期刊
MOLECULAR BIOLOGY AND EVOLUTION
卷 39, 期 2, 页码 -出版社
OXFORD UNIV PRESS
DOI: 10.1093/molbev/msac019
关键词
histone variants; gene duplication; pseudogenes; positive selection; oogenesis; spermatogenesis
资金
- Fondation pour la Recherche Medicale [FRM: AJE201912009932]
- National Institute of General Medical Sciences at the National Institutes of Health [R35 GM139429, R01 GM074108]
- Howard Hughes Medical Institute
Histones and their posttranslational modifications play diverse chromatin functions in eukaryotes. This study reveals the presence of five H2B variants widely present in mammalian genomes, with two new variants identified. These variants are broadly retained in mammals and expressed in germline cells. The findings suggest that H2B variants likely have important roles in mammalian germline cells through unconventional chromatin packaging or nonchromatin functions.
Histones and their posttranslational modifications facilitate diverse chromatin functions in eukaryotes. Core histones (H2A, H2B, H3, and H4) package genomes after DNA replication. In contrast, variant histones promote specialized chromatin functions, including DNA repair, genome stability, and epigenetic inheritance. Previous studies have identified only a few H2B variants in animals; their roles and evolutionary origins remain largely unknown. Here, using phylogenomic analyses, we reveal the presence of five H2B variants broadly present in mammalian genomes. Three of these variants have been previously described: H2B.1, H2B.L (also called subH2B), and H2B.W. In addition, we identify and describe two new variants: H2B.K and H2B.N. Four of these variants originated in mammals, whereas H2B.K arose prior to the last common ancestor of bony vertebrates. We find that though H2B variants are subject to high gene turnover, most are broadly retained in mammals, including humans. Despite an overall signature of purifying selection, H2B variants evolve more rapidly than core H2B with considerable divergence in sequence and length. All five H2B variants are expressed in the germline. H2B.K and H2B.N are predominantly expressed in oocytes, an atypical expression site for mammalian histone variants. Our findings suggest that H2B variants likely encode potentially redundant but vital functions via unusual chromatin packaging or nonchromatin functions in mammalian germline cells. Our discovery of novel histone variants highlights the advantages of comprehensive phylogenomic analyses and provides unique opportunities to study how innovations in chromatin function evolve.
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