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)

A mouse adenine phosphoribosyltransferase (aprt) pseudogene that had previously been recovered from a BALB/c sperm DNA library possessed several unusual features. Its nucleotide sequence, like that of other processed pseudogenes, was colinear with its corresponding mRNA, but it was truncated at its 3' end and lacked a poly(A) tail. The pseudogene was 82% homologous with corresponding regions of the functional gene and had incurred mutations that included transitions, transversions, deletions, and a point insertion. Even though the pseudogene was truncated within the protein-coding region of the corresponding functional gene, it was flanked at both ends by 13-base-pair direct repeats. Curiously, the direct repeats exhibited homology to APRT mRNA at the site of pseudogene divergence. The pseudogene appeared to be common to BALB/c and A/J mice, but it was contained on a 3-kilobase EcoRI fragment in the former strain and a 4.5-kilobase EcoRI fragment in the latter. The BALB/c and apparently the A/J pseudogene both mapped to chromosome 8, which also contains the functional aprt gene. The DNA sequences immediately surrounding the pseudogene in the two strains appeared to be similar, suggesting that the BALB/c and A/J pseudogenes are allelic. However, DNA sequences more distal to the pseudogene in the two strains appeared to vary. Thus, the EcoRI polymorphism was not due to simple loss of an EcoRI site, but was more complex. The pattern of flanking restriction sites was different for each of several enzymes, consistent with extensive DNA rearrangement. Double digests of BALB/c and A/J genomic DNAs revealed complex polymorphisms on both sides of the pseudogene. The results were consistent with insertion, deletion, or other rearrangement of DNA sequences that flank the pseudogene and suggest that this region of mouse chromosome 8 may be a region active for mutation or recombination.
Mol Cell Biol 1986 Dec
PMID:An unusual adenine phosphoribosyltransferase pseudogene is syntenic with its functional gene and is flanked by highly polymorphic DNAs. 302 40

Six mutations, impairing DNA polymerase of E. coli in combination with the wild type gene for rho factor or ts-mutation rho 15 have been studied in relation to the expression of seven operons having different types of regulation. The expression of genes for glucose-6-phosphate dehydrogenase and 6-phosphogluconate dehydrogenase is shown to be constitutive and resistant to mutationally altered RNA polymerase and rho factor. The expression of genes for adenine phosphoribosyltransferase and of deo operon is regulated by rho dependent attenuators with attenuation being lifted incomplete medium. Mutation rho 15 decreases the level of enzymes of thr and lac operons independent of mRNA levels of these operons. Mutation rho 15 effect on posttranscriptional level is modified by mutations damaging RNA polymerase. The data obtained suppose RNA polymerase to affect all stages of realization of genetic information, beginning with promoter recognition and RNA synthesis and including the protein synthesis on mRNA.
Mol Gen Mikrobiol Virusol 1985 Oct
PMID:[Effect of mutation changes in RNA-polymerase and transcription termination factor rho on expression of various operons in E. coli]. 302 82

To determine the nature of spontaneous mutational events in cellular genes in hamster cells, mutant adenine phosphoribosyltransferase (aprt) genes were cloned and the regions to which we mapped alterations were sequenced. A variety of nucleotide changes were found to occur in the 12 mutant genes analyzed. Most mutations were simple base-pair substitutions-transitions (both G X C----A X T and A X T----G X C) and transversions. The only multiple mutation was a simple transition next to a single-base-pair insertion. Of the 12 mutations, 4 were more complex, involving small deletions or duplications. Two of these were similar to previously described deletions in that they occurred between short direct sequence repeats. No hot spots were detected. Three independent mutations were characterized at one restriction endonuclease site, although no other mutations were detected in the nucleotides surrounding this site in other mutant strains. At a functional level, sequence changes were either in exons (resulting in missense and, in one instance, nonsense mutations) or at splicing sites.
Mol Cell Biol 1987 Apr
PMID:DNA sequence analysis of spontaneous mutations at the aprt locus of hamster cells. 303 19

