scholarly journals The Ataxia Telangiectasia mutated kinase controls Igκ allelic exclusion by inhibiting secondary Vκ-to-Jκ rearrangements

2013 ◽  
Vol 210 (2) ◽  
pp. 233-239 ◽  
Author(s):  
Natalie C. Steinel ◽  
Baeck-Seung Lee ◽  
Anthony T. Tubbs ◽  
Jeffrey J. Bednarski ◽  
Emily Schulte ◽  
...  
Keyword(s):  
Ataxia Telangiectasia ◽  
Feedback Inhibition ◽  
Allelic Exclusion ◽  
Dna Double Strand Breaks ◽  
Ataxia Telangiectasia Mutated ◽  
Strand Breaks ◽  
Histone H2ax ◽  
Dependent Protein ◽  
Time Required ◽  
Histone H2ax Phosphorylation

Allelic exclusion is enforced through the ability of antigen receptor chains expressed from one allele to signal feedback inhibition of V-to-(D)J recombination on the other allele. To achieve allelic exclusion by such means, only one allele can initiate V-to-(D)J recombination within the time required to signal feedback inhibition. DNA double-strand breaks (DSBs) induced by the RAG endonuclease during V(D)J recombination activate the Ataxia Telangiectasia mutated (ATM) and DNA-dependent protein kinase (DNA-PK) kinases. We demonstrate that ATM enforces Igκ allelic exclusion, and that RAG DSBs induced during Igκ recombination in primary pre–B cells signal through ATM, but not DNA-PK, to suppress initiation of additional Igκ rearrangements. ATM promotes high-density histone H2AX phosphorylation to create binding sites for MDC1, which functions with H2AX to amplify a subset of ATM-dependent signals. However, neither H2AX nor MDC1 is required for ATM to enforce Igκ allelic exclusion and suppress Igκ rearrangements. Upon activation in response to RAG Igκ cleavage, ATM signals down-regulation of Gadd45α with concomitant repression of the Gadd45α targets Rag1 and Rag2. Our data indicate that ATM kinases activated by RAG DSBs during Igκ recombination transduce transient H2AX/MDC1-independent signals that suppress initiation of further Igκ rearrangements to control Igκ allelic exclusion.

scholarly journals DNA-Dependent Protein Kinase Catalytic Subunit: The Sensor for DNA Double-Strand Breaks Structurally and Functionally Related to Ataxia Telangiectasia Mutated

Genes ◽  
2021 ◽  
Vol 12 (8) ◽  
pp. 1143
Author(s):  
Yoshihisa Matsumoto ◽  
Anie Day D. C. Asa ◽  
Chaity Modak ◽  
Mikio Shimada
Keyword(s):  
Protein Kinase ◽  
Ataxia Telangiectasia ◽  
Catalytic Subunit ◽  
Nonhomologous End Joining ◽  
Dna Double Strand Breaks ◽  
Ataxia Telangiectasia Mutated ◽  
End Joining ◽  
Dependent Protein Kinase ◽  
Strand Breaks ◽  
Dependent Protein

The DNA-dependent protein kinase (DNA-PK) is composed of a DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and Ku70/Ku80 heterodimer. DNA-PK is thought to act as the “sensor” for DNA double-stranded breaks (DSB), which are considered the most deleterious type of DNA damage. In particular, DNA-PKcs and Ku are shown to be essential for DSB repair through nonhomologous end joining (NHEJ). The phenotypes of animals and human individuals with defective DNA-PKcs or Ku functions indicate their essential roles in these developments, especially in neuronal and immune systems. DNA-PKcs are structurally related to Ataxia–telangiectasia mutated (ATM), which is also implicated in the cellular responses to DSBs. DNA-PKcs and ATM constitute the phosphatidylinositol 3-kinase-like kinases (PIKKs) family with several other molecules. Here, we review the accumulated knowledge on the functions of DNA-PKcs, mainly based on the phenotypes of DNA-PKcs-deficient cells in animals and human individuals, and also discuss its relationship with ATM in the maintenance of genomic stability.

