Activation of p38 MAP kinase by DNA double-strand breaks in V(D)J recombination induces a G2/M cell cycle checkpoint

Ataxia telangiectasia mutated (ATM) is a central kinase that activates an extensive network of responses to cellular stress via a signaling role. ATM is activated by DNA double strand breaks (DSBs) and by oxidative stress, subsequently phosphorylating a plethora of target proteins. In the last several decades, newly developed molecular biological techniques have uncovered multiple roles of ATM in response to DNA damage—e.g., DSB repair, cell cycle checkpoint arrest, apoptosis, and transcription arrest. Combinational dysfunction of these stress responses impairs the accuracy of repair, consequently leading to dramatic sensitivity to ionizing radiation (IR) in ataxia telangiectasia (A-T) cells. In this review, we summarize the roles of ATM that focus on DSB repair.

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RAG-mediated DNA double-strand breaks activate a cell type–specific checkpoint to inhibit pre–B cell receptor signals

Journal of Experimental Medicine ◽

10.1084/jem.20151048 ◽

2016 ◽

Vol 213 (2) ◽

pp. 209-223 ◽

Cited By ~ 22

Author(s):

Jeffrey J. Bednarski ◽

Ruchi Pandey ◽

Emily Schulte ◽

Lynn S. White ◽

Bo-Ruei Chen ◽

...

Keyword(s):

Cell Cycle ◽

B Cells ◽

B Cell ◽

Cell Receptor ◽

B Cell Receptor ◽

Cell Cycle Checkpoint ◽

Double Strand Breaks ◽

Chain Gene ◽

Dna Double Strand Breaks ◽

Strand Breaks

DNA double-strand breaks (DSBs) activate a canonical DNA damage response, including highly conserved cell cycle checkpoint pathways that prevent cells with DSBs from progressing through the cell cycle. In developing B cells, pre–B cell receptor (pre–BCR) signals initiate immunoglobulin light (Igl) chain gene assembly, leading to RAG-mediated DNA DSBs. The pre–BCR also promotes cell cycle entry, which could cause aberrant DSB repair and genome instability in pre–B cells. Here, we show that RAG DSBs inhibit pre–BCR signals through the ATM- and NF-κB2–dependent induction of SPIC, a hematopoietic-specific transcriptional repressor. SPIC inhibits expression of the SYK tyrosine kinase and BLNK adaptor, resulting in suppression of pre–BCR signaling. This regulatory circuit prevents the pre–BCR from inducing additional Igl chain gene rearrangements and driving pre–B cells with RAG DSBs into cycle. We propose that pre–B cells toggle between pre–BCR signals and a RAG DSB-dependent checkpoint to maintain genome stability while iteratively assembling Igl chain genes.

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53BP1 is required for class switch recombination

The Journal of Cell Biology ◽

10.1083/jcb.200403021 ◽

2004 ◽

Vol 165 (4) ◽

pp. 459-464 ◽

Cited By ~ 233

Author(s):

Irene M. Ward ◽

Bernardo Reina-San-Martin ◽

Alexandru Olaru ◽

Kay Minn ◽

Koji Tamada ◽

...

Keyword(s):

Class Switch Recombination ◽

Cell Cycle Checkpoint ◽

Double Strand Breaks ◽

Nonhomologous End Joining ◽

Checkpoint Control ◽

Dna Double Strand Breaks ◽

End Joining ◽

Strand Breaks ◽

Class Switch ◽

Cycle Checkpoint

53BP1 participates early in the DNA damage response and is involved in cell cycle checkpoint control. Moreover, the phenotype of mice and cells deficient in 53BP1 suggests a defect in DNA repair (Ward et al., 2003b). Therefore, we asked whether or not 53BP1 would be required for the efficient repair of DNA double strand breaks. Our data indicate that homologous recombination by gene conversion does not depend on 53BP1. Moreover, 53BP1-deficient mice support normal V(D)J recombination, indicating that 53BP1 is not required for “classic” nonhomologous end joining. However, class switch recombination is severely impaired in the absence of 53BP1, suggesting that 53BP1 facilitates DNA end joining in a way that is not required or redundant for the efficient closing of RAG-induced strand breaks. These findings are similar to those observed in mice or cells deficient in the tumor suppressors ATM and H2AX, further suggesting that the functions of ATM, H2AX, and 53BP1 are closely linked.

