9QV6

Asgard HHoB hypernucleosome in the closed state

Summary for 9QV6

• Entry DOI: 10.2210/pdb9qv6/pdb
• Related: 9QV5 9QV6 9QV7
• EMDB information: 53386 53387 53388 53389 53390
• Descriptor: Archaeal histone A, DNA (180-MER) (3 entities in total)
• Functional Keywords: archaea, asgard, chromatin, histone, dna, nucleosome, dna binding protein
• Biological source: Candidatus Heimdallarchaeota archaeon LC_3; More
• Total number of polymer chains: 14
• Total formula weight: 204707.57

Authors

Ranawat, H.M.,Dodonova, S.O. (deposition date: 2025-04-11, release date: 2025-10-29, Last modification date: 2025-12-03)

Primary citation

Ranawat, H.M.,Cajili, M.K.,Lopez-Barbosa, N.,Quail, T.,Dame, R.T.,Dodonova, S.O.
Cryo-EM reveals open and closed Asgard chromatin assemblies.
Mol.Cell, 85:4152-, 2025

PubMed Abstract: Asgards are the closest archaeal relatives of eukaryotes, representing an important step in chromatin evolution. However, their chromatin organization has remained enigmatic until now. In this study, we present the first structures of Asgard chromatin assemblies formed by the Hodarchaeal histone HHoB. Our high-resolution cryo-electron microscopy (cryo-EM) structures reveal that this Asgard histone assembles into compact "closed" and into extended "open" hypernucleosomes. Thus, the closed hypernucleosome conformation is conserved across archaeal lineages, while the open conformation resembles a eukaryotic H3-H4 octasome and likely represents an Asgard-specific innovation. Moreover, we show that Mg²⁺ ions influence Asgard chromatin conformation, suggesting a regulatory role. Overall, our study provides the first structure-based model of Asgard chromatin organization, expanding our understanding of chromatin architecture in an evolutionary context.

PubMed: 41161312
DOI: 10.1016/j.molcel.2025.10.001

Experimental method

ELECTRON MICROSCOPY (2.6 Å)