TdT catalytic activity, the partners of TdT that enable N-addition remain to be defined. Using an intrachromosomal substrate, we show here that, in Chinese hamter ovary (CHO) cells, ectopic expression of TdT efficiently promotes N-additions at the junction of chromosomal double-strand breaks (DSBs) generated by the meganuclease I-SceI and that the size of the N-additions is comparable with that at V(D)J junctions. Importantly, no N-addition was observed in KU80- or XRCC4-deficient cells. These data show that, in a chromosomal context of non-lymphoid cells, TdT is actually able to promote N-addition at non-V(D)J DSBs, through a process that strictly requires the components of the canonical non-homologous end-joining pathway, KU80 and XRCC4.

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