scholarly journals DNA structure-specific priming of ATR activation by DNA-PKcs

2013 ◽  
Vol 202 (3) ◽  
pp. 421-429 ◽  
Author(s):  
Sophie Vidal-Eychenié ◽  
Chantal Décaillet ◽  
Jihane Basbous ◽  
Angelos Constantinou
Keyword(s):  
Dna Damage ◽  
Ataxia Telangiectasia ◽  
Protein A ◽  
Dna Structure ◽  
Specific Response ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Synergistic Activation ◽  
Dependent Protein ◽  
Specific Priming

Three phosphatidylinositol-3-kinase–related protein kinases implement cellular responses to DNA damage. DNA-dependent protein kinase catalytic subunit (DNA-PKcs) and ataxia-telangiectasia mutated respond primarily to DNA double-strand breaks (DSBs). Ataxia-telangiectasia and RAD3-related (ATR) signals the accumulation of replication protein A (RPA)–covered single-stranded DNA (ssDNA), which is caused by replication obstacles. Stalled replication intermediates can further degenerate and yield replication-associated DSBs. In this paper, we show that the juxtaposition of a double-stranded DNA end and a short ssDNA gap triggered robust activation of endogenous ATR and Chk1 in human cell-free extracts. This DNA damage signal depended on DNA-PKcs and ATR, which congregated onto gapped linear duplex DNA. DNA-PKcs primed ATR/Chk1 activation through DNA structure-specific phosphorylation of RPA32 and TopBP1. The synergistic activation of DNA-PKcs and ATR suggests that the two kinases combine to mount a prompt and specific response to replication-born DSBs.

scholarly journals ATM’s Role in the Repair of DNA Double-Strand Breaks

Genes ◽  
2021 ◽  
Vol 12 (9) ◽  
pp. 1370
Author(s):  
Atsushi Shibata ◽  
Penny A. Jeggo
Keyword(s):  
Stress Responses ◽  
Ataxia Telangiectasia ◽  
Cell Cycle Checkpoint ◽  
Double Strand Breaks ◽  
Multiple Roles ◽  
Dna Double Strand Breaks ◽  
Ataxia Telangiectasia Mutated ◽  
Dsb Repair ◽  
Strand Breaks ◽  
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.

scholarly journals An Oligomerized 53BP1 Tudor Domain Suffices for Recognition of DNA Double-Strand Breaks

2008 ◽  
Vol 29 (4) ◽  
pp. 1050-1058 ◽  
Author(s):  
Omar Zgheib ◽  
Kristopher Pataky ◽  
Juergen Brugger ◽  
Thanos D. Halazonetis
Keyword(s):  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Checkpoint Proteins ◽  
Strand Breaks ◽  
Histone H2ax ◽  
Dna Dsbs ◽  
Tudor Domain ◽  
Histone Core ◽  
Histone H2ax Phosphorylation ◽  
Oligomerization Domain

ABSTRACT 53BP1, the vertebrate ortholog of the budding yeast Rad9 and fission yeast Crb2/Rhp9 checkpoint proteins, is recruited rapidly to sites of DNA double-strand breaks (DSBs). A tandem tudor domain in human 53BP1 that recognizes methylated residues in the histone core is necessary, but not sufficient, for efficient recruitment. By analysis of deletion mutants, we identify here additional elements in 53BP1 that facilitate recognition of DNA DSBs. The first element corresponds to an independently folding oligomerization domain. Replacement of this domain with heterologous tetramerization domains preserves the ability of 53BP1 to recognize DNA DSBs. A second element is only about 15 amino acids long and appears to be a C-terminal extension of the tudor domain, rather than an independently functioning domain. Recruitment of 53BP1 to sites of DNA DSBs is facilitated by histone H2AX phosphorylation and ubiquitination. However, none of the 53BP1 domains/elements important for recruitment are known to bind phosphopeptides or ubiquitin, suggesting that histone phosphorylation and ubiquitination regulate 53BP1 recruitment to sites of DNA DSBs indirectly.

