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A giant virus genome is densely packaged by stable nucleosomes within virions.

Authors :: Bryson TD
De Ioannes P
Valencia-Sánchez MI
Henikoff JG
Talbert PB
Lee R
La Scola B
Armache KJ
Henikoff S
Source :: Molecular cell [Mol Cell] 2022 Dec 01; Vol. 82 (23), pp. 4458-4470.e5. Date of Electronic Publication: 2022 Nov 11.
Publication Year :: 2022
Abstract: The two doublet histones of Marseillevirus are distantly related to the four eukaryotic core histones and wrap 121 base pairs of DNA to form remarkably similar nucleosomes. By permeabilizing Marseillevirus virions and performing genome-wide nuclease digestion, chemical cleavage, and mass spectrometry assays, we find that the higher-order organization of Marseillevirus chromatin fundamentally differs from that of eukaryotes. Marseillevirus nucleosomes fully protect DNA within virions as closely abutted 121-bp DNA-wrapped cores without linker DNA or phasing along genes. Likewise, we observed that nucleosomes reconstituted onto multi-copy tandem repeats of a nucleosome-positioning sequence are tightly packed. Dense promiscuous packing of fully wrapped nucleosomes rather than "beads on a string" with genic punctuation represents a distinct mode of DNA packaging by histones. We suggest that doublet histones have evolved for viral genome protection and may resemble an early stage of histone differentiation leading to the eukaryotic octameric nucleosome.<br />Competing Interests: Declaration of interests The authors declare no competing interests.<br /> (Copyright © 2022 The Author(s). Published by Elsevier Inc. All rights reserved.)