1. Ring-shaped replicative helicase encircles double-stranded DNA during unwinding
- Author
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Bong Hyun Chung, Mina Lee, Tai Hwan Ha, and Sihwa Joo
- Subjects
DNA Replication ,Models, Molecular ,Magnetic tweezers ,Protein Conformation ,viruses ,DNA, Single-Stranded ,Random hexamer ,Viral Proteins ,03 medical and health sciences ,chemistry.chemical_compound ,0302 clinical medicine ,Protein structure ,Escherichia coli ,Genetics ,Protein Interaction Domains and Motifs ,A-DNA ,030304 developmental biology ,0303 health sciences ,biology ,Nucleic Acid Enzymes ,DNA Helicases ,DNA replication ,Helicase ,DNA ,DNA-Binding Proteins ,chemistry ,biology.protein ,Biophysics ,Nucleic Acid Conformation ,Protein Multimerization ,030217 neurology & neurosurgery ,Binding domain - 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.
- Published
- 2019
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