ATM deficiency disrupts Tcra locus integrity and the maturation of CD4+CD8+ thymocytes

Blood ◽  
2006 ◽  
Vol 109 (5) ◽  
pp. 1887-1896 ◽  
Author(s):  
Irina R. Matei ◽  
Rebecca A. Gladdy ◽  
Lauryl M. J. Nutter ◽  
Angelo Canty ◽  
Cynthia J. Guidos ◽  
...  
Keyword(s):  
T Cell ◽  
Ataxia Telangiectasia ◽  
Cell Receptor ◽  
Double Strand Breaks ◽  
Dna Double Strand Breaks ◽  
Ataxia Telangiectasia Mutated ◽  
Apoptotic Pathway ◽  
Strand Breaks ◽  
Striking Contrast

Abstract Mutations in ATM (ataxia-telangiectasia mutated) cause ataxia-telangiectasia (AT), a disease characterized by neurodegeneration, sterility, immunodeficiency, and T-cell leukemia. Defective ATM-mediated DNA damage responses underlie many aspects of the AT syndrome, but the basis for the immune deficiency has not been defined. ATM associates with DNA double-strand breaks (DSBs), and some evidence suggests that ATM may regulate V(D)J recombination. However, it remains unclear how ATM loss compromises lymphocyte development in vivo. Here, we show that T-cell receptor β (TCRβ)–dependent proliferation and production of TCRβlow CD4+CD8+ (DP) thymocytes occurred normally in Atm−/− mice. In striking contrast, the postmitotic maturation of TCRβlow DP precursors into TCRβint DP cells and TCRβhi mature thymocytes was profoundly impaired. Furthermore, Atm−/− thymocytes expressed abnormally low amounts of TCRα mRNA and protein. These defects were not attributable to the induction of a BCL-2–sensitive apoptotic pathway. Rather, they were associated with frequent biallelic loss of distal Va gene segments in DP thymocytes, revealing that ATM maintains Tcra locus integrity as it undergoes V(D)J recombination. Collectively, our data demonstrate that ATM loss increases the frequency of aberrant Tcra deletion events, which compromise DP thymocyte maturation and likely promote the generation of oncogenic TCR translocations.

scholarly journals Histone H2AX stabilizes broken DNA strands to suppress chromosome breaks and translocations during V(D)J recombination

2009 ◽  
Vol 206 (12) ◽  
pp. 2625-2639 ◽  
Author(s):  
Bu Yin ◽  
Velibor Savic ◽  
Marisa M. Juntilla ◽  
Andrea L. Bredemeyer ◽  
Katherine S. Yang-Iott ◽  
...  
Keyword(s):  
Cellular Proliferation ◽  
Antigen Receptor ◽  
Dna Double Strand Breaks ◽  
Strand Breaks ◽  
Histone H2ax ◽  
Chromosome Breaks ◽  
Receptor Locus ◽  
Dna Strands ◽  
Dependent Protein ◽  
Antigen Receptor Loci

The H2AX core histone variant is phosphorylated in chromatin around DNA double strand breaks (DSBs) and functions through unknown mechanisms to suppress antigen receptor locus translocations during V(D)J recombination. Formation of chromosomal coding joins and suppression of translocations involves the ataxia telangiectasia mutated and DNA-dependent protein kinase catalytic subunit serine/threonine kinases, each of which phosphorylates H2AX along cleaved antigen receptor loci. Using Abelson transformed pre–B cell lines, we find that H2AX is not required for coding join formation within chromosomal V(D)J recombination substrates. Yet we show that H2AX is phosphorylated along cleaved Igκ DNA strands and prevents their separation in G1 phase cells and their progression into chromosome breaks and translocations after cellular proliferation. We also show that H2AX prevents chromosome breaks emanating from unrepaired RAG endonuclease-generated TCR-α/δ locus coding ends in primary thymocytes. Our data indicate that histone H2AX suppresses translocations during V(D)J recombination by creating chromatin modifications that stabilize disrupted antigen receptor locus DNA strands to prevent their irreversible dissociation. We propose that such H2AX-dependent mechanisms could function at additional chromosomal locations to facilitate the joining of DNA ends generated by other types of DSBs.

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