Reverse transcriptase sources

Up to this point, GIPF expressions have been formulated for only one type of biological activity - the inhibition of reverse transcriptase (RT), the enzyme that promotes the reverse transcription of genomic RNA into double-stranded DNA, a key step in the replication of the human immunodeficiency virus, HIV [82, 87]. Analytical representations were obtained for the anti-HIV potencies of three families of RT inhibitors the correlation coefficients are between 0.930 and 0.952. We are currently investigating the effects of applying the GIPF approach to certain portions of the molecules rather than their entireties. This might reveal the source of the activity, or alternatively, indicate it to be delocalized. 

Nearly 40 million people are infected with the human immunodeficiency virus (HIV). Over half of those infected reside in sub-Saharan Africa. Worldwide during 2004, it is estimated that nearly 14,000 people a day were infected. Human immunodeficiency virus type 1 is the primary etiological source for the acquired immunodeficiency syndrome (AIDS). Fortunately, people infected with HIV are leading longer and more productive lives due to the availability of more effective therapies. Better medicines have evolved due to the efforts of scientists worldwide who find targets and compounds that inhibit the virus life-cycle. The current treatment for HIV infection is via a drug cocktail that usually includes a protease inhibitor (PI), a nucleoside reverse transcriptase inhibitor (NRTI), and a non-nucleoside reverse transcriptase inhibitor (NNRTI). 

Some well-characterized eukaryotic DNA transposons from sources as diverse as yeast and fruit flies have a structure very similar to that of retroviruses these are sometimes called retrotransposons (Fig. 26-33). Retro-transposons encode an enzyme homologous to the retroviral reverse transcriptase, and their coding regions are flanked by LTR sequences. They transpose from one position to another in the cellular genome by means of an RNA intermediate, using reverse transcriptase to make a DNA copy of the RNA, followed by integration of the DNA at a new site. Most transposons in eukaryotes use this mechanism for transposition, distinguishing them from bacterial transposons, which move as DNA directly from one chromosomal location to another (see Fig. 25-43). 

To identify relevant IgE binding components from natural source extracts, various techniques like IgE immunoscreening of expression cDNA libraries, reverse transcriptase polymerase chain reaction (PCR), or phage-display technology combined with immunoscreening are used (Wallner et al. 2004). 

One strategy to address these problems is to develop antiretroviral drugs with targets other than reverse transcriptase and protease. In the collaboration of our laboratories at the University of North Carolina and Panacos Pharmaceuticals, we have taken advantage of the huge molecular diversity found in natural products. Plants are a major source of biologically active compounds and can provide good leads that are structurally unique and/or have new mechanisms of action. 

The interpretation of genotypic resistance testing is complex. The interpretation of resistance mutations uses rules-based software that takes into account crossresistance and interactions of mutations. The commercially available systems generate a summary report that lists the various mutations that have been identified in the reverse transcriptase and protease genes, and each drug is reported as resistant, possibly resistant, no evidence of resistance, or insufficient evidence. A comprehensive discussion of the specific mutations associated with each antiretroviral drug and the interactions of mutations is beyond the scope of this chapter, but is available firom a variety of sources (http //hiv-web.lanl.gov/content/index, http //www.iasusa. org., http //hivdb.standford. edu/). 

Ribonucleic acid is a difficult nucleic acid to work with because it is very sensitive to RNases that are prevalent in the lab (your hands are a good source of RNases ) and the techniques for sequencing RNA are indirect. To circumvent these problems, mRNA can be converted into cDNA using an enzyme called reverse transcriptase (Chapter 30). Reverse transcriptase is an RNA-dependent DNA polymerase that uses an RNA template to synthesize cDNA. The single-stranded cDNA... 

Reverse transcriptase is an enzyme that uses a single-stranded RNA template and makes a DNA copy (Fig. 13.20). The RNA template can be transcribed from DNA by RNA polymerase or obtained from another source, such as an RNA virus. The DNA copy of the RNA produced by reverse transcriptase is known as complementary DNA (because it is complementary to the RNA template), or cDNA. Retroviruses (RNA viruses) contain a reverse transcriptase, which copies the viral RNA genome. A double-stranded cDNA is produced, which can become integrated into the human genome (see Fig. 12.23). After integration, the viral genes may be inactive, or they may be transcribed, sometimes causing diseases such as AIDS or cancer (see Chapter 18). 

Recently, work in the laboratories of Che [ 183] found that tosylhydrazone derivatives could be used as a carbene source for cyclopropanation catalyzed by rutheniiun porphyrins. The practical utility of these ruthenium catalysts was illustrated in the synthesis of a potent HIV-reverse transcriptase inhibitor. 

Pengsuparp T, Cai L, Constant H et al (1995) Mechanistic evaluation of new plant-derived compounds that inhibit HIV-1 reverse transcriptase. J Nat Prod 58 1024—1031 Perry NB, Berm MH, Brennan NJ et al (1999) Antimicrobial, antiviral and cytotoxic activity of New Zealand lichens. Lichenologist 31 627-636 Petrzik K, Vondrak J, Bartak M et al (2014) Lichens—a new source or yet unknown host of herbaceous plant viruses Eur J Plant Pathol 138 549-559 Rankovic B, Misic M, Sukdolak S (2007a) Antimicrobial activity of the lichens Cladoniafurcata, Parmelia caperata, Parmeliapertusa, Hypogymnia physodes and Umbilicariapolyphylla. Br J Biomed Sci 64 143-148... 

Alteromonas infernus act as sources for antiviral compounds. Sulphated EPS are known to interfere with the adsorption and penetration of viruses into host cells, as well as inhibiting various retroviral reverse transcriptases. TVvo new exopolysaccharides, EPS-1 and EPS-2, isolated from Bacillus licheniformis and Geobacillus thermodenitrificans, are very effective in the control of HSV (Arena et al., 2009). Macrolactin A is another antiviral compound derived from marine bacteria that inhibited HIV replication (Gustafson et al, 1989). 

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