Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.4.2.7 (adenine phosphoribosyltransferase)
 692 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We investigated the specific sequence changes produced by the dietary mutagen 2-amino-1-methyl-6-phenylimidazo-[4,5-b]pyridine (PhIP) in UV5P3 cells [a Chinese hamster ovary (CHO) cell line]. Sequence analysis of the PhIP-induced mutations in the adenine phosphoribosyltransferase (aprt) gene, which is heterozygous in the UV5P3 cells, can provide insight into the mutagenic mechanism in these repair-deficient cells expressing P4501A2. Two allele-specific 20 mer oligonucleotide primer pairs were used in the polymerase chain reaction and the allele of interest was amplified. Single-base transversions occurred in 31/32 PhIP-induced mutants; of these, 6 were A.T-->T.A, 18 were C.G-->A.T and 6 were G.C-->T.A. Twenty of the 30 changes altered specific amino acid sequences and the other 10 resulted in a stop codon. On mutant had a change from C.G-->G.C at the 3' splice site of intron 4, thereby creating a new AG splice acceptor site. Another mutant had an insertion of T within a run of repeated sequences and resulted in a frameshift mutation. There were three 'hot-spots', two at the 3' end of exon 2 and one at the beginning of exon 3; 6 (19%) mutants showed a change from A.T-->T.A (exon 2, amino acid residue 57), 11 (34%) mutants from C.G-->A.T (exon 2, amino acid residue 62), and 7 (22%) mutants from C.G-->A.T (exon 3, amino acid residue 66). Consequently, 75% of the mutations were observed at these three sites. In contrast, none of the 20 spontaneous mutants had alterations at these hotspot sites. The mutations induced by PhIP in these repair-deficient CHO cells were unique and specific, and suggest that these sequences, if found in important genes controlling cell replication and survival, may be more susceptible to mutation from these food mutagens than genes not containing these sequences.
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PMID:Identification of aprt gene mutations induced in repair-deficient and P450-expressing CHO cells by the food-related mutagen/carcinogen, PhIP. 776 87

High-density mutational spectra have been established for exon 3 of the gene encoding adenine phosphoribosyltransferase (APRT) of the Chinese hamster ovary (CHO) cell line derivative D422 and closely related and/or modified lines by using the mutagen ethyl methanesulfonate (EMS). The total number of selectable sites (GC-->AT transitions yielding a selectable APRT- phenotype) was estimated at 31 based on our own accumulated data base of 136 sequenced exon 3 mutations and on literature reports. D422 and two other APRT hemizygous lines each yielded very similar spectra and showed two populations of mutable sites: (i) 24 "baseline" sites that followed the Poisson distribution and therefore were equally susceptible to mutation and (ii) two hotspots, one comprising a cluster at nucleotides 1293-1309 and the other at nucleotide 1365. Collectively, the latter sites were about 10-fold more frequently mutated than the others. CHO cells are mer- as they lack the repair enzyme O6-methylguanidine methyltransferase (EC 2.1.1.63). In modified repair-proficient CHO cells, the distribution of mutations among all of the 31 sites was random, with only 3 of the 19 GC-->AT transitions in the above hotspots. To determine whether the distribution was locus-dependent, two independent lines carrying single copies of transfected APRT genes were generated from a derivative of D422 carrying a deletion in the endogenous APRT gene. Nucleotides 1293-1309 were again no longer preferentially mutated, but the site at nucleotide 1365 was still a hotspot. We conclude that mutational spectra in mer- cells are at least in part locus dependent and that some sequences are particularly susceptible to EMS mutagenesis and perhaps also to methyltransferase repair.
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PMID:Influence of alkyltransferase activity and chromosomal locus on mutational hotspots in Chinese hamster ovary cells. 855 87