Effect of a thiobenzimidazolone derivative on DNA strand transfer catalyzed by HIV-1 reverse transcriptase.
Thiobenzimidazolone (TIBO) derivatives are known inhibitors of the DNA polymerase activity of human immunodeficiency virus type 1 (HIV-1) reverse transcriptase (RT). The effect of a TIBO derivative ((+)-S-4,5,6,7-tetrahydro-9-chloro-5- methyl-6-(3-methyl-2-butenyl)-imidazol[4,5,1-jk]1,4-benzodiazapine -2-thione ) on the DNA strand transfer reaction catalyzed by HIV-1 RT (which is a function of both the DNA polymerase and RNase H activities) was investigated by delineating the effect of the drug on the constitutive DNA polymerase and RNase H activities) was investigated by delineating the effect of the drug on the constitutive DNA polymerase and RNase H activities. Single nucleotide incorporation on template-primer 1 was used to study the DNA polymerase activity of HIV-1 RT while template-primer 2 was used to study the effect of TIBO on the RNase H activity (polymerase independent). The drug was found to decrease the amplitude of the presteady-state burst when preequilibrated with the enzyme-substrate complex besides decreasing the steady-state rate of single nucleotide incorporations. In the absence of preincubation, TIBO did not affect the burst amplitude but decreased the steady-state rate after the pre-transient phase. This suggested that binding of TIBO to RT was affected by the presence of template-primer and required dissociation of the enzyme from the template-primer for effective binding. The polymerase-independent RNase H activity was activated in the presence of TIBO. The effect of TIBO on the overall process of DNA strand transfer is a balance between its inhibition of the polymerase activity and its activation of the RNase H activity.
Gopalakrishnan
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Department of Chemistry, Pennsylvania State University, University Park 16802.
Benkovic
S
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D000998:Antiviral Agents / Q000494:pharmacology; D001483:Base Sequence; D001569:Benzodiazepines / Q000494:pharmacology*; D004247:DNA / Q000378:metabolism*; D017931:DNA Primers / Q000737:chemistry; D054303:HIV Reverse Transcriptase; D015497:HIV-1 / Q000201:enzymology; D007093:Imidazoles / Q000494:pharmacology*; D008969:Molecular Sequence Data; D018894:Reverse Transcriptase Inhibitors; D016914:Ribonuclease H / Q000378:metabolism; D013698:Templates, Genetic
D000998:Antiviral Agents; D017931:DNA Primers; D007093:Imidazoles; D018894:Reverse Transcriptase Inhibitors; D001569:Benzodiazepines; C067413:R-82913; D004247:DNA; D054303:HIV Reverse Transcriptase; D016914:Ribonuclease H