Important note: Information in this article was accurate in 1991. The state of the art may have changed since the publication date.
2',3'-DIDEOXYCYTIDINE AND HUMAN IMMUNODEFICIENCY VIRUS REVERSE TRANSCRIPTASE
Diss Abstr Int [B]; 50(1):117 1989. Unique Identifier : AIDSLINE ICDB/90658142 Starnes MC; Univ. of North Carolina, Chapel Hill
Abstract:
2',3'-Dideoxycytidine (ddCyd) is a candidate for clinical trial in the treatment of AIDS, as a result of its potent inhibition of HIV replication. The cellular metabolism and cytotoxicity of ddCyd are discussed, as well as the interaction of ddCTP and other nucleotide and pyrophosphate analogs with mammalian DNA polymerases and HIV reverse transcriptase (RT). In addition, some structural and functional characteristics of HIV RT are described. 5 uM ddCyd reduced Molt 4 cell division by 50% during a 48-hr continuous exposure; however, a 24-hr exposure to 0.5 uM ddCyd reduced clonogenic survival by 50%. [14C]-dThd incorporation into DNA was reduced during exposure to ddCyd. Acid-soluble ddCyd metabolites were ddCMP (30%), ddCDP (10%), and ddCTP (40%). Initial ddCyd phosphorylation was catalyzed primarily by cytoplasmic dCyd kinase (Km 180 uM), and ddCyd was not a substrate for human Cyd-dCyd deaminase. Metabolism of ddCyd was identical in mock and HIV-infected H9 cells. Inhibition by ddCTP of dCTP incorporation into gapped duplex DNA by polymerases alpha, beta, gamma, and HIV RT was competitive with dCTP, and Ki values were 110, 2.6, 0.016, and 0.10 uM, respectively. Incorporation of ddCMP into Molt 4 DNA was observed, and polymerases beta, gamma, and HIV RT were able to utilize ddCTP as a substrate. Exonucleases associated with polymerases alpha and gamma were able to remove ddCMP from DNA. Immunoaffinity-purified HIV reverse transcriptase consisted of two polypeptides, p66 and p51, in approx equal proportions. After denaturing polyacrylamide gel electrophoresis and protein renaturation, p66 alone was sufficient for both DNA and-RNA directed DNA polymerization. Subunit structure may contribute to p66 catalytic activity, since the apparent mol wt of native HIV RT was greater than 97.5 kD, and since recovery of p66 catalytic activity was 10% that of DNA polymerase beta. Inhibition of mammalian DNA polymerases and HIV RT by other dideoxynucleotides and several pyrophosphate analogs was examined. The selectivity and potential cytotoxicity of these compounds are discussed in comparison with ddCTP. (Full text available from University Microfilms International, Ann Arbor, MI, as Order No. AAD89-05684)
Keywords: Gene Expression Regulation, Viral/DRUG EFFECTS Human HIV/*DRUG EFFECTS/GENETICS RNA-Directed DNA Polymerase/*ANTAGONISTS & INHIB Virus Replication/*DRUG EFFECTS Zalcitabine/*PHARMACOLOGY THESIS 910228
M9120716
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Important note: Information in this article was accurate in 1991. The state of the art may have changed since the publication date.
