title: DNA of a human hepatitis B virus candidate.
abstract: Particles containing DNA polymerase (Dane particles) were purified from the plasma of chronic carriers of hepatitis B antigen. After a DNA polymerase reaction with purified Dane particle preparations treated with Nonidet P-40 detergent, Dane particle core structures containing radioactive DNA product were isolated by sedimentation in a sucrose density gradient. The radioactive DNA was extracted with sodium dodecyl sulfate and isolated by band sedimentation in a preformed CsCl gradient. Examination of the radioactive DNA band by electron microscopy revealed exclusively circular double-stranded DNA molecules approximately 0.78 mum in length. Identical circular molecules were observed when DNA was isolated by a similar procedure from particles that had not undergone a DNA polymerase reaction. The molecules were completely degraded by DNase 1. When Dane particle core structures were treated with DNase 1 before DNA extraction, only 0.78-mum circular DNA molecules were detected. Without DNase treatment of core structures, linear molecules with lengths between 0.5 and 12 mum, in addition to the 0.78-mum circles were found. These results suggest that the 0.78-mum circular molecules were in a protected position within Dane particle cores and the linear molecules were not within core structures. Length measurements on 225 circular molecules revealed a mean length of 0.78 +/- 0.09 mum which would correspond to a molecular weight of around 1.6 x 10(6). The circular molecules probably serve as primer-template for the DNA polymerase reaction carried out by Dane particle cores. Thermal denaturation and buoyant density measurements on the Dane particle DNA polymerase reaction product revealed a guanosine plus cytosine content of 48 to 49%.
mesh_terms: D002499:Centrifugation, Density Gradient; D003596:Cytosine / Q000032:analysis; D004254:DNA Nucleotidyltransferases / Q000378:metabolism; D004270:DNA, Circular / Q000032:analysis; D004279:DNA, Viral / Q000032:analysis* / Q000096:biosynthesis; D006151:Guanosine / Q000032:analysis; D006515:Hepatitis B virus / Q000032:analysis* / Q000201:enzymology; D006358:Hot Temperature; D008854:Microscopy, Electron; D008970:Molecular Weight; D009691:Nucleic Acid Denaturation; D009711:Nucleotides / Q000378:metabolism; D014316:Tritium
chemical_list: D004270:DNA, Circular; D004279:DNA, Viral; D009711:Nucleotides; D014316:Tritium; D006151:Guanosine; D003596:Cytosine; D004254:DNA Nucleotidyltransferases