Pseudodiploid Chinese hamster V79-AP4 cells, functionally diploid at the adenine phosphoribosyltransferase (aprt) locus, were treated with colcemid, a well-known aneuploidizing agent, under various experimental conditions. Aneuploid and tetraploid cells and variants resistant to 10 micrograms/ml of 2,6-diaminopurine (DAP), which selects for presumptive aprt+/- heterozygotes in the untreated cells, were induced. Many of the induced variants were hypotetraploid with three (rather than four) chromosomes carrying the aprt gene. Dot-blot and Southern analysis of the DNA of these clones confirmed that they had three copies of the aprt gene. Their APRT specific enzymatic activity was 60-80% of that of wild-type V79-AP4. The results of these and other experiments suggest that in these variants resistance to DAP is due to an altered aprt gene dosage and point to a possible genetic effect of colcemid and other aneuploidizing agents in somatic mammalian cells.
Somat Cell Mol Genet 1988 Nov
PMID:Gene dosage mutants at adenine phosphoribosyltransferase locus induced by colcemid in Chinese hamster V79-AP4 cells. 305 53

The 5' end of the Chinese hamster ovary aprt gene was sequenced and transcription start sites were determined by both S1 nuclease protection and primer extension assays. Deletion mutants covering the same area were constructed, and adenine phosphoribosyltransferase (APRT) or chloramphenicol acetyltransferase (CAT) activity was measured by transient-expression assays. The aprt gene uses a single cluster of transcription start sites and lacks consensus sequences such as TATA and CCAAT, which are general components of eucaryotic promoters. The 5' deletion mutations of the promoter sequences demonstrated that (i) there is no decrease in either APRT activity or transcription extending to position -89 (relative to the main transcription start site); (ii) an additional 29-base-pair (bp) deletion decreases APRT activity and transcription twofold; and (iii) a deletion past the transcription start sites (P5' delta +27) abolishes both APRT activity and transcription, indicating that a 60-bp fragment immediately upstream of the main transcription start site is involved in basic transcription and a 29-bp fragment just upstream of the 60 bp-fragment stimulates transcription twofold. The 3' deletion mutations showed that a deletion of a 61-bp fragment in the 5' leader and coding sequence abolishes the efficient translation of an aprt-CAT gene transcript. In addition, there are two polyadenylation signals at the genomic 3' end, with the proximal one being sufficient for functional polyadenylation.
Mol Cell Biol 1988 Jun
PMID:Analysis of signals controlling expression of the Chinese hamster ovary aprt gene. 340 12

Isolation of electrophoretic mobility shift mutants for a large number of enzyme loci in CHO cells has allowed the identification of many genes which are functionally hemizygous. To gain further insight into the nature of hemizygosity in CHO cells and the mechanisms by which it has arisen, we are attempting to determine whether hemizygous gene loci are clustered in a few localized chromosomal regions in CHO or are more generally distributed throughout the genome. Isozyme analysis of a series of CHO electrophoretic mobility shift mutants for MDH2 (malate dehydrogenase 2, EC 1.1.1.37) revealed that this locus is functionally hemizygous in CHO cells, but the locus could not be mapped by conventional approaches because of the similar electrophoretic mobilities of Chinese hamster and mouse MDH2 isozymes. Construction of intraspecific CHO X CHO hybrids using electrophoretic mobility shift mutants with secondary, selectable drug-resistance markers allowed us to determine that MDH2 is not closely linked to any previously mapped hemizygous marker loci in CHO, but is linked to alleles for two dizygous gene loci, PGM3 and APRT, on CHO chromosome Z7. A possible genetic basis for hemizygosity of the MDH2 locus in CHO cells is discussed.
Somat Cell Mol Genet 1986 Mar
PMID:Functional hemizygosity for the MDH2 locus in Chinese hamster ovary cells. 345 74

Three multipotent mouse teratocarcinoma stem lines, all exhibiting unstable expression for the purine salvage enzyme adenine phosphoribosyltransferase (APRT) were used for the isolation of differentiated cell lines from neoplasms developed in syngeneic mice. Two of the stem cell lines (DAP1B and DAP1C) exhibited homozygous deficiencies for APRT expression while the third stem cell line (E140) exhibited a heterozygous deficiency (Turker, M.S., Smith, A.C., and Martin, G.M.; Somat. Cell Mol. Genet.; 10:55-69; 1984). A total of 16 morphologically differentiated cell lines were established from these neoplasms; most were no longer tumorigenic. Differentiated cell lines derived from the E140-induced tumors segregated homozygous deficient mutants in a single step, consistent with their retention of the heterozygous deficient state. Differentiated homozygous deficient cell lines gave rise to phenotypic revertants at very high frequencies (10(-1) to 10(-2)). The majority of these putative revertants, however, yielded cell-free extracts with little or no detectable APRT activity. These putative revertants were capable of adenine salvage and were therefore termed APRT pseudorevertants. Since the APRT pseudorevertant phenotype was only observed in the differentiated progeny of the APRT deficient stem cell lines, we conclude that this change in the nature of the revertant phenotype was a consequence of cellular differentiation.
 ...
PMID:Differentiation alters the unstable expression of adenine phosphoribosyltransferase in mouse teratocarcinoma cells. 378 83

