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)

Strong evidence points to mutation induction as one mechanism by which changes are introduced into normal cells to convert them into cancer cells. To understand the mechanisms by which mutations are induced in human cells by carcinogens, we are determining the kinds and spectra of mutations induced in the coding region of the hypoxanthine(guanine)phosphoribosyltransferase (hprt) gene. This region, composed of 654 bp, represents nine exons from a 44 kbp gene. To be able to analyze a large number of independent mutants rapidly and economically, we have optimized the conditions for copying mRNA directly from lysates of a small number of cells (e.g., 100) from a 6-thioguanine-resistant clone using reverse transcriptase and oligo(dT)12-18 primers. Then two 20-mer primers, specific for the cDNA of the hprt gene, are used to amplify the first and second strand cDNA 5 x 10(7)-fold during 30 cycles of polymerase chain reaction (PCR). The product (2 to 10 ng) is then purified by ultrafiltration, diluted 1:10, and subjected to an additional 30 cycles of PCR, using two 20-mer primers located just interior to the first set. The amplification product, 5 to 10 ug, is sequenced directly using three other end-labeled primers and Sequenase. To date, we have analyzed 26 mutants induced by (+-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha,epoxy-7,8,9,10-tetrahydrobenzo [a]pyrene and found that 24/26 involved base substitutions. 97% of these involved G.C, predominantly G.C----T.A, distributed over seven exons, with many of the substitutions located in exon 3.
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PMID:Amplification of mRNA of the hprt gene from lysates of mutant human cells and direct DNA sequencing to determine the spectrum of mutations induced by (+/-)-7 beta,8 alpha-dihydroxy-9 alpha,10 alpha, epoxy-7,8,9,10-tetrahydrobenzo[a]pyrene. 211 60

O6-Methylguanine (m6G) is an altered base produced in DNA by SN1 methylating agents such as N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). This lesion is repaired by the protein O6-methylguanine-DNA methyltransferase (MGMT) in normal human cell lines, but is not repaired in certain human tumor lines that are termed Mex- or Mer-. Compared with repair-proficient cell lines, such repair-deficient tumor lines are hypersensitive to the production by MNNG of sister-chromatid exchanges (SCE), mutations and lethality. We report here that MNNG treatment produces 1 SCE for every 42 +/- 10 m6G formed in the genome of Mer- tumor cells, 1 6TG-resistant mutant for every 8 (range of 5-14) m6G produced statistically in the coding region of the hypoxanthine phosphoribosyltransferase gene, and 1 lethal event per 6650 +/- 1200 m6G. In addition, in vitro base mismatch incision at m6G: BrU pairs was similar to that at m6G: T pairs, the lesions that likely initiate SCE production. We conclude that m6G residues in genomic DNA are very recombinogenic as well as highly mutagenic in Mer- human tumor cells. The results are interpreted in terms of the relationship between methylation-induced SCE and G: T mismatch recognition.
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PMID:On the quantitative relationship between O6-methylguanine residues in genomic DNA and production of sister-chromatid exchanges, mutations and lethal events in a Mer- human tumor cell line. 751 Mar 69

N-Ethyl-N-nitrosourea (ENU) forms several major adducts upon reaction with DNA, of which ethylation at the O6 position of guanine and the O4, O2 and N3 positions of thymine have been implicated to be mutagenic lesions. To investigate what specific kinds of ENU-induced mutations were affected by the repair ability of O6-alkylguanine-DNA alkyltransferase (AGT), we examined the mutations in the hypoxanthine (guanine) phosphoribosyltransferase gene (hprt) in 87 independent mutants derived from ENU-treated AGT proficient (Mer+) or deficient (Mer-) diploid human fibroblasts. Of the characterized mutations, 97% were single base substitutions. The major difference in the mutation spectra was that the frequency of G.C to A.T transitions was significantly higher in Mer- mutants (16/38) than in Mer+ mutants (4/33). The results indicate that AGT removes O6-ethylguanine, thus protecting human cells from parts of the cytotoxic and mutagenic effects of ENU. A high frequency of T.A to A.T transversions induced by ENU was observed in both Mer+ (52%) and Mer- (34%) mutants. This type of mutation was less frequently observed (10%) in N-methyl-N'-nitro-N-nitrosoguanidine (MNNG)-induced mutants derived from the same Mer+ cells in our previous report (J. Mol. Biol., 221, 421, 1991). Comparison of alkylating lesions formed by MNNG and ENU indicates that O2-ethylthymine and N3-ethylthymine are potent mutational adducts for T to A transversions. The occurrence of ENU-induced T.A base pair transversions showed a strong strand bias; 35/37 were located on the non-transcribed strand, assuming thymine is the mutagenic lesion. The result suggests a difference in repair capacity of ethylthymine on the two strands. In addition, this type of mutation preferentially occurred at 5'-Pu-T sequences.
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PMID:Comparison of mutation spectra induced by N-ethyl-N-nitrosourea in the hprt gene of Mer+ and Mer- diploid human fibroblasts. 820 99

In vivo hypoxanthine-guanine phosphoribosyltransferase (HPRT)-deficient T cells (MT) from melanoma patients are enriched for T cells with in vivo clonal amplifications that traffic between blood and tumor tissues. Melanoma is thus a model cancer to test the hypothesis that in vivo MT from cancer patients can be used as immunological probes for immunogenic tumor antigens. MT were obtained by 6-thioguanine (TG) selection of lymphocytes from peripheral blood and tumor tissues, and wild-type T cells (WT) were obtained analogously without TG selection. cDNA sequences of the T cell receptor beta chains (TRB) were used as unambiguous biomarkers of in vivo clonality and as indicators of T cell specificity. Public TRB were identified in MT from the blood and tumor of different melanoma patients. Such public TRB were not found in normal control MT or WT. As an indicator of T cell specificity for melanoma, the >2600 MT and WT TRB, including the public TRB from melanoma patients, were compared to a literature-derived empirical database of >1270 TRB from melanoma-reactive T cells. Various degrees of similarity, ranging from 100% conservation to 3-amino acid motifs (3-mer), were found between both melanoma patient MT and WT TRBs and the empirical database. The frequency of 3-mer and 4-mer TRB matching to the empirical database was significantly higher in MT compared with WT in the tumor (p=0.0285 and p=0.006, respectively). In summary, in vivo MT from melanoma patients contain public TRB as well as T cells with specificity for characterized melanoma antigens. We conclude that in vivo MT merit study as novel probes for uncharacterized immunogenic antigens in melanoma and other malignancies.
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PMID:In vivo 6-thioguanine-resistant T cells from melanoma patients have public TCR and share TCR beta amino acid sequences with melanoma-reactive T cells. 2118 40