Dynamic look at DNA unwinding by a replicative helicase

Proc Natl Acad Sci U S A. 2014 Mar 4;111(9):E827-35. doi: 10.1073/pnas.1322254111. Epub 2014 Feb 18.


A prerequisite for DNA replication is the unwinding of duplex DNA catalyzed by a replicative hexameric helicase. Despite a growing body of research, key elements of helicase mechanism remain under substantial debate. In particular, the number of DNA strands encircled by the helicase ring during unwinding and the ring orientation at the replication fork completely contrast in contemporary mechanistic models. Here we use single-molecule and ensemble assays to address these questions for the papillomavirus E1 helicase. We find that E1 unwinds DNA with a strand-exclusion mechanism, with the N-terminal side of the helicase ring facing the replication fork. We show that E1 generates strikingly heterogeneous unwinding patterns stemming from varying degrees of repetitive movements, which is modulated by the DNA-binding domain. Together, our studies reveal previously unrecognized dynamic facets of replicative helicase unwinding mechanisms.

Keywords: ATPase; molecular motors.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Base Sequence
  • DNA / chemistry
  • DNA / genetics
  • DNA / metabolism*
  • DNA Helicases / genetics
  • DNA Helicases / metabolism*
  • DNA-Binding Proteins / chemistry
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism*
  • Fluorescence Resonance Energy Transfer
  • Models, Biological
  • Models, Molecular*
  • Molecular Sequence Data
  • Mutagenesis, Site-Directed
  • Nucleic Acid Conformation*
  • Spectrometry, Fluorescence
  • Viral Proteins / chemistry
  • Viral Proteins / genetics
  • Viral Proteins / metabolism*


  • DNA-Binding Proteins
  • E1 protein, Bovine papillomavirus
  • Viral Proteins
  • DNA
  • DNA Helicases