Histone-mediated chromatin organization in prokaryotes and viruses

Histones are fundamental chromatin-organizing proteins in eukaryotes and archaea, where they assemble into (hyper)nucleosomes that wrap DNA. Recent studies have expanded the known repertoire of histones, identifying new variants in both prokaryotes and large DNA viruses. In prokaryotes, histones exhibit a range of DNA-binding modes, including wrapping, bending, and bridging, rather than exclusively forming nucleosomes. Notably, large DNA viruses encode histone paralogs that structurally resemble eukaryotic core histones and assemble into nucleosome-like complexes. This review summarizes recent discoveries on canonical archaeal nucleosomal histones and newly identified histones in archaea, bacteria, and viruses, highlighting their structural and functional diversity in genome organization.