Ring-shaped replicative helicase encircles double-stranded DNA during unwinding

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Title
Ring-shaped replicative helicase encircles double-stranded DNA during unwinding
Author(s)
Sihwa Joo; Bong Hyun Chung; M Lee; Tai Hwan Ha
Bibliographic Citation
Nucleic Acids Research, vol. 47, no. 21, pp. 11344-11354
Publication Year
2019
Abstract
Ring-shaped replicative helicases are hexameric and play a key role in cellular DNA replication. Despite their importance, our understanding of the unwinding mechanism of replicative helicases is far from perfect. Bovine papillomavirus E1 is one of the best-known model systems for replicative helicases. E1 is a multifunctional initiator that senses and melts the viral origin and unwinds DNA. Here, we study the unwinding mechanism of E1 at the single-molecule level using magnetic tweezers. The result reveals that E1 as a single hexamer is a poorly processive helicase with a low unwinding rate. Tension on the DNA strands impedes unwinding, indicating that the helicase interacts strongly with both DNA strands at the junction. While investigating the interaction at a high force (26-30 pN), we discovered that E1 encircles dsDNA. By comparing with the E1 construct without a DNA binding domain, we propose two possible encircling modes of E1 during active unwinding.
ISSN
0305-1048
Publisher
Oxford Univ Press
DOI
http://dx.doi.org/10.1093/nar/gkz893
Type
Article
Appears in Collections:
Division of Bio Technology Innovation > Core Research Facility & Analysis Center > 1. Journal Articles
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