Mechanistic insight into the assembly of the HerA-NurA helicase-nuclease DNA end resection complex

Zainab Ahdash, Andy M. Lau, Robert Thomas Byrne, Katja Lammens, Alexandra Stüetzer, Henning Urlaub, Paula J. Booth, Eamonn Reading, Karl Peter Hopfner, Argyris Politis

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The HerA-NurA helicase-nuclease complex cooperates with Mre11 and Rad50 to coordinate the repair of double-stranded DNA breaks. Little is known, however, about the assembly mechanism and activation of the HerA-NurA. By combining hybrid mass spectrometry with cryo-EM, computational and biochemical data, we investigate the oligomeric formation of HerA and detail the mechanism of nucleotide binding to the HerA-NurA complex from thermophilic archaea. We reveal that ATP-free HerA and HerA-DNA complexes predominantly exist in solution as a heptamer and act as a DNA loading intermediate. The binding of either NurA or ATP stabilizes the hexameric HerA, indicating that HerA-NurA is activated by substrates and complex assembly. To examine the role of ATP in DNA translocation and processing, we investigated how nucleotides interact with the HerA-NurA. We show that while the hexameric HerA binds six nucleotides in an 'all-or-none' fashion, HerA-NurA harbors a highly coordinated pairwise binding mechanism and enables the translocation and processing of double-stranded DNA. Using molecular dynamics simulations, we reveal novel inter-residue interactions between the external ATP and the internal DNA binding sites. Overall, here we propose a stepwise assembly mechanism detailing the synergistic activation of HerA-NurA by ATP, which allows efficient processing of double-stranded DNA.

Original languageEnglish
Pages (from-to)12025-12038
Number of pages14
JournalNucleic Acids Research
Issue number20
Early online date9 Oct 2017
Publication statusPublished - 16 Nov 2017


  • Journal Article


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