Dynamic look at DNA unwinding by a replicative helicase

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 111; no. 9; pp. E827 - E835
• Main Authors: Lee, Seung-Jae, Syed, Salman, Enemark, Eric J., Schuck, Stephen, Stenlund, Arne, Ha, Taekjip, Joshua-Tor, Leemor
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 04.03.2014; National Acad Sciences
• Series: PNAS Plus
• Subjects: Base Sequence; Biological Sciences; Deoxyribonucleic acid; DNA; DNA - chemistry; DNA - genetics; DNA - metabolism; DNA Helicases - genetics; DNA Helicases - metabolism; DNA replication; DNA-binding domains; DNA-Binding Proteins - chemistry; DNA-Binding Proteins - genetics; DNA-Binding Proteins - metabolism; Fluorescence Resonance Energy Transfer; Human papillomavirus; mechanistic models; Models, Biological; Models, Molecular; Molecular Sequence Data; Molecules; Mutagenesis, Site-Directed; Nucleic Acid Conformation; Papillomavirus; PNAS Plus; Spectrometry, Fluorescence; Viral Proteins - chemistry; Viral Proteins - genetics; Viral Proteins - metabolism; molecular motors; ATPase
• ISSN: 0027-8424; 1091-6490; 1091-6490
• DOI: 10.1073/pnas.1322254111

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.