Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures
Abstract Unique among viruses, some giant viruses utilize histones to organize their genomes into nucleosomes. Melbournevirus encodes a distinct H2B-H2A histone doublet variant in addition to the canonical H4-H3 and H2B-H2A doublets. This viral histone variant has a truncated H2B portion and its ami...
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Nature Portfolio
2025-07-01
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| Series: | Nature Communications |
| Online Access: | https://doi.org/10.1038/s41467-025-62031-2 |
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| author | Alejandro Villalta Hugo Bisio Chelsea M. Toner Chantal Abergel Karolin Luger |
| author_facet | Alejandro Villalta Hugo Bisio Chelsea M. Toner Chantal Abergel Karolin Luger |
| author_sort | Alejandro Villalta |
| collection | DOAJ |
| description | Abstract Unique among viruses, some giant viruses utilize histones to organize their genomes into nucleosomes. Melbournevirus encodes a distinct H2B-H2A histone doublet variant in addition to the canonical H4-H3 and H2B-H2A doublets. This viral histone variant has a truncated H2B portion and its amino acid sequence deviates from that of the main viral H2B-H2A throughout the entire coding region. It is less abundant than the main H2B-H2A doublet, is likely essential for melbournevirus fitness, and is conserved in all Marseilleviridae. The cryo-EM structure of a nucleosome-like particle reconstituted with this H2B-H2A variant and viral H4-H3 reveals that only 90 base pairs of DNA are stably bound, significantly less than in eukaryotic nucleosomes and viral nucleosomes made with the main fused viral histone doublets. The reduced ability to bind DNA can be attributed to structural differences between variant and main H2B-H2A. Variant melbournevirus nucleosomes are less stable, possibly aiding rapid genome unpacking to initiate gene expression. Our results highlight the remarkable propensity of giant viruses to appropriate the utility of histones for their specialized purposes. |
| format | Article |
| id | doaj-art-5cf48656a14845aa984f3655cbe2c431 |
| institution | DOAJ |
| issn | 2041-1723 |
| language | English |
| publishDate | 2025-07-01 |
| publisher | Nature Portfolio |
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| series | Nature Communications |
| spelling | doaj-art-5cf48656a14845aa984f3655cbe2c4312025-08-20T03:05:14ZengNature PortfolioNature Communications2041-17232025-07-0116111010.1038/s41467-025-62031-2Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structuresAlejandro Villalta0Hugo Bisio1Chelsea M. Toner2Chantal Abergel3Karolin Luger4Department of Biochemistry, University of Colorado BoulderAix–Marseille University, Centre National de la Recherche Scientifique, Information Génomique & Structurale, Unité Mixte de Recherche 7256 (Institut de Microbiologie de la Méditerranée, FR3479, IM2B)Department of Biochemistry, University of Colorado BoulderAix–Marseille University, Centre National de la Recherche Scientifique, Information Génomique & Structurale, Unité Mixte de Recherche 7256 (Institut de Microbiologie de la Méditerranée, FR3479, IM2B)Department of Biochemistry, University of Colorado BoulderAbstract Unique among viruses, some giant viruses utilize histones to organize their genomes into nucleosomes. Melbournevirus encodes a distinct H2B-H2A histone doublet variant in addition to the canonical H4-H3 and H2B-H2A doublets. This viral histone variant has a truncated H2B portion and its amino acid sequence deviates from that of the main viral H2B-H2A throughout the entire coding region. It is less abundant than the main H2B-H2A doublet, is likely essential for melbournevirus fitness, and is conserved in all Marseilleviridae. The cryo-EM structure of a nucleosome-like particle reconstituted with this H2B-H2A variant and viral H4-H3 reveals that only 90 base pairs of DNA are stably bound, significantly less than in eukaryotic nucleosomes and viral nucleosomes made with the main fused viral histone doublets. The reduced ability to bind DNA can be attributed to structural differences between variant and main H2B-H2A. Variant melbournevirus nucleosomes are less stable, possibly aiding rapid genome unpacking to initiate gene expression. Our results highlight the remarkable propensity of giant viruses to appropriate the utility of histones for their specialized purposes.https://doi.org/10.1038/s41467-025-62031-2 |
| spellingShingle | Alejandro Villalta Hugo Bisio Chelsea M. Toner Chantal Abergel Karolin Luger Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures Nature Communications |
| title | Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures |
| title_full | Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures |
| title_fullStr | Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures |
| title_full_unstemmed | Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures |
| title_short | Melbournevirus encodes a shorter H2B-H2A doublet histone variant that forms structurally distinct nucleosome structures |
| title_sort | melbournevirus encodes a shorter h2b h2a doublet histone variant that forms structurally distinct nucleosome structures |
| url | https://doi.org/10.1038/s41467-025-62031-2 |
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