Rapid Screening of HIV Reverse Transcriptase and Integrase Inhibitors

Although a number of anti HIV drugs have been approved, there are still problems with toxicity and drug resistance. This demonstrates a need to identify new compounds that can inhibit infection by the common drug resistant HIV-1 strains with minimal toxicity. Here we describe an efficient assay that can be used to rapidly determine the cellular cytotoxicity and efficacy of a compound against WT and mutant viral strains.The desired target cell line is seeded in a 96-well plate and, after a 24 hr incubation, serially dilutions of the compounds to be tested are added. No further manipulations are necessary for cellular cytotoxicity assays; for anti HIV assays a predetermined amount of either a WT or drug resistant HIV-1 vector that expresses luciferase is added to the cells. Cytotoxicity is measured by using an ATP dependent luminescence assay and the impact of the compounds on infectivity is measured by determining the amount of luciferase in the presence or the absence of the putative inhibitors.This screening assay takes 4 days to complete and multiple compounds can be screened in parallel. Compounds are screened in triplicate and the data are normalized to the infectivity/ATP levels in absence of target compounds. This technique provides a quick and accurate measurement of the efficacy and toxicity of potential anti HIV compounds.     

Nucleoside and Nucleotide Inhibitors of Inosine Monophosphate (IMP) Dehydrogenase as Potential Antitumor Inhibitors

Abstract

A review of various nucleoside and nucleotide inhibitors of IMP dehydrogenase suggests that such inhibitors may also exhibit significant antitumor effects. The details of the precise mode of action and structure activity relationships remain to be established. This new area of research should prove fruitful for uncovering useful and more specific antitumor agents.     

An Analysis of Enzyme Kinetics Data for Mitochondrial DNA Strand Termination by Nucleoside Reverse Transcription Inhibitors

Nucleoside analogs used in antiretroviral treatment have been associated with mitochondrial toxicity. The polymerase-γ hypothesis states that this toxicity stems from the analogs'' inhibition of the mitochondrial DNA polymerase (polymerase-γ) leading to mitochondrial DNA (mtDNA) depletion. We have constructed a computational model of the interaction of polymerase-γ with activated nucleoside and nucleotide analog drugs, based on experimentally measured reaction rates and base excision rates, together with the mtDNA genome size, the human mtDNA sequence, and mitochondrial dNTP concentrations. The model predicts an approximately 1000-fold difference in the activated drug concentration required for a 50% probability of mtDNA strand termination between the activated di-deoxy analogs d4T, ddC, and ddI (activated to ddA) and the activated forms of the analogs 3TC, TDF, AZT, FTC, and ABC. These predictions are supported by experimental and clinical data showing significantly greater mtDNA depletion in cell culture and patient samples caused by the di-deoxy analog drugs. For zidovudine (AZT) we calculated a very low mtDNA replication termination probability, in contrast to its reported mitochondrial toxicity in vitro and clinically. Therefore AZT mitochondrial toxicity is likely due to a mechanism that does not involve strand termination of mtDNA replication.     

FD耐热逆转录酶的部分酶学性质研究

ＦＤ耐热逆转录酶（ＦＤ－ＴＲＴ）来自一株栖热杆菌菌株．通过ＲＴ－ＰＣＲ方法,论文对ＦＤ－ＴＲＴ的部分酶学性质进行了研究．ＦＤ耐热逆转录酶能耐受９５℃的高温,最适反应温度在６５～７５℃左右,这时ＲＮＡ的高级结构能解开,可以提高逆转录反应的效率;同时引物和ＲＮＡ模板识别的专一性强,可大大提高逆转录的特异性．实验表明ＦＤ－ＴＲＴ逆转录反应的最适条件为：２５ｍｍｏｌ／ＬＴｒｉｓ－ＨＣｌ（ｐＨ８．８,１５ｍｍｏｌ／Ｌ（ＮＨ４）２ＳＯ４,１００μｇ／ｍｌ明胶,５００μｍｏｌ／ＬｄＮＴＰｓ,２５ｐｍｏｌ逆转录引物,１ｍｍｏｌ／ＬＭｎＣｌ２,２ＵＦＤ耐热逆转录酶,反应在６５～７０℃下进行．在上述条件下,用ＲＴ－ＰＣＲ可检出少于５ｐｇ外周血总ＲＮＡ中特异的α珠蛋白ｍＲＮＡ．