Loading…
AFM studies in diverse ionic environments of nucleosomes reconstituted on the 601 positioning sequence
Atomic force microscopy (AFM) was used to study mononucleosomes reconstituted from a DNA duplex of 353 bp containing the strong 601 octamer positioning sequence, together with recombinant human core histone octamers. Three parameters were measured: 1) the length of DNA wrapped around the core histon...
Saved in:
Published in: | Biochimie 2016-02, Vol.121, p.5-12 |
---|---|
Main Authors: | , , , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
Tags: |
Add Tag
No Tags, Be the first to tag this record!
|
Summary: | Atomic force microscopy (AFM) was used to study mononucleosomes reconstituted from a DNA duplex of 353 bp containing the strong 601 octamer positioning sequence, together with recombinant human core histone octamers. Three parameters were measured: 1) the length of DNA wrapped around the core histones; 2) the number of superhelical turns, calculated from the total angle through which the DNA is bent, and 3) the volume of the DNA-histone core. This approach allowed us to define in detail the structural diversity of nucleosomes caused by disassembly of the octasome to form subnucleosomal structures containing hexasomes, tetrasomes and disomes. At low ionic strength (TE buffer) and in the presence of physiological concentrations of monovalent cations, the majority of the particles were subnucleosomal, but physiological concentrations of bivalent cations resulted in about half of the nucleosomes being canonical octasomes in which the exiting DNA duplexes cross orthogonally. The dominance of this last species explains why bivalent but not monovalent cations can induce the initial step towards compaction and convergence of neighboring nucleosomes in nucleosomal arrays to form the chromatin fiber in the absence of linker histone. The observed nucleosome structural diversity may reflect the functional plasticity of nucleosomes under physiological conditions.
[Display omitted]
•AFM image analysis defines 4 species of nucleosome/sub-nucleosome.•They contain octameric, hexameric, tetrameric and dimeric core histones.•Divalent cations stabilize nucleosomes containing octameric histone (octasomes).•The linker DNAs of octasomes cross orthogonally.•The ‘crossed linker’ conformation may promote formation of higher order structure. |
---|---|
ISSN: | 0300-9084 1638-6183 |
DOI: | 10.1016/j.biochi.2015.11.010 |