53BP1 regulates DNA resection and the choice between classical and alternative end joining during class switch recombination

2010 ◽  
Vol 189 (2) ◽  
pp. i3-i3
Author(s):  
Anne Bothmer ◽  
Davide F. Robbiani ◽  
Niklas Feldhahn ◽  
Anna Gazumyan ◽  
Andre Nussenzweig ◽  
...  
Keyword(s):  
Class Switch Recombination ◽  
End Joining ◽  
Class Switch ◽  
Alternative End Joining ◽  
Dna Resection

scholarly journals Alternative end-joining catalyzes class switch recombination in the absence of both Ku70 and DNA ligase 4

2010 ◽  
Vol 207 (2) ◽  
pp. 417-427 ◽  
Author(s):  
Cristian Boboila ◽  
Catherine Yan ◽  
Duane R. Wesemann ◽  
Mila Jankovic ◽  
Jing H. Wang ◽  
...  
Keyword(s):  
B Cells ◽  
Class Switch Recombination ◽  
Strand Break ◽  
Nonhomologous End Joining ◽  
Dna Ligase ◽  
End Joining ◽  
Dsb Repair ◽  
Class Switch ◽  
Dna Double Strand Break ◽  
Alternative End Joining

The classical nonhomologous end-joining (C-NHEJ) DNA double-strand break (DSB) repair pathway employs the Ku70/80 complex (Ku) for DSB recognition and the XRCC4/DNA ligase 4 (Lig4) complex for ligation. During IgH class switch recombination (CSR) in B lymphocytes, switch (S) region DSBs are joined by C-NHEJ to form junctions either with short microhomologies (MHs; “MH-mediated” joins) or no homologies (“direct” joins). In the absence of XRCC4 or Lig4, substantial CSR occurs via “alternative” end-joining (A-EJ) that generates largely MH-mediated joins. Because upstream C-NHEJ components remain in XRCC4- or Lig4-deficient B cells, residual CSR might be catalyzed by C-NHEJ using a different ligase. To address this, we have assayed for CSR in B cells deficient for Ku70, Ku80, or both Ku70 and Lig4. Ku70- or Ku80-deficient B cells have reduced, but still substantial, CSR. Strikingly, B cells deficient for both Ku plus Lig4 undergo CSR similarly to Ku-deficient B cells, firmly demonstrating that an A-EJ pathway distinct from C-NHEJ can catalyze CSR end-joining. Ku-deficient or Ku- plus Lig4-deficient B cells are also biased toward MH-mediated CSR joins; but, in contrast to XRCC4- or Lig4-deficient B cells, generate substantial numbers of direct CSR joins. Our findings suggest that more than one form of A-EJ can function in CSR.

scholarly journals Alternative end-joining catalyzes class switch recombination in the absence of both Ku70 and DNA ligase 4

2013 ◽  
Vol 210 (3) ◽  
pp. 641-641 ◽  
Author(s):  
Cristian Boboila ◽  
Catherine Yan ◽  
Duane R. Wesemann ◽  
Mila Jankovic ◽  
Jing H. Wang ◽  
...  
Keyword(s):  
Class Switch Recombination ◽  
Dna Ligase ◽  
End Joining ◽  
Class Switch ◽  
Alternative End Joining

scholarly journals Alternative end-joining catalyzes class switch recombination in the absence of both Ku70 and DNA ligase 4

2010 ◽  
Vol 188 (4) ◽  
pp. i7-i7
Author(s):  
Cristian Boboila ◽  
Catherine Yan ◽  
Duane R. Wesemann ◽  
Mila Jankovic ◽  
Jing H. Wang ◽  
...  
Keyword(s):  
Class Switch Recombination ◽  
Dna Ligase ◽  
End Joining ◽  
Class Switch ◽  
Alternative End Joining

scholarly journals Multiple DSB Resection Activities Redundantly Promote Alternative End Joining-Mediated Class Switch Recombination

2021 ◽  
Vol 9 ◽  
Author(s):  
Xikui Sun ◽  
Jingning Bai ◽  
Jiejie Xu ◽  
Xiaoli Xi ◽  
Mingyu Gu ◽  
...  
Keyword(s):  
High Throughput Sequencing ◽  
Class Switch Recombination ◽  
Class Switching ◽  
End Joining ◽  
Independent Manner ◽  
Class Switch ◽  
Alternative End Joining ◽  
A Cell ◽  
Non Homologous End Joining ◽  
Antibody Class

Alternative end joining (A-EJ) catalyzes substantial level of antibody class switch recombination (CSR) in B cells deficient for classical non-homologous end joining, featuring increased switch (S) region DSB resection and junctional microhomology (MH). While resection has been suggested to initiate A-EJ in model DSB repair systems using engineered endonucleases, the contribution of resection factors to A-EJ-mediated CSR remains unclear. In this study, we systematically dissected the requirement for individual DSB resection factors in A-EJ-mediated class switching with a cell-based assay system and high-throughput sequencing. We show that while CtIP and Mre11 both are mildly required for CSR in WT cells, they play more critical roles in mediating A-EJ CSR, which depend on the exonuclease activity of Mre11. While DNA2 and the helicase/HRDC domain of BLM are required for A-EJ by mediating long S region DSB resection, in contrast, Exo1’s resection-related function does not play any obvious roles for class switching in either c-NHEJ or A-EJ cells, or mediated in an AID-independent manner by joining of Cas9 breaks. Furthermore, ATM and its kinase activity functions at least in part independent of CtIP/Mre11 to mediate A-EJ switching in Lig4-deficient cells. In stark contrast to Lig4 deficiency, 53BP1-deficient cells do not depend on ATM/Mre11/CtIP for residual joining. We discuss the roles for each resection factor in A-EJ-mediated CSR and suggest that the extent of requirements for resection is context dependent.

