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Proc Natl Acad Sci U S A. 2017 Jan 24;114(4):E466-E475. doi: 10.1073/pnas.1615439114. Epub 2017 Jan 9.

Shuttling along DNA and directed processing of D-loops by RecQ helicase support quality control of homologous recombination.

Author information

1
Department of Biochemistry, Eötvös Loránd University-Hungarian Academy of Sciences "Momentum" Motor Enzymology Research Group, Eötvös Loránd University, H-1117 Budapest, Hungary.
2
Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892.
3
Department of Genetics, Eötvös Loránd University, H-1117 Budapest, Hungary.
4
Laboratory of Single Molecule Biophysics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892; mihaly.kovacs@ttk.elte.hu neumankc@mail.nih.gov.
5
Department of Biochemistry, Eötvös Loránd University-Hungarian Academy of Sciences "Momentum" Motor Enzymology Research Group, Eötvös Loránd University, H-1117 Budapest, Hungary; mihaly.kovacs@ttk.elte.hu neumankc@mail.nih.gov.

Abstract

Cells must continuously repair inevitable DNA damage while avoiding the deleterious consequences of imprecise repair. Distinction between legitimate and illegitimate repair processes is thought to be achieved in part through differential recognition and processing of specific noncanonical DNA structures, although the mechanistic basis of discrimination remains poorly defined. Here, we show that Escherichia coli RecQ, a central DNA recombination and repair enzyme, exhibits differential processing of DNA substrates based on their geometry and structure. Through single-molecule and ensemble biophysical experiments, we elucidate how the conserved domain architecture of RecQ supports geometry-dependent shuttling and directed processing of recombination-intermediate [displacement loop (D-loop)] substrates. Our study shows that these activities together suppress illegitimate recombination in vivo, whereas unregulated duplex unwinding is detrimental for recombination precision. Based on these results, we propose a mechanism through which RecQ helicases achieve recombination precision and efficiency.

KEYWORDS:

DNA unwinding; RecQ; helicase; magnetic tweezers; single molecule

PMID:
28069956
PMCID:
PMC5278487
DOI:
10.1073/pnas.1615439114
[Indexed for MEDLINE]
Free PMC Article

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