title: In situ structural organization of encapsidated and unencapsidated Ectromelia virus DNA.
abstract: The structural organization of Ectromelia virus DNA in infected mouse liver cells has been studied by using thin sections stained with the Feulgen-like osmium-ammine reaction. We found that in the cytoplasmic factories, free viral DNA was structured into completely extended filaments 2-3 nm thick. Viral DNA in immature virions, however, appeared to have a structural organization that superimposed that of eukaryotic chromatin. This was constituted by roundish subunits, with a diameter of 11-13 nm, composed of a DNA ring encircling an unstained inner core. The mature virion was composed of the same type of subunits, which were arranged in threads twisted into a figure 8 configuration. The distribution of basic proteins was also investigated with the acrolein silver-methenamine technique. In the viral particles only nucleoids were stained; a uniformly distributed positive reaction was observed in the cytoplasmic factories.
mesh_terms: D000818:Animals; D002213:Capsid / Q000378:metabolism*; D002843:Chromatin / Q000648:ultrastructure; D004279:DNA, Viral / Q000378:metabolism / Q000648:ultrastructure*; D004481:Ectromelia virus / Q000648:ultrastructure*; D008099:Liver / Q000382:microbiology* / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D009690:Nucleic Acid Conformation; D011487:Protein Conformation
chemical_list: D002843:Chromatin; D004279:DNA, Viral