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Science. 2017 Jul 28;357(6349). pii: eaag0025. doi: 10.1126/science.aag0025.

ChromEMT: Visualizing 3D chromatin structure and compaction in interphase and mitotic cells.

Author information

1
Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA.
2
National Center for Microscopy and Imaging Research, Center for Research in Biological Systems, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
3
Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA.
4
Molecular and Cell Biology Laboratory, Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA. oshea@salk.edu.

Abstract

The chromatin structure of DNA determines genome compaction and activity in the nucleus. On the basis of in vitro structures and electron microscopy (EM) studies, the hierarchical model is that 11-nanometer DNA-nucleosome polymers fold into 30- and subsequently into 120- and 300- to 700-nanometer fibers and mitotic chromosomes. To visualize chromatin in situ, we identified a fluorescent dye that stains DNA with an osmiophilic polymer and selectively enhances its contrast in EM. Using ChromEMT (ChromEM tomography), we reveal the ultrastructure and three-dimensional (3D) organization of individual chromatin polymers, megabase domains, and mitotic chromosomes. We show that chromatin is a disordered 5- to 24-nanometer-diameter curvilinear chain that is packed together at different 3D concentration distributions in interphase and mitosis. Chromatin chains have many different particle arrangements and bend at various lengths to achieve structural compaction and high packing densities.

Comment in

PMID:
28751582
PMCID:
PMC5646685
DOI:
10.1126/science.aag0025
[Indexed for MEDLINE]
Free PMC Article

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