Inhibition of E. coli RecQ Helicase Activity by Structurally Distinct DNA Lesions: Structure—Function Relationships

Ana H. Sales, Vincent Zheng, Maya A. Kenawy, Mark Kakembo, Lu Zhang, Vladimir Shafirovich, Suse Broyde, Nicholas E. Geacintov

Research output: Contribution to journalArticlepeer-review


DNA helicase unwinding activity can be inhibited by small molecules and by covalently bound DNA lesions. Little is known about the relationships between the structural features of DNA lesions and their impact on unwinding rates and processivities. Employing E.coli RecQ helicase as a model system, and various conformationally defined DNA lesions, the unwinding rate constants kobs = kU + kD, and processivities P = (kU/(kU + kD) were determined (kU, unwinding rate constant; kD, helicase-DNA dissociation rate constant). The highest kobs values were observed in the case of intercalated benzo[a]pyrene (BP)-derived adenine adducts, while kobs values of guanine adducts with minor groove or base-displaced intercalated adduct conformations were ~10–20 times smaller. Full unwinding was observed in each case with the processivity P = 1.0 (100% unwinding). The kobs values of the non-bulky lesions T(6−4)T, CPD cyclobutane thymine dimers, and a guanine oxidation product, spiroiminodihydantoin (Sp), are up to 20 times greater than some of the bulky adduct values; their unwinding efficiencies are strongly inhibited with processivities P = 0.11 (CPD), 0.062 (T(6−4)T), and 0.63 (Sp). These latter observations can be accounted for by correlated decreases in unwinding rate constants and enhancements in the helicase DNA complex dissociation rate constants.

Original languageEnglish (US)
Article number15654
JournalInternational journal of molecular sciences
Issue number24
StatePublished - Dec 2022


  • CPD and (6-4) thymine dimers
  • RecQ helicase
  • benzo[a]pyene diol epoxide-DNA adducts
  • processivities
  • spiroiminodihydantoin
  • unwinding

ASJC Scopus subject areas

  • Catalysis
  • Molecular Biology
  • Spectroscopy
  • Computer Science Applications
  • Physical and Theoretical Chemistry
  • Organic Chemistry
  • Inorganic Chemistry


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