scholarly journals Elucidation of the enigmatic IgD class-switch recombination via germline deletion of the IgH 3′ regulatory region

2014 ◽  
Vol 211 (5) ◽  
pp. 975-985 ◽  
Author(s):  
Pauline Rouaud ◽  
Alexis Saintamand ◽  
Faten Saad ◽  
Claire Carrion ◽  
Sandrine Lecardeur ◽  
...  
Keyword(s):  
Somatic Hypermutation ◽  
Regulatory Region ◽  
Class Switch Recombination ◽  
End Joining ◽  
Class Switch ◽  
Classical Class ◽  
Mesenteric Lymph ◽  
Alternative End Joining ◽  
Activation Induced Deaminase ◽  
Deficient Mice

Classical class-switch recombination (cCSR) substitutes the Cμ gene with Cγ, Cε, or Cα, thereby generating IgG, IgE, or IgA classes, respectively. This activation-induced deaminase (AID)–driven process is controlled by the IgH 3′ regulatory region (3′RR). Regulation of rare IgD CSR events has been enigmatic. We show that μδCSR occurs in mouse mesenteric lymph node (MLN) B cells and is AID-dependent. AID attacks differ from those in cCSR because they are not accompanied by extensive somatic hypermutation (SHM) of targeted regions and because repaired junctions exhibit features of the alternative end-joining (A-EJ) pathway. In contrast to cCSR and SHM, μδCSR is 3′RR-independent, as its absence affects neither breakpoint locations in Sμ- and Sδ-like (σδ) nor mutation patterns at Sμ-σδ junctions. Although mutations occur in the immediate proximity of the μδ junctions, SHM is absent distal to the junctions within both Sμ and rearranged VDJ regions. In conclusion, μδCSR is active in MLNs, occurs independently of 3′RR-driven assembly, and is even dramatically increased in 3′RR-deficient mice, further showing that its regulation differs from cCSR.

scholarly journals HMCES Functions in the Alternative End-Joining Pathway of the DNA DSB Repair during Class Switch Recombination in B Cells

2020 ◽  
Vol 77 (5) ◽  
pp. 1154 ◽  
Author(s):  
Vipul Shukla ◽  
Levon Halabelian ◽  
Sanjana Balagere ◽  
Daniela Samaniego-Castruita ◽  
Douglas E. Feldman ◽  
...  
Keyword(s):  
B Cells ◽  
Class Switch Recombination ◽  
End Joining ◽  
Dsb Repair ◽  
Class Switch ◽  
Alternative End Joining

scholarly journals CtIP-mediated DNA resection is dispensable for IgH class switch recombination by alternative end-joining

2020 ◽  
Vol 117 (41) ◽  
pp. 25700-25711
Author(s):  
Xiaobin S. Wang ◽  
Junfei Zhao ◽  
Foon Wu-Baer ◽  
Zhengping Shao ◽  
Brian J. Lee ◽  
...  
Keyword(s):  
B Cells ◽  
High Throughput Sequencing ◽  
Class Switch Recombination ◽  
End Joining ◽  
Atm Kinase ◽  
Class Switch ◽  
Switch Regions ◽  
Alternative End Joining ◽  
Dna End Resection ◽  
End Resection

To generate antibodies with different effector functions, B cells undergo Immunoglobulin Heavy Chain (IgH) class switch recombination (CSR). The ligation step of CSR is usually mediated by the classical nonhomologous end-joining (cNHEJ) pathway. In cNHEJ-deficient cells, a remarkable ∼25% of CSR can be achieved by the alternative end-joining (Alt-EJ) pathway that preferentially uses microhomology (MH) at the junctions. While A-EJ-mediated repair of endonuclease-generated breaks requires DNA end resection, we show that CtIP-mediated DNA end resection is dispensable for A-EJ-mediated CSR using cNHEJ-deficient B cells. High-throughput sequencing analyses revealed that loss of ATM/ATR phosphorylation of CtIP at T855 or ATM kinase inhibition suppresses resection without altering the MH pattern of the A-EJ-mediated switch junctions. Moreover, we found that ATM kinase promotes Alt-EJ-mediated CSR by suppressing interchromosomal translocations independent of end resection. Finally, temporal analyses reveal that MHs are enriched in early internal deletions even in cNHEJ-proficient B cells. Thus, we propose that repetitive IgH switch regions represent favored substrates for MH-mediated end-joining contributing to the robustness and resection independence of A-EJ-mediated CSR.

scholarly journals HMCES Functions in the Alternative End-Joining Pathway of the DNA DSB Repair during Class Switch Recombination in B Cells

2020 ◽  
Vol 77 (2) ◽  
pp. 384-394.e4 ◽  
Author(s):  
Vipul Shukla ◽  
Levon Halabelian ◽  
Sanjana Balagere ◽  
Daniela Samaniego-Castruita ◽  
Douglas E. Feldman ◽  
...  
Keyword(s):  
B Cells ◽  
Class Switch Recombination ◽  
End Joining ◽  
Dsb Repair ◽  
Class Switch ◽  
Alternative End Joining
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