Table of Contents Author Guidelines Submit a Manuscript
Journal of Nucleic Acids
Volume 2012, Article ID 140601, 14 pages
Review Article

Unwinding and Rewinding: Double Faces of Helicase?

Department of Biochemistry, University of Saskatchewan, Health Sciences Building, Saskatoon, SK, Canada S7N 5E5

Received 12 April 2012; Accepted 28 May 2012

Academic Editor: Grigory Dianov

Copyright © 2012 Yuliang Wu. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Helicases are enzymes that use ATP-driven motor force to unwind double-stranded DNA or RNA. Recently, increasing evidence demonstrates that some helicases also possess rewinding activity—in other words, they can anneal two complementary single-stranded nucleic acids. All five members of the human RecQ helicase family, helicase PIF1, mitochondrial helicase TWINKLE, and helicase/nuclease Dna2 have been shown to possess strand-annealing activity. Moreover, two recently identified helicases—HARP and AH2 have only ATP-dependent rewinding activity. These findings not only enhance our understanding of helicase enzymes but also establish the presence of a new type of protein: annealing helicases. This paper discusses what is known about these helicases, focusing on their biochemical activity to zip and unzip double-stranded DNA and/or RNA, their possible regulation mechanisms, and biological functions.