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Updated: Jun 25, 2025
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Assembly of Nucleosomal Arrays from Recombinant Core Histones and Nucleosome Positioning DNA
Published on: September 10, 2013
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Self-assembling viral histones are evolutionary intermediates between archaeal and eukaryotic nucleosomes
Nicholas A T Irwin1,2,3, Thomas A Richards4
1Merton College, University of Oxford, Oxford, UK. nicholas.irwin@gmi.oeaw.ac.at.
Nature Microbiology
|May 28, 2024
Summary
Viral histone repeats, found in viruses, may represent an evolutionary link between archaeal and eukaryotic histones. These viral proteins self-assemble into nucleosome-like structures, offering insights into chromatin evolution.
Area of Science:
- Molecular Biology
- Evolutionary Biology
- Virology
Background:
- Nucleosomes, fundamental to eukaryotic chromatin, are DNA-protein complexes of histone proteins.
- The evolutionary origin of nucleosomes from archaeal histone homologues is not well understood.
- Viral histone repeats, with multiple histone paralogues in one protein, present a potential intermediate in nucleosome evolution.
Purpose of the Study:
- To investigate the diversity and evolutionary significance of histones encoded by Nucleocytoviricota viruses.
- To explore the potential role of viral histone repeats as intermediates in the evolution of eukaryotic nucleosomes.
Main Methods:
- Bioinformatic analysis of 258 histones from 168 viral metagenomes.
- Phylogenetic analysis to determine evolutionary relationships.
- Functional assays in *Escherichia coli* to assess nucleosome formation and DNA condensation.
Main Results:
- Identified viral histones with diverse domain configurations (singlets to quadruplets).
- Viral histone repeats phylogenetically positioned between Archaea and eukaryotes.
- Demonstrated intermediate functions, including self-assembly into eukaryotic-like nucleosomes and archaeal-like oligomers, impacting DNA condensation.
Conclusions:
- Viral histone repeats support the hypothesis of originating in stem-eukaryotes.
- Nucleosome evolution likely involved histone repeat intermediates.
- Viral histones provide a model for understanding early chromatin organization.
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