All three B cell-specific activities of the immunoglobulin (Ig) gene re-modeling system-gene conversion, somatic hypermutation and class switch recombination-require activation-induced deaminase (AID). AID-induced DNA lesions must be further processed and dissected into different DNA recombination pathways. In order to characterize potential intermediates for Ig gene conversion, we inserted an I-SceI recognition site into the complementarity determining region 1 (CDR1) of the Ig light chain locus of the AID knockout DT40 cell line, and conditionally expressed I-SceI endonuclease. Here, we show that a double-strand break (DSB) in CDR1 is sufficient to trigger Ig gene conversion in the absence of AID. The pattern and pseudogene usage of DSB-induced gene conversion were comparable to those of AID-induced gene conversion; surprisingly, sometimes a single DSB induced multiple gene conversion events. These constitute direct evidence that a DSB in the V region can be an intermediate for gene conversion. The fate of the DNA lesion downstream of a DSB had more flexibility than that of AID, suggesting two alternative models: (i) DSBs during the physiological gene conversion are in the minority compared to single-strand breaks (SSBs), which are frequently generated following DNA deamination, or (ii) the physiological gene conversion is mediated by a tightly regulated DSB that is locally protected from non-homologous end joining (NHEJ) or other non-homologous DNA recombination machineries.
A double-strand break can trigger immunoglobulin gene conversion / G. Bastianello, H. Arakawa. - In: NUCLEIC ACIDS RESEARCH. - ISSN 0305-1048. - 45:1(2017), pp. 231-243.
|Titolo:||A double-strand break can trigger immunoglobulin gene conversion|
BASTIANELLO, GIULIA (Primo)
|Settore Scientifico Disciplinare:||Settore BIO/11 - Biologia Molecolare|
|Data di pubblicazione:||2017|
|Data ahead of print / Data di stampa:||3-ott-2016|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1093/nar/gkw887|
|Appare nelle tipologie:||01 - Articolo su periodico|
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