Mechanisms promoting translocations in editing and switching peripheral B cells

Wang, Jing H.; Gostissa, Monica; Yan, Catherine T.; Goff, Peter H.; Hickernell, Thomas R.; Hansen, Erica; Difilippantonio, Simone; Wesemann, Duane R.; Zarrin, Ali A.; Rajewsky, Klaus; Nussenzweig, André; Alt, Frederick W.

doi:10.1038/nature08159

Cited by 114 publications

(162 citation statements)

References 50 publications

(63 reference statements)

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“…These translocations, like all others, require formation of double-strand breaks on both partner chromosomes. In the case of c-myc/IgH translocation, AID creates the DSBs on both partners, but the DSBs on c-myc are rare and limit the frequency of translocation (26,65). This is consistent with the rather low rate of AIDmediated mutation in c-myc and this gene's propensity for highfidelity repair (24,25).…”

Section: Resultssupporting

confidence: 62%

Role of the translocation partner in protection against AID-dependent chromosomal translocations

Janković

Robbiani

Dorsett

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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Chromosome translocations between Ig (Ig) and non-Ig genes are frequently associated with B-cell lymphomas in humans and mice. The best characterized of these is c-myc/IgH translocation, which is associated with Burkitt's lymphoma. These translocations are caused by activation-induced cytidine deaminase (AID), which produces double-strand DNA breaks in both genes. c-myc/IgH translocations are rare events, in part because ATM, p53, and p19 actively suppress them. To further define the mechanism of protection against the accumulation of cells that bear c-myc/IgH translocation, we assayed B cells from mice that carry mutations in cell-cycle and apoptosis regulator proteins that act downstream of p53. We find that PUMA, Bim, and PKCδ are required for protection against c-myc/ IgH translocation, whereas Bcl-XL and BAFF enhance c-myc/IgH translocation. Whether these effects are general or specific to cmyc/IgH translocation and whether AID produces dsDNA breaks in genes other than c-myc and Ig is not known. To examine these questions, we developed an assay for translocation between IgH and Igβ, both of which are somatically mutated by AID. Igβ/IgH, like c-myc/IgH translocations, are AID-dependent, and AID is responsible for lesions on IgH and the non-IgH translocation partners. However, ATM, p53, and p19 do not protect against Igβ/IgH translocations. Instead, B cells are protected against Igβ/IgH translocations by a BAFF-and PKCδ-dependent pathway. We conclude that AIDinduced double-strand breaks in non-Ig genes other than c-myc lead to their translocation, and that at least two nonoverlapping pathways protect against translocations in primary B cells.M ature B-cell lymphomas are frequently associated with chromosomal translocations between Ig loci and non-Ig genes. The latter include c-myc in Burkitt's lymphoma, bcl-2 in follicular lymphoma, bcl-6 in diffuse large-cell lymphoma, and FGFR in multiple myeloma (1-3). These translocations are believed to be important for malignant transformation because they can deregulate the transcription of oncogenes by placing them under the control of the Ig transcriptional elements.Translocations are thought to be particularly prevalent in B-cell lymphomas because B cells undergo a series of DNA remodeling reactions that involve obligate double-strand breaks (DSBs) in Ig loci. V(D)J recombination is the first of these reactions, and is mediated by the RAG1/2 endonuclease (4, 5). This enzyme produces paired hairpin and blunt DNA ends when it cuts recombination signal sequences during antigen receptor gene assembly in developing B-cell precursors (6, 7). Class switch recombination (CSR) and somatic hypermutation (SHM) remodel Ig genes in mature B cells activated during immune responses. CSR is a DNA recombination reaction that alters the effector function of the antibody by replacing one constant region with another without altering the antigen-binding variable region. In contrast to V(D)J recombination, CSR is not sequence-specific but instead regionspecific, resulting in recombinati...

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Section: Resultssupporting

confidence: 62%

Role of the translocation partner in protection against AID-dependent chromosomal translocations

Janković

Robbiani

Dorsett

et al. 2009

Proc. Natl. Acad. Sci. U.S.A.

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“…The decrease of CSR in XRCC4-deficient cells results from an end-joining defect, because XRCC4-deficient B cells activated for CSR often harbor AID-initiated IgH locus chromosomal breaks (14,28). Moreover, AID-dependent IgH locus breaks often are joined in normal XRCC4-deficient B cells to DSBs on other chromosomes to form translocations (14,28).…”

mentioning

confidence: 99%

Alternative end-joining catalyzes robust IgH locus deletions and translocations in the combined absence of ligase 4 and Ku70

Boboilă

Janković

Yan

et al. 2010

Proc. Natl. Acad. Sci. U.S.A.

