Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.26.4 (RNase H)
 2,751 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The replicative cycle of the human immunodeficiency virus (HIV) is reviewed, and currently used and investigational agents directed against the virus are discussed. The first step in the replication of HIV is selective binding of the envelope glycoprotein to CD4 receptors located on T lymphocytes. The virion is then uncoated within the cytoplasm, yielding viral genomic RNA. Reverse transcriptase uses the viral RNA as a template to form single-stranded DNA, which is duplicated to form proviral DNA through the activity of ribonuclease H. Host RNA polymerases transcribe the integrated proviral DNA into messenger RNA, and there is subsequent translation to viral proteins. After translation, further modification of precursor polyproteins is necessary to produce functional peptides. The assembled virus then buds from the cell surface and invades other cells. Targets of drug intervention in the replicative cycle include (1) binding and entry, (2) reverse transcriptase, (3) transcription and translation, and (4) viral maturation and budding. Inhibitors of binding and entry include recombinant soluble CD4, immunoadhesins, peptide T, and hypericin. Nucleoside reverse-transcriptase inhibitors include zidovudine, didanosine, zalcitabine, and stavudine. Foscarnet, tetrahydroimidazobenzo-diazepinthione compounds, and nevirapine are some nonnucleoside reverse-transcriptase inhibitors. Inhibitors of transcription and translation include antagonists of the tat gene and GLQ223. Castanospermine, N-butyldeoxynojirimycin, and protease inhibitors interfere with viral maturation and budding. Drug combinations that have been or are being investigated include zidovudine plus interferon alfa, zidovudine plus zalcitabine, and zidovudine plus didanosine. Four agents currently have approved labeling for use against HIV infection: zidovudine, didanosine, zalcitabine, and stavudine. Monotherapy with zidovudine remains the treatment of first choice. Although progress has been made in developing drug therapies for HIV infection, more selective and more potent drugs are urgently needed. The best approach at present is to optimize the use of available agents, continue to investigate new therapies, and educate the public about prevention.
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PMID:Agents for treating human immunodeficiency virus infection. 775 75

Of the HIV proteins, reverse transcriptase(RT) has been probably the most useful target protein for screening and designing of its specific inhibitors. Because retroviral replication is absolutely dependent on both the RNase H and the polymerase function of RT and, so far as is now known, RT does not play a direct role in the life cycle of a normal cell. Under suitable fermentation conditions in our experiments, HIV-1 RT was highly expressed in E. coli JM109(pKRT-2)* by inducing the trc promoter with isopropyl-beta-Dthiogalactopyranoside(IPTG). 1. 1 mg of purified RT was obtained from one liter culture of bacteria by DEAE-cellulose and phosphaellulose chromatography. SDS-PAGE analysis of the purified RT showed two major protein bands of 66 kD and 51 kD, indicating that the purified RT was a heterodimer composed of two subunits. Results of enzyme assay showed that the purified RT had high activity(1.4 x 10(4) umit/mg). We also improved the reaction system of enzyme assay. The effect of PFA on HIV-1 RT was determined with the improved enzyme assay and the mechanism of inhibition was non-competitive with respect to substrate consistent with the reports of Dr. Bo Oberg. This suggests that the purified HIV-1 RT by this simple method can be applied to the anti HIV-1-drug screening. (*E. coli JM109(pKRT2) was obtained from NIAID, NIH; pKRT2 from Dr. Richard D'Aquila and Dr. William C. Summers.)
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PMID:[The study on purification and characterization of HIV-1 reverse transcriptase from a recombinant strain of E. coli]. 1251 92