title: Covalently closed circles of adenovirus 5 DNA.
abstract: The genome of adenoviruses is a double-stranded linear DNA molecule with inverted terminal repeats about 100 base pairs (bp) in length and a terminal protein covalently linked to the 5' nucleotide of each strand. Both of these features permit the formation of DNA circles, the inverted repeats allowing the circularization of single-stranded DNA and the terminal protein the joining of one or more molecules to yield double-stranded circles or concatemers. However, although the existence of covalently closed circles has been postulated, double-stranded viral DNA purified from virions or infected cells by conventional methods (that is, using proteases and phenol or chloroform) has always been obtained in a linear form. Here, we present evidence for the existence in adenovirus 5 (Ad5) infected cells of novel structures resulting from covalent head-to-tail joining of viral DNA molecules and show that these structures are due at least in part to the formation of covalently closed circles.
mesh_terms: D000256:Adenoviridae / Q000235:genetics*; D000818:Animals; D002472:Cell Transformation, Viral; D002499:Centrifugation, Density Gradient; D004270:DNA, Circular / Q000032:analysis*; D004279:DNA, Viral / Q000032:analysis*; D004587:Electrophoresis, Agar Gel; D004591:Electrophoresis, Polyacrylamide Gel; D009690:Nucleic Acid Conformation
chemical_list: D004270:DNA, Circular; D004279:DNA, Viral