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Class switch recombination (CSR) in B lymphocytes is initiated by introduction of multiple DNA double-strand breaks (DSBs) into switch (S) regions that flank immunoglobulin heavy chain ( IgH ) constant region exons. CSR is completed by joining a DSB in the donor Sμ to a DSB in a downstream acceptor S region (e.g., Sγ1) by end-joining. In normal cells, many CSR junctions are mediated by classical nonhomologous end-joining (C-NHEJ), which employs the Ku70/80 complex for DSB recognition and XRCC4/DNA ligase 4 for ligation. Alternative end-joining (A-EJ) mediates CSR, at reduced levels, in the absence of C-NHEJ, even in combined absence of Ku70 and ligase 4, demonstrating an A-EJ pathway totally distinct from C-NHEJ. Multiple DSBs are introduced into Sμ during CSR, with some being rejoined or joined to each other to generate internal switch deletions (ISDs). In addition, S-region DSBs can be joined to other chromosomes to generate translocations, the level of which is increased by absence of a single C-NHEJ component (e.g., XRCC4). We asked whether ISD and S-region translocations occur in the complete absence of C-NHEJ (e.g., in Ku70/ligase 4 double-deficient B cells). We found, unexpectedly, that B-cell activation for CSR generates substantial ISD in both Sμ and Sγ1 and that ISD in both is greatly increased by the absence of C-NHEJ. IgH chromosomal translocations to the c-myc oncogene also are augmented in the combined absence of Ku70 and ligase 4. We discuss the implications of these findings for A-EJ in normal and abnormal DSB repair.

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“…Sixth, Tp53 suppresses the frequency of nonmalignant B cells with AID-initiated Igh/c-myc translocations (Ramiro et al, 2006;Santos et al, 2010). Seventh, Tp53 À/À mice with inactivation of NHEJ in mature B cells succumb to tumors with oncogenic Igh/cmyc translocations arising through CSR errors, or clonal translocations involving aberrant Igk and Igl V(D)J recombination (Wang et al, 2008(Wang et al, , 2009). Finally, Tp53 À/À mice with transgenic AID overexpression develop B cell lymphomas containing clonal miR142/ c-myc or Igh/c-myc translocations formed by 'off-target' AID activity (Robbiani et al, 2009).…”

Section: Introductionmentioning

confidence: 99%

Tp53 deletion in B lineage cells predisposes mice to lymphomas with oncogenic translocations

et al. 2011

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Inactivating Tp53 mutations are frequent genetic lesions in human tumors that harbor genomic instability, including B lineage lymphomas with IG translocations. Antigen receptor genes are assembled and modified in developing lymphocytes by RAG/AID-initiated genomic rearrangements that involve the induction of DNA double strand breaks (DSBs). Although TP53 inhibits the persistence of DSBs and induces apoptosis to protect cells from genomic instability and transformation, the development of spontaneous tumors harboring clonal translocations has not been reported in mice that only lack wild-type Tp53 protein or express Tp53 mutants. Tp53-deficient (Tp53 À/À ) mice succumb to T lineage lymphomas lacking clonal translocations but develop B lymphoid tumors containing immunoglobulin (Ig) translocations upon combined inactivation of DSB repair factors, RAG mutation or AID overexpression; mice expressing apoptosis-defective Tp53 mutants develop B cell lymphomas that have not been characterized for potential genomic instability. As somatic rather than germline inactivating mutations of TP53 are typically associated with human cancers and Tp53 deletion has cellular context dependent effects upon lymphocyte transformation, we generated mice with conditional Tp53 deletion in lineage-committed B lymphocytes to avoid complications associated with defective Tp53 responses during embryogenesis and/or in multilineage potential cells and, thereby, directly evaluate the potential physiological role of Tp53 in suppressing translocations in differentiated cells. These mb1-cre:Tp53 flox/flox mice succumbed to lymphoid tumors containing Ig gene rearrangements and immunophenotypes characteristic of B cells from various developmental stages. Most mb1-cre: Tp53 flox/flox tumors harbored clonal translocations, including Igh/c-myc or other oncogenic translocations generated by the aberrant repair of RAG/AID-generated DSBs.Our data indicate that Tp53 serves critical functions in B lineage lymphocytes to prevent transformation caused by translocations in cell populations experiencing physiological levels of RAG/AID-initiated DSB intermediates, and provide evidence that the somatic TP53 mutations found in diffuse large B-cell lymphoma and Burkitt's lymphoma may contribute to the development of these human malignancies.

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Mechanisms promoting translocations in editing and switching peripheral B cells

Cited by 114 publications

References 50 publications

Role of the translocation partner in protection against AID-dependent chromosomal translocations

Role of the translocation partner in protection against AID-dependent chromosomal translocations

Alternative end-joining catalyzes robust IgH locus deletions and translocations in the combined absence of ligase 4 and Ku70

Tp53 deletion in B lineage cells predisposes mice to lymphomas with oncogenic translocations

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