Stepwise 5' DNA end-specific resection of DNA breaks by the Mre11-Rad50-Xrs2 and Sae2 nuclease ensemble.
Proc Natl Acad Sci U S A
; 116(12): 5505-5513, 2019 03 19.
Article
em En
| MEDLINE
| ID: mdl-30819891
ABSTRACT
To repair DNA double-strand breaks by homologous recombination, the 5'-terminated DNA strands must first be resected to produce 3' overhangs. Mre11 from Saccharomyces cerevisiae is a 3' â 5' exonuclease that is responsible for 5' end degradation in vivo. Using plasmid-length DNA substrates and purified recombinant proteins, we show that the combined exonuclease and endonuclease activities of recombinant MRX-Sae2 preferentially degrade the 5'-terminated DNA strand, which extends beyond the vicinity of the DNA end. Mechanistically, Rad50 restricts the Mre11 exonuclease in an ATP binding-dependent manner, preventing 3' end degradation. Phosphorylated Sae2, along with stimulating the MRX endonuclease as shown previously, also overcomes this inhibition to promote the 3' â 5' exonuclease of MRX, which requires ATP hydrolysis by Rad50. Our results support a model in which MRX-Sae2 catalyzes 5'-DNA end degradation by stepwise endonucleolytic DNA incisions, followed by exonucleolytic 3' â 5' degradation of the individual DNA fragments. This model explains how both exonuclease and endonuclease activities of Mre11 functionally integrate within the MRX-Sae2 ensemble to resect 5'-terminated DNA.
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01-internacional
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MEDLINE
Assunto principal:
DNA
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Proteínas de Saccharomyces cerevisiae
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Proteínas de Ligação a DNA
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Endodesoxirribonucleases
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Endonucleases
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Exodesoxirribonucleases
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Quebras de DNA de Cadeia Dupla
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Reparo do DNA por Junção de Extremidades
Idioma:
En
Revista:
Proc Natl Acad Sci U S A
Ano de publicação:
2019
Tipo de documento:
Article
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