Bryson_MOLECULAR-CELL-D-22-00555_Figure_S1A
Description
A giant virus genome is densely packaged by stable nucleosomes within virions. The two doublet histones of Marseillevirus are distantly related to the four eukaryotic core histones and wrap 121 basepairs 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 new 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. Marseillevirus nucleosomes are mostly insoluble after MNase treatment. Tapestation gel image of DNA purified from breached Marseillevirus T19 virus particles after NP40 treatment for times as indicated and 5 min MNase digestion.
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Steps to reproduce
1) Loaded 2 µL each DNA sample + 2 µL gel loading buffer. 2) Placed in Agilent Tapestation 4200 using D1000 high resolution tape. 3) Gel image was automatically generated by the Agilent software.