Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00492 (hypoxanthine-guanine phosphoribosyltransferase)
 2,385 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The frequency of 6-thioguanine resistant (TGr) mutants induced in human G0 phase T-lymphocytes by 200 cGy of gamma irradiation is greatly enhanced by incubation with cytosine arabinoside (ara-C) after irradiation. The mutant frequency increased with increasing incubation time in ara-C for up to 2 hr. This mutation induction required a phenotypic expression time of 5-8 days mass culture growth, similar to that found with mutants induced by 300 cGy of irradiation alone. Southern blot analysis of 40 isolated mutant clones revealed 8 independent mutations by T-cell receptor (TCR) gene rearrangement patterns. Four of these eight showed hprt gene structural alterations (0.50). An alternative method to allow phenotypic expression was developed to minimize the isolation of hprt/TCR sibling mutants. The use of in situ expression in the microtiter dish wells resulted in the isolation of 17 independent mutations in 19 mutant clones. Ten of these 17 mutations showed hprt structural alterations (0.59). The high fraction of mutations involving structural alterations detected by Southern blot analysis is consistent with the known induction of chromosome aberrations by irradiation plus ara-C treatment. We propose that both the increase in Mf and the increase in the incidence of hprt gene structural alterations are due to the accumulation of strand breaks in repairing regions of DNA under these conditions of ara-C induced inhibition of repair. We further propose that upon release of the ara-C inhibition, these repairing regions can interact to yield both gene mutations and chromosome aberrations.
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PMID:Cytosine arabinoside enhancement of gamma irradiation induced mutations in human T-lymphocytes. 205 Jan 30

The lack of de novo purine biosynthesis in many parasitic protozoans makes the enzymes in the salvage of purines attractive chemotherapeutic targets. Hypoxanthine-guanine phosphoribosyltransferase (HGPRT) is a key enzyme for purine salvage and bacterial complementation screens for HGPRT inhibitors are known. The low KMS for purine bases makes purine analogs unattractive as competitive inhibitors for this enzyme. Despite the availability of many crystal structures of HGPRTs, it is only recently that selective inhibitors of the enzyme have been developed. Therefore, novel purine analogs which act as substrates for the HGPRT reaction and thereby inhibit downstream enzymes or get incorporated into the nucleotide pool are an attractive altenative for drug design. We have used a combination of two E. coli strains Sphi606 (ara, deltapro-gpt-lac, thi, hpt) and Sphi609 (ara, deltapro-gpt-lac, thi, hpt, pup, purH,J, strA) to identify inhibitors and substrates of HGPRT. E. coli Sphi609 is deficient in both de novo synthesis as well as salvage enzymes of purine nucleotide synthesis, while E. coli Sphi606 is deficient in salvage enzymes only. Hence, expression of functional HGPRTs in E. coli Sphi606 grown in minimal medium makes it susceptible to HGPRT substrates, which inhibit downstream processes. Growth of E. coli Sphi609 in minimal medium can be made conditional for the expression of a functional HGPRT and this growth would be susceptible to both HGPRT substrate analogs and inhibitors. A substance that strictly acts as an inhibitor will affect growth of transformed E. coli Sphi609 only. For this purpose, we compared the human and P. falciparum enzymes with known HGPRT substrate analogs. Our data with 6-mercaptopurine, 6-thioguanine and allopurinol show that these compounds act by being substrates for HGPRT. Our results with allopurinol suggest that it is a better substrate for P. falciparum HGXPRT than the human enzyme. Therefore, species-specific substrates can be tested out successfully in E. coli Sphi606. The formation of products from substrates like allopurinol lacking a labile proton at N7 raises the possibility that the deprotonation of substrates might occur at N9 rather than at N7 or a purine anion might be the true substrate for the reaction.
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PMID:Development of a bacterial screen for novel hypoxanthine-guanine phosphoribosyltransferase substrates. 1154 74