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Carcinogens stimulate intrachromosomal homologous recombination at an endogenous locus in human diploid fibroblasts. 1997

J Li, and R Ayyadevera, and R J Shmookler Reis
Department of Pharmacology and Toxicology, University of Arkansas for Medical Sciences, Little Rock 72205, USA.

Mitotic recombination is believed to play an important role in the development of many cancers. An improved system has been developed to detect reversion of an intragenic DNA duplication, as a model for intrachromosomal homologous recombination. The 'LNtd' strain of human fibroblasts, derived from a Lesch-Nyhan donor, produces no detectable hypoxanthine phosphoribosyltransferase (HPRT) activity due to a 13.7-kilobase-pair DNA insertion duplicating exons 2 and 3 of the HPRT locus. These cells are therefore sensitive to selection in HAT medium, against cells lacking functional HPRT enzyme. Clonal reversion to HAT resistance occurs spontaneously at 1-3 x 10(-5)/cell/generation, and can be induced by brief exposure to a variety of carcinogenic agents. Six known carcinogens, including two (diethylstilbestrol and nickel chloride) which were non-mutagenic in Salmonella by Ames HIS-reversion tests, showed dose-dependent induction of LNtd reversion by a maximum of 2.4- to > 11-fold over controls (each p < 0.01). In contrast, 5 non-carcinogenic agents, including two 'Ames-positive' chemicals, sodium azide and 8-hydroxyquinoline, evoked no more than a 1.7-fold increase in reversion (not significant). The molecular events associated with reversion to HAT-resistance were characterized, relative to the parental strain, in HATR clones derived from either untreated or carcinogen-treated cells. Both the intron-3:intron-1 junction situated between the duplicated HPRT segments in LNtd cells (amplified by polymerase chain reaction), and a restriction fragment corresponding to the duplicated HPRT DNA (assessed by Southern-blot hybridization), were lost from the majority of HATR revertant clones, whether they arose spontaneously or following exposure to Cr(VI) or ultraviolet light. These results imply that HATR reversion is induced in LNtd cells by carcinogenic treatments, through a mechanism consistent with homologous recombination, and is highly concordant with induction of in vivo carcinogenesis by the same agents.