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Artemis Links ATM to G2/M Checkpoint Recovery via Regulation of Cdk1-Cyclin B

Molecular and Cellular Biology ◽

10.1128/mcb.02072-06 ◽

2007 ◽

Vol 27 (7) ◽

pp. 2625-2635 ◽

Cited By ~ 38

Author(s):

Liyi Geng ◽

Xiaoshan Zhang ◽

Shu Zheng ◽

Randy J. Legerski

Keyword(s):

Cell Cycle ◽

Dna Damage ◽

Cell Cycle Checkpoint ◽

Nonhomologous End Joining ◽

Cyclin B ◽

End Joining ◽

M Cell ◽

Strand Breaks ◽

Checkpoint Recovery ◽

Cycle Checkpoint

ABSTRACT Artemis is a phospho-protein that has been shown to have roles in V(D)J recombination, nonhomologous end-joining of double-strand breaks, and regulation of the DNA damage-induced G2/M cell cycle checkpoint. Here, we have identified four sites in Artemis that are phosphorylated in response to ionizing radiation (IR) and show that ATM is the major kinase responsible for these modifications. Two of the sites, S534 and S538, show rapid phosphorylation and dephosphorylation, and the other two sites, S516 and S645, exhibit rapid and prolonged phosphorylation. Mutation of both of these latter two residues results in defective recovery from the G2/M cell cycle checkpoint. This defective recovery is due to promotion by mutant Artemis of an enhanced interaction between unphosphorylated cyclin B and Cdk1, which in turn promotes inhibitory phosphorylation of Cdk1 by the Wee1 kinase. In addition, we show that mutant Artemis prevents Cdk1-cyclin B activation by causing its retention in the centrosome and inhibition of its nuclear import during prophase. These findings show that ATM regulates G2/M checkpoint recovery through inhibitory phosphorylations of Artemis that occur soon after DNA damage, thus setting a molecular switch that, hours later upon completion of DNA repair, allows activation of the Cdk1-cyclin B complex. These findings thus establish a novel function of Artemis as a regulator of the cell cycle in response to DNA damage.

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Repair pathway choice for double-strand breaks

Essays in Biochemistry ◽

10.1042/ebc20200007 ◽

2020 ◽

Vol 64 (5) ◽

pp. 765-777 ◽

Cited By ~ 2

Author(s):

Yixi Xu ◽

Dongyi Xu

Keyword(s):

Cell Cycle ◽

Double Strand Breaks ◽

Homologous Region ◽

Gene Repair ◽

Repair Pathway ◽

Dna Double Strand Breaks ◽

Environmental Radiation ◽

Strand Breaks ◽

Dna End Resection ◽

End Resection

Abstract Deoxyribonucleic acid (DNA) is at a constant risk of damage from endogenous substances, environmental radiation, and chemical stressors. DNA double-strand breaks (DSBs) pose a significant threat to genomic integrity and cell survival. There are two major pathways for DSB repair: nonhomologous end-joining (NHEJ) and homologous recombination (HR). The extent of DNA end resection, which determines the length of the 3′ single-stranded DNA (ssDNA) overhang, is the primary factor that determines whether repair is carried out via NHEJ or HR. NHEJ, which does not require a 3′ ssDNA tail, occurs throughout the cell cycle. 53BP1 and the cofactors PTIP or RIF1-shieldin protect the broken DNA end, inhibit long-range end resection and thus promote NHEJ. In contrast, HR mainly occurs during the S/G2 phase and requires DNA end processing to create a 3′ tail that can invade a homologous region, ensuring faithful gene repair. BRCA1 and the cofactors CtIP, EXO1, BLM/DNA2, and the MRE11–RAD50–NBS1 (MRN) complex promote DNA end resection and thus HR. DNA resection is influenced by the cell cycle, the chromatin environment, and the complexity of the DNA end break. Herein, we summarize the key factors involved in repair pathway selection for DSBs and discuss recent related publications.

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