title: RNA-DNA covalent bonds between the RNA primers and the DNA products formed by RNA tumor virus DNA polymerase.
abstract: Initiation of DNA synthesis by endogenous RNA primer molecules was studied with three different RNA tumor viruses. The influence of the method of virus disruption on the observed RNA-DNA bonds was ascertained. Ether disrupted virions of both murine leukemia virus (MuLV) and the B77 strain of avian sarcoma virus (B77 virus) have rC-dC and rA-dA covalent linkages between RNA primers and newly synthesized DNA. None of the 14 other possible bonds were formed. Ether-disrupted virions of avian myeloblastosis virus (AMV) have rU-dC and rA-dA linkages. In contrast, work reported herein and from other laboratories shows that Nonidet P-40 (NP-40)-disrupted virions of all three viruses have only the rA-dA junction. Studies with virus particles which were first disrupted with ether and then treated with NP-40 indicated that the detergent treatment disallowed the formation of the ribopyrimidine-dC internucleotide bond. The same transfers are found with AMV in the presence or absence of actinomycin D, where only single-stranded DNA is formed. This finding is consistent with the notion that virtually all of the significant primers have been recognized. In contrast to mature virions, transfer experiments with ether-disrupted early harvest (5 min) MuLV showed only the rC-dC bond; the rA-dA bond was absent. The short-time harvest contains a significantly higher proportion of infectious virions than 24-h harvests. Also, since the RNA from early harvest virus is appreciably more homogenous than the RNA of mature MuLV, it is concluded that the ribopyrimidine-dC linkage is the more significant initiation event from a biochemical standpoint.
mesh_terms: D001355:Alpharetrovirus / Q000201:enzymology / Q000378:metabolism*; D001354:Avian Leukosis Virus / Q000201:enzymology / Q000378:metabolism*; D001665:Binding Sites; D002499:Centrifugation, Density Gradient; D055598:Chemical Phenomena; D002621:Chemistry; D002854:Chromatography, Paper; D004254:DNA Nucleotidyltransferases / Q000378:metabolism*; D004279:DNA, Viral / Q000096:biosynthesis*; D003609:Dactinomycin / Q000494:pharmacology; D010761:Phosphorus Radioisotopes; D012367:RNA, Viral / Q000378:metabolism*; D011925:Rauscher Virus / Q000201:enzymology / Q000378:metabolism*; D014316:Tritium; D014529:Uridine / Q000378:metabolism
chemical_list: D004279:DNA, Viral; D010761:Phosphorus Radioisotopes; D012367:RNA, Viral; D014316:Tritium; D003609:Dactinomycin; D004254:DNA Nucleotidyltransferases; D014529:Uridine