Translocation of an antibody transgene requires AID and occurs by interchromosomal switching to all switch regions except the mu switch region

Abstract

Summary Immunoglobulin (Ig) class switch recombination (CSR) occurs most often by intrachromosomal recombinations between switch (S) regions located on a single chromosome, but can also occur by interchomosomal recombinations between Ig heavy chain (Igh) S regions located on chomosomal homologs. Interchromosomal recombinations have also been found between chromosomes that are not homologs; examples are Igh/c-myc and Igh/transgene translocations. Most, but not all, studies have indicated that activation-induced cytidine deaminase (AID) is important in Igh/c-myc translocations. The role of AID has not been determined for Igh/transgene translocations. We now show that the majority of Igh/transgene translocations between non-homologs from an Ig transgenic mouse are dependent on AID, but we also find a small number of these translocations that can occur in the absence of AID. Surprisingly, our results also indicate that, even though Sγ switch sequences in the endogenous Igh locus participate in chromosomal translocations with the non-homolog transgene-bearing chromosome, Sμ switch sequences do not. This contrasts with the fact that both endogenous Sμ and Sγ sequences participate in intrachromosomal CSR. Our findings suggest the operation of a regulatory mechanism that can differentially control the accessibility of Sμ and Sγ regions for non-homolog translocations even when both are accessible for intrachromosomal recombination.

Alternative end-joining pathway(s): Bricolage at DNA breaks

“…Concomitantly to the finding that PARP inhibitors increase the sensitivity of DNA-PK-deficient cells to radiomimetic-induced DSBs [45], biochemical experiments [45,48,49] and plasmid assays in Kudeficient cells [61] substantiated the involvement of PARP1 in a non [62,71,82,95,100,116,118,[149][150][151][152]154,160,161,163,168,169,171,174,180,182,184,185,264,[305][306][307] Translocation IR, etoposide, Zn-finger nucleases [94,240,245,303,308] RAG, AID, spontaneous [62,95,100,152,154,162,163,171,240,261,269,…”

“…This may also reflect a form of coupling between AID-mediated cleavage and the C-NHEJ machinery, although less stringent than between RAG-induced DSBs and C-NHEJ. This notion is further supported by the different ability of S compared to other S regions to participate in translocations [269]. Alternatively, the mechanism of production of DSBs, by affecting the nature of DNA ends, may influence the way they are processed by the A-EJ machinery, thus giving rise to more or less MH at the junction.…”

Rabbits transgenic for human IgG genes recapitulating rabbit B-cell biology to generate human antibodies of high specificity and affinity

“…Although to date we have not elucidated the mechanism, possible explanations include cis-recombination and interallelic class-switch recombination, which might point to a selection pressure of a particular immunological check point at the IgG Fc part during the rabbit B-cell cycle. [32][33][34][35][36][37][38][39] The analysis of the VDJ sequence in the transgenic rabbits revealed that approximately 82% of all sequences are correctly joined together, delivering a human huVH-D-huJH sequence. In matured IgG antibodies, the original rabbit-derived DH sequence is highly altered and quite antibody-specific so that it can hardly be assigned to a specific rabbit (or human) DH germline sequence.…”

Transgenes of the Mouse Immunoglobulin Heavy Chain Locus, Lacking Distal Elements in the 3′ Regulatory Region, Are Impaired for Class Switch Recombination

“…Even though some recombination events take place in switch regions [32], others can take place even if donor transgenes lack switch regions [33]. Even though the majority of the recombination events require AID, a portion of the trans-recombination events may be independent of AID [36]. It seems likely that the final products of trans-recombination arise from multiple recombination pathways [32], [33], [36].…”

“…Even though the majority of the recombination events require AID, a portion of the trans-recombination events may be independent of AID [36]. It seems likely that the final products of trans-recombination arise from multiple recombination pathways [32], [33], [36].…”