Mutations, duplication, and deletion of recombined switch regions suggest a role for DNA replication in the immunoglobulin heavy-chain switch.

Dunnick, Wesley A.; Wilson, Marcus D.; Stavnezer, Janet

doi:10.1128/mcb.9.5.1850

Cited by 86 publications

(79 citation statements)

References 25 publications

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“…One possibility we consider envisions the Ighm/ c-myc exchange in a mature, class switch competent Bcell that has encountered antigen and other appropriate signals and prepares itself for isotype switching. In this situation, the initial lesion that provokes illegitimate recombination between Ighm and c-myc may be a DNA double-strand break in Sm due to internal rearrangements of Sm, mostly deletions and occasionally inversions, known to occur prior to class switching (Radbruch et al, 1986;Dunnick et al, 1989). The interruption of Sm may lead to Ighm/c-myc recombination and chromosomal translocation t(12;15) on the non-productive Igh allele, followed by deletional remodeling' of the t(12;15) by aberrant class switch recombination and normal class switching on the productive Igh allele (see Figure 7 for more details).…”

Section: Discussionmentioning

confidence: 99%

Deletional remodeling of c-myc-deregulating chromosomal translocations

1997

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Evidence is presented for the existence of a novel remodeling-by-deletion mechanism that alters the ®ne structure of c-myc-deregulating chromosomal translocations in t(12;15)-positive BALB/c plasmacytomas. DNA sequence analysis of the t(12;15) in ®ve primary tumors revealed the co-existence of precursor cells harboring genetic recombinations between the immunoglobulin heavy-chain m locus (Ighm) and c-myc with clonally related progenitors containing rearrangements between the immunoglobulin heavy-chain a locus (Igha) and cmyc. Clonal relatedness was based upon unique junction fragments between the switch region of Ighm and c-myc. Sm/c-myc junctions are thus useful clonotypic markers for monitoring the conversion of Ighm/c-myc-positive tumor precursor clones into Igha/c-myc-positive plasmacytomas. Aberrant isotype switch recombination appears to be the most likely mechanism e ecting this conversion event (other possibilities are discussed) which may help to explain the preferred usage of the Igha locus in recombinations with c-myc in t(12;15)-positive plasma cell tumors in BALB/c mice.

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Section: Discussionmentioning

confidence: 99%

Deletional remodeling of c-myc-deregulating chromosomal translocations

1997

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“…The observation that the 5Ј-C /cmyc exchanges were accompanied invariably by large deletions in S was consistent with this hypothesis, since S deletions are common in B cells undergoing isotype switching. 14,15 Furthermore, the average length of deletions in S was 2.7 kb and thus considerably longer than the average deletion in c-myc, which was just 171 bp (calculated from Table 2, last two columns). This suggested that S was targeted by a deletional mechanism (switch recombinase?)…”

Section: Mechanism Of the 5ј-c /C-myc Exchangementioning

confidence: 91%

Lymph nodes and Peyer's patches of IL-6 transgenic BALB/c mice harbor T(12;15) translocated plasma cells that contain illegitimate exchanges between the immunoglobulin heavy-chain μ locus and c-myc

2000

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“…5c; P = 0.0015, χ 2 test, 31 mutations in 166 hot-spot nucleotides compared with 21 mutations in 284 nonhot-spot nucleotides). Hypermutation has also been reported in BCL-6 (refs 24, 25) and in areas adjoining switch joints 26 , but the relationship of these mutations to the switch recombination reaction has never been determined. Our experiments show that the Sμ lesions are inducible, that they are Sμ specific because they are not found in adjacent DNA, that the lesions precede CSR, and that they are AID dependent.…”

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confidence: 99%

AID is required to initiate Nbs1/γ-H2AX focus formation and mutations at sites of class switching

Petersen

Casellas

Reina‐San‐Martin

et al. 2001

Nature

460

437

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Class switch recombination (CSR) is a region-specific DNA recombination reaction that replaces one immunoglobulin heavy-chain constant region (CH) gene with another. This enables a single variable (V) region gene to be used in conjunction with different downstream CH genes, each having a unique biological activity. The molecular mechanisms that mediate CSR have not been defined, but activation-induced cytidine deaminase (AID), a putative RNA-editing enzyme, is required for this reaction 1 . Here we report that the Nijmegen breakage syndrome protein (Nbs1) and phosphorylated H2A histone family member X (γ-H2AX, also known as γ-H2afx), which facilitate DNA double-strand break (DSB) repair 2-4 , form nuclear foci at the CH region in the G1 phase of the cell cycle in cells undergoing CSR, and that switching is impaired in H2AX -/-mice. Localization of Nbs1 and γ-H2AX to the IgH locus during CSR is dependent on AID. In addition, AID is required for induction of switch region (Sμ)-specific DNA lesions that precede CSR. These results place AID function upstream of the DNA modifications that initiate CSR.Correspondence and requests for materials should be addressed to A.N. (andre_nussenzweig@nih.gov) or M.C.N. (nussen@mail.rockefeller.edu).. Supplementary Information accompanies the paper on Nature's website (http://www.nature.com). Competing interests statementThe authors declare that they have no competing financial interests. To determine whether DNA repair factors associate with DSBs at the switch regions, we first examined the intracellular localization of γ-H2AX, Nbs1, Rad51 and Brca1 in activated B cells by immunofluorescence. Brca1 and Rad51 are required for homologous recombination, the Mre11-Rad50-Nbs1 complex has been implicated in both homologous recombination and non-homologous end-joining (NHEJ), and γ-H2AX is critical for recruiting these repair factors to DSBs 6 and facilitates NHEJ in Saccharomyces cerevisiae 4 . All four proteins showed diffuse nuclear staining in most of the resting B cells from C57BL/6 wild-type mice. High local concentrations of these factors (nuclear foci) were detected in a very small percentage of cells (<5%), which increased significantly when the cells were stimulated to undergo CSR in vitro with lipopolysaccharide (LPS) and interleukin (IL)-4 (Fig. 1a). After 3 days of stimulation, 37% of the B cells contained discrete Brca1 foci (12 ± 6 per cell) and 43% contained Rad51 foci (7 ± 3 per cell), consistent with previous results 7 ; the remaining cells exhibited a weak, diffuse pattern of nuclear staining (Fig. 1a). Many of the stimulated B cells also formed Nbs1 foci (32% contained, on average, 3 ± 2 per cell) and γ-H2AX foci (40% contained, on average, 4.5 ± 3 per cell). To determine which of these repair factors are co-localized in activated B cells, we performed two colour immunofluoresence experiments (Fig. 1b). Only 20% of the cells that contained Rad51 and Nbs1 (n = 687) or Brca1 and Nbs1 foci (n = 431) exhibited co-localization. In contrast, γ-H2AX foci co-localiz...

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Mutations, duplication, and deletion of recombined switch regions suggest a role for DNA replication in the immunoglobulin heavy-chain switch.

Cited by 86 publications

References 25 publications

Deletional remodeling of c-myc-deregulating chromosomal translocations

Deletional remodeling of c-myc-deregulating chromosomal translocations

Lymph nodes and Peyer's patches of IL-6 transgenic BALB/c mice harbor T(12;15) translocated plasma cells that contain illegitimate exchanges between the immunoglobulin heavy-chain μ locus and c-myc

AID is required to initiate Nbs1/γ-H2AX focus formation and mutations at sites of class switching

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