Identification of intranuclear structures containing the 72K DNA-binding protein of human adenovirus type 5

Immunocytochemical techniques have been applied to cells infected with human adenovirus type 5 in order to study the distribution of antigens related to the virus-encoded Mr = 72000 (72K) DNA-binding protein. In embedded cells 72K antigen was found to be associated with 'clear' fibrillar inclusions, in which viral DNA replication is known to take place. "Dense" fibrillar inclusions, which are thought to contain previously replicated viral DNA, do not contain detectable levels of 72K antigen, suggesting that the conversion of clear inclusions to dense inclusions is accompanied by loss of the 72K protein. In cells examined by the spreading technique of Miller, 72K antigen is associated with the 10 nm "thick filaments" previously described by several laboratories, consistent with the established role of the 72K protein in viral replication complexes.