Adenine phosphoribosyltransferase (APRT) (EC 2.4.2.7) pseudorevertant cell lines were isolated under selective conditions requiring adenine salvage for survival; yet they were found to be deficient in measurable APRT activity and resistant to the purine analog 2'6'-diaminopurine (DAP) (M.S. Turker, J. A. Tischfield, P. Rabinovitch, P.J. Stambrook, J.J. Trill, A.C. Smith, C.E. Ogburn, and G.M. Martin, manuscript in preparation). Adenine salvage was examined in two APRT pseudorevertant cell lines, their two APRT homozygous deficient parental cell lines, and a genotypic APRT revertant cell line (i.e., one with measurable APRT activity and DAP sensitivity). Adenine accumulation was observed in both revertant phenotypes and was demonstrated by high-performance liquid chromatography to be linked with adenine metabolism. The ability to salvage adenine declined substantially in the pseudorevertant cell lines when they were removed from selective media containing inhibitors of de novo 5'-AMP synthesis (alanosine and azaserine); for one pseudorevertant cell line this decline was accelerated by the addition of DAP to the medium. The readdition of alanosine or azaserine to the growth medium of the pseudorevertant lines induced adenine salvage to its previous levels. An APRT-like cross-reacting material was found in the pseudorevertant cell lines, although its relationship to adenine salvage is unknown. A low level of constitutive adenine salvage was found in the parental APRT-deficient lines, and it was also possible to induce adenine salvage in these cell lines. These findings suggest a novel regulatory mechanism for adenine salvage.
Mol Cell Biol 1985 Oct
PMID:Induction of adenine salvage in mouse cell lines deficient in adenine phosphoribosyltransferase. 383 81

We have investigated the effect of cell cycle position on the efficiency of transformation by microinjection. Linear recombinant plasmids transform synchronized cells with similar frequencies following injections at all cell cycle stages, whereas supercoiled molecules show a decreased ability to generate transformants in early S phase. This inhibition is not due to an inability to transiently express a transferred gene, since cells at all stages of the cycle efficiently expressed a hamster adenine phosphoribosyltransferase gene introduced on a supercoiled plasmid. Southern transfer analyses of the cell cycle specific transformants revealed that tandem arrays of plasmids, integrated into the host chromosomes, could be generated at all cell cycle stages.
Somat Cell Mol Genet 1985 Jan
PMID:Effect of cell cycle position on transformation by microinjection. 385 30

A complete human APRT gene has been isolated from a lambda phage genomic library using cloned mouse APRT DNA as a probe. The human gene, contained in a recombinant lambda phage designated lambda Huap15, is functional by virtue of its capacity to transfer human APRT activity to Aprt- mouse recipient cells after phage-mediated transfection. Digestion of lambda Huap15 DNA with BamH1 generated a 2.2-kb fragment that is the only fragment of eight produced to hybridize with the mouse APRT gene. This 2.2-kb BamH1 fragment is a unique, single copy sequence, and has been used to identify a restriction fragment length polymorphism (RFLP) associated with the APRT locus. Taq1 digestion and Southern blot analysis of DNAs from 49 unrelated individuals produced three different patterns. DNAs of 30 individuals produced a restriction pattern of three labeled fragments about 500 bp, 600 bp, and 2.1 kb in size, which is characteristic for individuals homozygous for the more common allele. Two individuals homozygous for the less frequent allele displayed labeled fragments of 500 bp and 2.7 kb. The remaining 17 DNA samples produced all four labeled bands as expected for heterozygous individuals. The frequency of heterozygotes in the population is about 35%, while the frequency of the less common allele is about 0.21. Restriction enzyme analysis of DNAs from two APRT-deficient brothers and from an unrelated heterozygote revealed no gross deletions or rearrangements, nor the Taq1 polymorphism.
Somat Cell Mol Genet 1984 Jul
PMID:Cloning of a functional human adenine phosphoribosyltransferase (APRT) gene: identification of a restriction fragment length polymorphism and preliminary analysis of DNAs from APRT-deficient families and cell mutants. 608 72


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