摘要The compaction of genomic DNA into nucleosomes with the help of histones has long been considered a fundamental feature exclusive to eukaryotic cells.However,it was recently shown that archaea and bacteria also encode histones.A complex picture has emerged with more recent discoveries of eukaryotic-like histones within one phylum of double-stranded DNA(dsDNA)viruses.Nevertheless,the extent to which other dsDNA viruses encode histones remains largely unexplored.Here,we conducted a metagenomic survey of viral histones that were further clustered based on sequence and predicted structural similarities.We identified over 1500 viral histones and histone-fold proteins,including previ-ously undescribed proteins found in the viral class Caudoviricetes.Structural predictions and in vitro assays demon-strated that histone triplets(where three histone folds are fused)and singlets co-occurring in the same viral genome are capable of forming nucleosome-like particles.Beyond nucleosomal histone functions,our analysis revealed six types of structurally and functionally diverse viral histone-fold proteins,some of which do not have known structural or functional homologs.Altogether,our findings reveal a previously unrecognized diversity of viral histones in dsDNA viruses,expanding the known repertoire,structural diversity,and functional versatility of viral histones beyond nucle-ocytoplasmic large DNA viruses.