Overlapping functions between XLF repair protein and 53BP1 DNA damage response factor in end joining and lymphocyte development.
Proc Natl Acad Sci U S A
; 109(10): 3903-8, 2012 Mar 06.
Article
em En
| MEDLINE
| ID: mdl-22355127
ABSTRACT
Nonhomologous end joining (NHEJ), a major pathway of DNA double-strand break (DSB) repair, is required during lymphocyte development to resolve the programmed DSBs generated during Variable, Diverse, and Joining [V(D)J] recombination. XRCC4-like factor (XLF) (also called Cernunnos or NHEJ1) is a unique component of the NHEJ pathway. Although germ-line mutations of other NHEJ factors abrogate lymphocyte development and lead to severe combined immunodeficiency (SCID), XLF mutations cause a progressive lymphocytopenia that is generally less severe than SCID. Accordingly, XLF-deficient murine lymphocytes show no measurable defects in V(D)J recombination. We reported earlier that ATM kinase and its substrate histone H2AX are both essential for V(D)J recombination in XLF-deficient lymphocytes, despite moderate role in V(D)J recombination in WT cells. p53-binding protein 1 (53BP1) is another substrate of ATM. 53BP1 deficiency led to small reduction of peripheral lymphocyte number by compromising both synapse and end-joining at modest level during V(D)J recombination. Here, we report that 53BP1/XLF double deficiency blocks lymphocyte development at early progenitor stages, owing to severe defects in end joining during chromosomal V(D)J recombination. The unrepaired DNA ends are rapidly degraded in 53BP1(-/-)XLF(-/-) cells, as reported for H2AX(-/-)XLF(-/-) cells, revealing an end protection role for 53BP1 reminiscent of H2AX. In contrast to the early embryonic lethality of H2AX(-/-)XLF(-/-) mice, 53BP1(-/-)XLF(-/-) mice are born alive and develop thymic lymphomas with translocations involving the T-cell receptor loci. Together, our findings identify a unique function for 53BP1 in end-joining and tumor suppression.
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Base de dados:
MEDLINE
Assunto principal:
Proteínas Cromossômicas não Histona
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Linfócitos
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Regulação da Expressão Gênica
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Proteínas Serina-Treonina Quinases
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Proteínas de Ciclo Celular
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Proteínas Supressoras de Tumor
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Proteínas de Ligação a DNA
Limite:
Animals
Idioma:
En
Ano de publicação:
2012
Tipo de documento:
Article