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

Dynamic look at DNA unwinding by a replicative helicase.

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W. M. Keck Structural Biology Laboratory, Howard Hughes Medical Institute, and Cold Spring Harbor Laboratory, Cold Spring Harbor, NY 11724.


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.


ATPase; molecular motors

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