Nucleoprotein complexes harboring an extrachromosomal DNA closely related to 7 S DNA of avian myeloblastosis virus: physico-chemical properties and representation of nucleic acids.
The source of avian myeloblastosis virus (AMV) DNA, an extrachromosomal small polydisperse DNA, present in the material forming the postmicrosomal sediment (POMS) of lysed chicken leukemic myeloblasts (CHLMs) is organized into nucleoprotein (NP) complexes containing always RNA. This material, radioactively double-labelled for DNA and RNA, separated in isopycnic sucrose gradients into three POMS components (A,B,C) differing from one another in properties of labelling for DNA and RNA, sucrose densities (1.21, 1.18 and 1.08 g/cm3 for components A, B and C, respectively) and sedimentation properties of NP complexes which constituted the individual POMS components. The NP complexes present in representative fractions of POMS components A, B and C sedimented at 37.3 and 27.3, at 15.3 and 7.4, and at 11.3 and 5.5, respectively. They differed also in the length of DNAs they were harboring. Radioactively double-labelled nucleic acids (NAs) of POMS components A, B and C sedimented at 9, 7 and 3.5 S, respectively, and the sedimentation characteristics of both labels corresponded with those significant for replication intermediates. Electrophoretic characteristics of these NAs indicated that we dealt with DNA and RNA products of a lagging DNA strand synthesis (LSS) taking place, evidently, on pieces of the lagging sites of replicating DNA strands that were cut out at predicted sites by nucleases. As regards the origin of AMV DNA, we show that the major and minor portions of this DNA might be descending from NAs harbored in NP complexes of POMS components B and C, respectively, pointing out selectivity of segregation of this DNA from the cell into AMV core.
Ríman
J
J
Institute of Molecular Genetics, Academy of Sciences of the Czech Republic, Praha, Czech Republic.
Sulová
A
A
D000818:Animals; D009189:Avian Myeloblastosis Virus / Q000235:genetics*; D002250:Carbon Radioisotopes; D002499:Centrifugation, Density Gradient; D002645:Chickens; D004275:DNA, Ribosomal / Q000378:metabolism; D004279:DNA, Viral; D004587:Electrophoresis, Agar Gel; D009696:Nucleic Acids; D009698:Nucleoproteins / Q000378:metabolism*; D012313:RNA; D014316:Tritium
D002250:Carbon Radioisotopes; D004275:DNA, Ribosomal; D004279:DNA, Viral; D009696:Nucleic Acids; D009698:Nucleoproteins; D014316:Tritium; D012313:RNA