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Open AccessJournal ArticleDOI

Fork sensing and strand switching control antagonistic activities of RecQ helicases

TLDR
This work investigates the DNA unwinding of RecQ helicases from Arabidopsis thaliana, AtRECQ2 and AtRECZ3 at the single-molecule level using magnetic tweezers and provides a simple explanation for how different biological activities can be achieved by rather similar members of the RecQ family.
Abstract
RecQ helicases have essential roles in maintaining genome stability during replication and in controlling double-strand break repair by homologous recombination. Little is known about how the different RecQ helicases found in higher eukaryotes achieve their specialized and partially opposing functions. Here, we investigate the DNA unwinding of RecQ helicases from Arabidopsis thaliana, AtRECQ2 and AtRECQ3 at the single-molecule level using magnetic tweezers. Although AtRECQ2 predominantly unwinds forked DNA substrates in a highly repetitive fashion, AtRECQ3 prefers to rewind, that is, to close preopened DNA forks. For both enzymes, this process is controlled by frequent strand switches and active sensing of the unwinding fork. The relative extent of the strand switches towards unwinding or towards rewinding determines the predominant direction of the enzyme. Our results provide a simple explanation for how different biological activities can be achieved by rather similar members of the RecQ family.

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Camera-based three-dimensional real-time particle tracking at kHz rates and Ångström accuracy

TL;DR: This work demonstrates that camera-based imaging can provide a similar performance for all three dimensions of particle tracking with Ångström accuracy as laser detection through photodiodes, and provides a simple and robust way for high-resolution tweezers experiments using multiple particles at a time.
Journal ArticleDOI

Mechanistic insight into the interaction of BLM helicase with intra-strand G-quadruplex structures.

TL;DR: It is shown that the activity of BLM is substrate dependent, and highly regulated by a short ssDNA segment that separates the G4 motif from dsDNA, and a model is presented that proposes a unique role for G4 structures in modulating theActivity of DNA processing enzymes.
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Human DNA2 possesses a cryptic DNA unwinding activity that functionally integrates with BLM or WRN helicases

TL;DR: It is shown that the helicase of hDNA2 functionally integrates with BLM or WRN helicases to promote dsDNA degradation by forming a heterodimeric molecular machine, which collectively suggests that the h DNA2 motor promotes the enzyme's capacity to degrade ds DNA in conjunction with BLMor WRN and thus promote the repair of broken DNA.
Journal ArticleDOI

Dynamic look at DNA unwinding by a replicative helicase

TL;DR: The findings reveal that E1 employs a strand exclusion mechanism to unwind DNA with the N-terminal side leading at the replication fork, and DNA unwinding by E1 is modulated by the origin-recognition domain, suggesting a previously unsuspected role for this domain in regulating helicase activity.
Journal ArticleDOI

Extending the Range for Force Calibration in Magnetic Tweezers

TL;DR: The force calibration based on the long pendulum geometry will facilitate high-resolution magnetic-tweezers experiments that rely on short molecules and large forces, as well as highly parallelized measurements that use low frame rates.
References
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Journal ArticleDOI

Probing the structural basis of RecQ helicase function.

TL;DR: This review illustrates the recent progress made in the definition of the structural determinants that control the different enzymatic activities of RecQ helicases and speculates on the possible mechanisms that RecQ proteins might use to promote their multiple functions.
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Structure and function of the regulatory HRDC domain from human Bloom syndrome protein

TL;DR: It is suggested that the HRDC domain of Bloom syndrome protein may be adapted for a unique function among RecQ helicases—that of bridging protein and DNA interactions.
Journal ArticleDOI

A variant of the breast cancer type 2 susceptibility protein (BRC) repeat is essential for the RECQL5 helicase to interact with RAD51 recombinase for genome stabilization.

TL;DR: A BRC repeat variant is identified in the RECQL5 helicase, which possesses anti-recombinase activity in vitro and suppresses HR and promotes cellular resistance to camptothecin-induced replication stress in vivo.
Journal ArticleDOI

Dynamics of initiation, termination and reinitiation of DNA translocation by the motor protein EcoR124I.

TL;DR: It is found that the methyltransferase core unit of the enzyme loads the motor subunits onto adjacent DNA by allowing them to bind and initiate translocation, allowing dynamic control of the restriction process by the availability of motors.
Journal ArticleDOI

Efficient preparation of internally modified single-molecule constructs using nicking enzymes.

TL;DR: It is shown how long stretches of DNA can be modified using nicking enzymes to produce complex DNA constructs, and offers promise for a wide range of applications, in particular single-molecule experiments, where frequently multiple internal DNA modifications are required.
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