Published in

National Academy of Sciences, Proceedings of the National Academy of Sciences, 23(119), 2022

DOI: 10.1073/pnas.2116462119

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The convergence of head-on DNA unwinding forks induces helicase oligomerization and activity transition

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

Significance Bloom syndrome helicase (BLM) is a multifunctional helicase that primarily catalyzes the separation of two single strands of DNA. Here, using a single-molecule optical tweezers approach combined with confocal microscopy, we monitored both the enzymatic activity and oligomeric status of BLM at the same time. Strikingly, a head-on collision of BLM-medicated DNA unwinding forks was found to effectively switch their oligomeric state and activity. Specifically, BLMs, upon collision, immediately fuse across the fork junctions and covert their activities from dsDNA unwinding to ssDNA translocation and protein displacement. These findings explain how BLM plays multiple functional roles in homologous recombination (HR). The single-molecule approach used here provides a reference model for investigating the relationship between protein oligomeric state and function.