Inhibition of reverse transcription in rat liver intracisternal A-particles by thymidine derivatives

AbstractThe thymidine derivatives araAzT, dTTP(3′N3), TTP(3′NH2), and araTTP(3′N3), were studied as inhibitors of the reverse transcription taking place within endogenous retroviral A-type particles, where retroviral RNAs served as templates and primers. dTTP(3′N3) was shown to be the most efficient inhibitor of retroviral particle reverse transcription. Termination of DNA chain elongation is the basic mechanism of the inhibitory action of dTTP(3′N3). The compound has a very low inhibitory effect on mammalian DNA-dependent DNA polymerases α, β and γ

Effect of triphosphate modifications in 2′-deoxynucleoside 5′-triphosphates on their specificity towards various DNA polymerases

AbstractSome natural and glycon-modified dNTPs with β,γ-pyrophosphate substitution at the triphosphate residue were synthesized and studied to evaluate the effect of these modifications on substrate properties of dNTPs in DNA synthesis catalyzed by human placental DNA polymerases α and β, avian myeloblastosis virus reverse transcriptase, and calf thymus terminal deoxynucleotidyl transferase. Reverse transcriptase proved to be the enzyme least specific to such modifications; the substrate activity of β,γ-methylenediphosphonate substituted dTTP and 3′-azido-3′-deoxy-dTTP decreased in the following order: CF2=CHF>CBr2>CFMe≫CH2. This order is individual for each DNA polymerase. It is interesting to mention that β,γ-CBr2 substituted dTTP is neither a substrate nor an inhibitor of DNA polymerase β. This specificity distinguishes DNA polymerase β from other DNA polymerases studied

Selectivity of DNA polymerases toward α and β nucleotide substrates of d and l series

AbstractThe substrate properties of four carbocyclic d and l nucleoside 5′-triphosphate analogs toward HIV and AMV reverse transcriptases and terminal deoxynucleotidyl transferase were evaluated. The compounds of the d-β and l-β series were found to be terminating substrates for these enzymes, while the derivatives of the d-α and l-α series were recognized only by terminal deoxynucleotidyl transferase, suggesting that for the template-independent enzyme the mutual orientation of the two fragments is of no significance. A hypothesis for binding of nucleotides to the DNA polymerase active center was proposed