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Reverse Transcriptase

To develop anti-HIV agent, major effort have been devoted to develop inhibitors that   interfere with the normal activity of one of the three key enzymes in the HIV virus: protease, integrase and reverse transcriptase. HIV reverse transcriptase (HIV RT) among the three is an excellent target for drug design as it is essential only for HIV replication, but not required for normal cell replication. HIV RT is a DNA polymerase that transforms single strand rRNA to double strand DNA. HIV RT inhibitors reduce the ability of the enzyme to perform RNA-dependent DNA polymerase and RNaseH activities, required for the conversion of viral RNA to DNA. Because viral DNA copies are necessary for subsequent replication steps, inhibition of HIV RT forms an important part of anti-HIV therapies . HIV RT inhibitors could be classified into two broad categories: the first, termed as nucleoside (or nucleotide) reverse transcriptase inhibitors (NRTIs). They compete with the natural deoxynucleotides for incorporation into the growing DNA chain of HIV virus and hence they are also referred as competitive HIV inhibitors. As they lack a 3'-OH group on the deoxyribose moiety, upon incorporation of such NRTI into growing DNA, the consecutive next deoxynucleotide is unable to make 5'-3' phosphodiester bond required to extend the DNA chain and this terminates viral DNA synthesis. The second class, non nucleoside reverse transcriptase inhibitors (NNRTIs), instead binds to a hydrophobic pocket on HIV RT, which allosterically alters the confirmation of active site residues, hampering normal enzymatic activity. NNRTIs are especially attractive drug candidates and comprises of highly specific and structurally diverse set of drugs. They noncompetitively inhibit normal RT function, which makes them less likely to interfere with the normal function of other DNA polymerases and therefore less toxic than nucleoside inhibitors (NRTIs). AZT (azidothymidine, zidovudine or Retrovir), is one such popular drug. The structure of HIV-1 RT bound to a short 18/19-mer DNA oligonucleotide duplex and complexed with an antibody Fab portion was reported shortly thereafter (RT-DNA cocrystal) . There are now three structures of the unliganded enzyme, and recent reports have described additional RT structures that contain other nonnucleoside inhibitors.

Ribbon diagram of the HIV-1 RT bound to a space-filling model of an 18–19-base duplex oligonucleotide substrate. The regions of A-form, B-form, and bent DNAs are indicated. The active site amino acids of the DNA polymerase and RNase H (which are both present in the p66 subunit) are shown in white

References :
  1. Mitsuya, H., Yarchoan, R., Broder, S., Molecular Targets For Aids Therapy. Science 1990, 249, 1533-1544,Katz,RA., Skalka,AM, The Retroviral Enzymes, Annu. Rev. Biochem., 1994, 63, 133-173.

  2. K. Das, S. G. Sarafianos, E. Arnold and S. H. Hughes, Encyclo. Biol. Chem. 388-392 (2004) Elsevier Eds. W. J. Lennarz and M. D. Lane. HIV-1 Reverse Transcriptase Structure  doi:10.1016/B0-12-443710-9/00179-4

  3. Tantilo, C., Ding, JP.; Jacobomolina, A., Nanni, R.G., Boyer, PL., Hughes, SH., Pauwels, R., Andries, K., Janssen, PAJ., Arnold, E., Locations of Anti-Aids Drug Binding Sites and Resistance Mutations in the 3-Dimensional Structure of HIV-1 Reverse Transcriptase : Implications For Mechanisms of Drug Inhibition and Resistance. J. Mol. Biol., 1994, 243, 369-387.

  4. M.-P. de Béthune, Antiviral Rese., 85, 2010, 75-90 Twenty-five Years of Antiretroviral Drug Development: Progress and Prospects

  5. Declercq, E., HIV Resistance to Reverse Transcriptase Inhibitors. Biochem.Pharmacolo. 1994, 47, 155-169.

  6. Declercq, E., HIV Resistance to Reverse Transcriptase Inhibitors. Biochem.Pharmacolo. 1994, 47, 155-169.

  7. Kopp EB., Miglietla, J.J., Shrutkowski, A.G., Shih CK., Grob PM.,Skoog, MT., Steady state kinetics and inhibition of HIV-1 reverse transcriptase by a non-nucleoside dipyridodiazepinone., BI-RG-587, using a heteropolymeric template. Nucleic Acids Res., 1991, 19, 3035-3039.

  8. Romero, DL., Bussa, M., Tan, CK., Reusser, F., Palmer, JR., Poppe, SM., Aristoff, PS., Downery, KM., So AG., Resnick, L., Tarpley, WG., Nonnucleoside Reverse Transcriptase Inhibitors That Potently and Specifically Block Human Immunodeficiency Virus Type I Replication., Proc. Natl. Acad. Sci. USA, 1991, 88, 8806-8810.

  9. Jacobo-Molina et al. 1991,1993; Arnold et al. 1992.

  10. Esnouf et al. 1995;Rodgers et al. 1995;Hsiou et al. 1996

  11. Ding et al. 1995a,b;Ren et al. 1995.