Transcription of the 5'-terminal cap nucleotide by RNA-dependent DNA polymerase: possible involvement in retroviral reverse transcription.
The possible transcription of the 5'-terminal cap nucleotide of mRNA by RNA-dependent DNA polymerase was examined by a single-step assay, based on the generation of a hairpin structure during reverse transcription of globin mRNA. Using this approach, we demonstrated that the 5'-terminal cap nucleotide of mRNA is indeed transcribed by RNA-dependent DNA polymerase into a 3'-terminal residue of cDNA and were able to measure the extent of such transcription. The observed transcription of the cap nucleotide raises a number of questions that may be addressed using the relatively simple single-step assay employed in the present study. Cap nucleotide transcription by RNA-dependent DNA polymerase may have important implications for our understanding of the mechanism of action of reverse transcriptases. It may represent a selection mechanism for only partial transcription of the 5' repeat element of viral RNA genome, thus generating a RNA fragment that may play a role in priming of second (plus) DNA strand during retroviral reverse transcription. Moreover, the demonstrated ability of complementary nucleotides to form hydrogen bonds, even when in a parallel orientation, may have interesting and important consequences.
Boston Biomedical Research Institute, MA 02114, USA.
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Schweitzer
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D000818:Animals; D009189:Avian Myeloblastosis Virus / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D017931:DNA Primers; D018076:DNA, Complementary; D005914:Globins / Q000235:genetics; D051379:Mice; D008807:Mice, Inbred BALB C; D008969:Molecular Sequence Data; D009690:Nucleic Acid Conformation; D012333:RNA, Messenger / Q000737:chemistry / Q000235:genetics; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*; D014158:Transcription, Genetic
D017931:DNA Primers; D018076:DNA, Complementary; D012333:RNA, Messenger; D005914:Globins; D012194:RNA-Directed DNA Polymerase