Dataset Information

Probing Nucleosome Stability with a DNA Origami Nanocaliper.

ABSTRACT: The organization of eukaryotic DNA into nucleosomes and chromatin undergoes dynamic structural changes to regulate genome processing, including transcription and DNA repair. Critical chromatin rearrangements occur over a wide range of distances, including the mesoscopic length scale of tens of nanometers. However, there is a lack of methodologies that probe changes over this mesoscopic length scale within chromatin. We have designed, constructed, and implemented a DNA-based nanocaliper that probes this mesoscopic length scale. We developed an approach of integrating nucleosomes into our nanocaliper at two attachment points with over 50% efficiency. Here, we focused on attaching the two DNA ends of the nucleosome to the ends of the two nanocaliper arms, so the hinge angle is a readout of the nucleosome end-to-end distance. We demonstrate that nucleosomes integrated with 6, 26, and 51 bp linker DNA are partially unwrapped by the nanocaliper by an amount consistent with previously observed structural transitions. In contrast, the nucleosomes integrated with the longer 75 bp linker DNA remain fully wrapped. We found that the nanocaliper angle is a sensitive measure of nucleosome disassembly and can read out transcription factor (TF) binding to its target site within the nucleosome. Interestingly, the nanocaliper not only detects TF binding but also significantly increases the probability of TF occupancy at its site by partially unwrapping the nucleosome. These studies demonstrate the feasibility of using DNA nanotechnology to both detect and manipulate nucleosome structure, which provides a foundation of future mesoscale studies of nucleosome and chromatin structural dynamics.

SUBMITTER: Le JV

PROVIDER: S-EPMC5460529 | biostudies-literature | 2016 Jul

REPOSITORIES: biostudies-literature

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Probing Nucleosome Stability with a DNA Origami Nanocaliper.

Le Jenny V JV Luo Yi Y Darcy Michael A MA Lucas Christopher R CR Goodwin Michelle F MF Poirier Michael G MG Castro Carlos E CE

ACS nano 20160706 7

The organization of eukaryotic DNA into nucleosomes and chromatin undergoes dynamic structural changes to regulate genome processing, including transcription and DNA repair. Critical chromatin rearrangements occur over a wide range of distances, including the mesoscopic length scale of tens of nanometers. However, there is a lack of methodologies that probe changes over this mesoscopic length scale within chromatin. We have designed, constructed, and implemented a DNA-based nanocaliper that prob ...[more]

PMID: 27362329

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Project description:Methylation of DNA at CpG dinucleotides represents one of the most important epigenetic mechanisms involved in the control of gene expression in vertebrate cells. In this report, we conducted high-throughput nucleosome reconstitution experiments on 572 KB of human DNA and 668 KB of mouse DNA that was unmethylated or methylated in order to investigate the effects of this epigenetic modification on the positioning and stability of nucleosomes. The DNA loci from both species contained the genes that encode the serum albumin family, the MYC protein, and the tumor suppressor p53. The results demonstrated that a small subset of nucleosomes positioned by nucleotide sequence was sensitive to methylation where the modification increased the affinity of these sequences for the histone octamer. The features that distinguished these nucleosomes from the bulk of the methylation-insensitive nucleosomes were an increase in the frequency of CpG dinucleotides and a unique rotational orientation of CpGs such that their minor grooves tended to face toward the histones in the nucleosome rather than away. We propose that these features serve to enhance the affinity of methylated DNA for the histone octamer and that this effect could be involved in gene regulatory mechanisms such as silencing. These methylation-sensitive nucleosomes were preferentially associated with exons as compared to introns while unmethylated CpG islands near transcription start sites became enriched in nucleosomes upon methylation. The results of this study suggest that the effects of DNA methylation on nucleosome stability in vitro can recapitulate what has been observed in the cell and provide a direct link between DNA methylation and the structure and function of chromatin. For the human data, there were 3 unmethylated nucleosome replicates, 2 methylated nucleosome replicates, an unmethylated MNase control, and an unmethylated sonicated control. For the mouse data, there were 2 unmethylated nucleosome replicates, 2 methylated nucleosome replicates, an unmethylated MNase control, a methylated MNase control, and an unmethylated sonicated control.

Dataset Information

Probing Nucleosome Stability with a DNA Origami Nanocaliper.

Publications

Probing Nucleosome Stability with a DNA Origami Nanocaliper.

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