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Modulation of Archaeal Hypernucleosome Structure and Stability by Mg2
Ilias Zarguit1, Marc K M Cajili1, Bert van Erp1
1Leiden Institute of Chemistry, Leiden University, Einsteinweg 55, 2333CC Leiden, the Netherlands; Centre for Microbial Cell Biology, Leiden University, Leiden, the Netherlands; Centre for Interdisciplinary Genome Research, Leiden University, Leiden, the Netherlands.
Journal of Molecular Biology
|November 7, 2025
Summary
Archaeal histones form DNA-protein hypernucleosomes, a structure conserved across species. Magnesium ions influence hypernucleosome stability through electrostatic shielding, with effects varying by histone type.
Area of Science:
- Structural biology
- Molecular biology
- Biophysics
Background:
- Histone proteins organize DNA into chromatin in eukaryotes and archaea.
- Archaeal histones form unique 'endless' superhelical complexes called hypernucleosomes.
- The conservation and regulation of archaeal hypernucleosomes remain underexplored.
Purpose of the Study:
- To investigate the conserved nature of hypernucleosome formation in canonical archaeal histones.
- To examine the influence of magnesium ions (Mg2+) on hypernucleosome structure and stability.
- To elucidate the regulatory mechanisms governing archaeal hypernucleosomes.
Main Methods:
- Tethered Particle Motion (TPM) for DNA dynamics.
- Single-molecule force spectroscopy for structural analysis.
- Comparative analysis of histone complexes with DNA.
Main Results:
- T. kodakarensis histones form hypernucleosomes on DNA, confirming conserved formation.
- Mg2+ ions impact hypernucleosome compactness and stability.
- Distinct Mg2+ effects were observed despite high histone sequence and structural similarity.
Conclusions:
- Hypernucleosome formation is a conserved feature of canonical archaeal histones.
- Mg2+ ions play a dual role: general electrostatic shielding and specific histone-dependent modulation.
- A model is proposed for Mg2+ influence on archaeal hypernucleosome dynamics.
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