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Bending Unwinds DNA.


ABSTRACT: In biology, DNA is often tightly bent to small radii. Solely based on the groove asymmetry, a 30-year-old theoretical paper predicted that such bending should unwind DNA, but this effect has not been directly experimentally quantified so far. We developed a ligation-based assay with nicked DNA circles of variable length, thereby decoupling the twist-dependent ligation efficiency from the large bending strain which dominates conventional circularization assays. We demonstrate that tightly bent DNA indeed unwinds to over 11 base pairs/turn, exactly as predicted. Our discovery requires reassessing the molecular mechanisms and energetics of all processes where DNA is tightly bent or relaxed again, including DNA packaging, gene regulation and expression.

SUBMITTER: Chandrasekhar S 

PROVIDER: S-EPMC10888926 | biostudies-literature | 2024 Feb

REPOSITORIES: biostudies-literature

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Bending DNA increases its helical repeat.

Chandrasekhar Soumya S   Swope Thomas P TP   Fadaei Fatemeh F   Hollis Daniel R DR   Bricker Rachel R   Houser Draven D   Portman John J JJ   Schmidt Thorsten L TL  

bioRxiv : the preprint server for biology 20241127


In all biological systems, DNA is under high mechanical stress from bending and twisting. For example, DNA is tightly bent in nucleosome complexes, virus capsids, bacterial chromosomes, or complexes with transcription factors that regulate gene expression. A structurally and mechanically accurate model of DNA is therefore necessary to understand some of the most fundamental molecular mechanisms in biology including DNA packaging, replication, transcription and gene regulation. An iconic feature  ...[more]

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