UI MeSH Term Description Entries
D007041 Hypoxanthine Phosphoribosyltransferase An enzyme that catalyzes the conversion of 5-phosphoribosyl-1-pyrophosphate and hypoxanthine, guanine, or MERCAPTOPURINE to the corresponding 5'-mononucleotides and pyrophosphate. The enzyme is important in purine biosynthesis as well as central nervous system functions. Complete lack of enzyme activity is associated with the LESCH-NYHAN SYNDROME, while partial deficiency results in overproduction of uric acid. EC 2.4.2.8. Guanine Phosphoribosyltransferase,HPRT,Hypoxanthine-Guanine Phosphoribosyltransferase,IMP Pyrophosphorylase,HGPRT,HPRTase,Hypoxanthine Guanine Phosphoribosyltransferase,Phosphoribosyltransferase, Guanine,Phosphoribosyltransferase, Hypoxanthine,Phosphoribosyltransferase, Hypoxanthine-Guanine,Pyrophosphorylase, IMP
D007926 Lesch-Nyhan Syndrome An inherited disorder transmitted as a sex-linked trait and caused by a deficiency of an enzyme of purine metabolism; HYPOXANTHINE PHOSPHORIBOSYLTRANSFERASE. Affected individuals are normal in the first year of life and then develop psychomotor retardation, extrapyramidal movement disorders, progressive spasticity, and seizures. Self-destructive behaviors such as biting of fingers and lips are seen frequently. Intellectual impairment may also occur but is typically not severe. Elevation of uric acid in the serum leads to the development of renal calculi and gouty arthritis. (Menkes, Textbook of Child Neurology, 5th ed, pp127) Choreoathetosis Self-Mutilation Hyperuricemia Syndrome,Hypoxanthine-Phosphoribosyl-Transferase Deficiency Disease,Choreoathetosis Self-Mutilation Syndrome,Complete HGPRT Deficiency Disease,Complete HPRT Deficiency,Complete Hypoxanthine-Guanine Phosphoribosyltransferase Deficiency,Deficiency Disease, Complete HGPRT,Deficiency Disease, Hypoxanthine-Phosphoribosyl-Transferase,Deficiency of Guanine Phosphoribosyltransferase,Deficiency of Hypoxanthine Phosphoribosyltransferase,HGPRT Deficiency,HGPRT Deficiency Disease, Complete,Hypoxanthine Guanine Phosphoribosyltransferase 1 Deficiency,Hypoxanthine Guanine Phosphoribosyltransferase Deficiency,Hypoxanthine Phosphoribosyltransferase Deficiency,Juvenile Gout, Choreoathetosis, Mental Retardation Syndrome,Juvenile Hyperuricemia Syndrome,Lesch-Nyhan Disease,Primary Hyperuricemia Syndrome,Total HPRT Deficiency,Total Hypoxanthine-Guanine Phosphoribosyl Transferase Deficiency,X-Linked Hyperuricemia,X-Linked Primary Hyperuricemia,Choreoathetosis Self Mutilation Hyperuricemia Syndrome,Choreoathetosis Self Mutilation Syndrome,Choreoathetosis Self-Mutilation Syndromes,Complete HPRT Deficiencies,Complete Hypoxanthine Guanine Phosphoribosyltransferase Deficiency,Deficiencies, Complete HPRT,Deficiencies, HGPRT,Deficiencies, Hypoxanthine Phosphoribosyltransferase,Deficiencies, Total HPRT,Deficiency Disease, Hypoxanthine Phosphoribosyl Transferase,Deficiency Diseases, Hypoxanthine-Phosphoribosyl-Transferase,Deficiency, Complete HPRT,Deficiency, HGPRT,Deficiency, Hypoxanthine Phosphoribosyltransferase,Deficiency, Total HPRT,Guanine Phosphoribosyltransferase Deficiencies,Guanine Phosphoribosyltransferase Deficiency,HGPRT Deficiencies,HPRT Deficiencies, Complete,HPRT Deficiencies, Total,HPRT Deficiency, Complete,HPRT Deficiency, Total,Hyperuricemia Syndrome, Juvenile,Hyperuricemia Syndrome, Primary,Hyperuricemia Syndromes, Juvenile,Hyperuricemia Syndromes, Primary,Hyperuricemia, X-Linked,Hyperuricemia, X-Linked Primary,Hyperuricemias, X-Linked,Hyperuricemias, X-Linked Primary,Hypoxanthine Phosphoribosyl Transferase Deficiency Disease,Hypoxanthine Phosphoribosyltransferase Deficiencies,Hypoxanthine-Phosphoribosyl-Transferase Deficiency Diseases,Juvenile Hyperuricemia Syndromes,Lesch Nyhan Disease,Lesch Nyhan Syndrome,Phosphoribosyltransferase Deficiencies, Guanine,Phosphoribosyltransferase Deficiencies, Hypoxanthine,Phosphoribosyltransferase Deficiency, Guanine,Phosphoribosyltransferase Deficiency, Hypoxanthine,Primary Hyperuricemia Syndromes,Primary Hyperuricemia, X-Linked,Primary Hyperuricemias, X-Linked,Self-Mutilation Syndrome, Choreoathetosis,Self-Mutilation Syndromes, Choreoathetosis,Syndrome, Choreoathetosis Self-Mutilation,Syndrome, Juvenile Hyperuricemia,Syndrome, Primary Hyperuricemia,Syndromes, Choreoathetosis Self-Mutilation,Syndromes, Juvenile Hyperuricemia,Syndromes, Primary Hyperuricemia,Total HPRT Deficiencies,Total Hypoxanthine Guanine Phosphoribosyl Transferase Deficiency,X Linked Hyperuricemia,X Linked Primary Hyperuricemia,X-Linked Hyperuricemias,X-Linked Primary Hyperuricemias
D009152 Mutagenicity Tests Tests of chemical substances and physical agents for mutagenic potential. They include microbial, insect, mammalian cell, and whole animal tests. Genetic Toxicity Tests,Genotoxicity Tests,Mutagen Screening,Tests, Genetic Toxicity,Toxicity Tests, Genetic,Genetic Toxicity Test,Genotoxicity Test,Mutagen Screenings,Mutagenicity Test,Screening, Mutagen,Screenings, Mutagen,Test, Genotoxicity,Tests, Genotoxicity,Toxicity Test, Genetic
D011995 Recombination, Genetic Production of new arrangements of DNA by various mechanisms such as assortment and segregation, CROSSING OVER; GENE CONVERSION; GENETIC TRANSFORMATION; GENETIC CONJUGATION; GENETIC TRANSDUCTION; or mixed infection of viruses. Genetic Recombination,Recombination,Genetic Recombinations,Recombinations,Recombinations, Genetic
D012150 Polymorphism, Restriction Fragment Length Variation occurring within a species in the presence or length of DNA fragment generated by a specific endonuclease at a specific site in the genome. Such variations are generated by mutations that create or abolish recognition sites for these enzymes or change the length of the fragment. RFLP,Restriction Fragment Length Polymorphism,RFLPs,Restriction Fragment Length Polymorphisms
D002273 Carcinogens Substances that increase the risk of NEOPLASMS in humans or animals. Both genotoxic chemicals, which affect DNA directly, and nongenotoxic chemicals, which induce neoplasms by other mechanism, are included. Carcinogen,Oncogen,Oncogens,Tumor Initiator,Tumor Initiators,Tumor Promoter,Tumor Promoters,Initiator, Tumor,Initiators, Tumor,Promoter, Tumor,Promoters, Tumor
D002478 Cells, Cultured Cells propagated in vitro in special media conducive to their growth. Cultured cells are used to study developmental, morphologic, metabolic, physiologic, and genetic processes, among others. Cultured Cells,Cell, Cultured,Cultured Cell
D002874 Chromosome Mapping Any method used for determining the location of and relative distances between genes on a chromosome. Gene Mapping,Linkage Mapping,Genome Mapping,Chromosome Mappings,Gene Mappings,Genome Mappings,Linkage Mappings,Mapping, Chromosome,Mapping, Gene,Mapping, Genome,Mapping, Linkage,Mappings, Chromosome,Mappings, Gene,Mappings, Genome,Mappings, Linkage
D002999 Clone Cells A group of genetically identical cells all descended from a single common ancestral cell by mitosis in eukaryotes or by binary fission in prokaryotes. Clone cells also include populations of recombinant DNA molecules all carrying the same inserted sequence. (From King & Stansfield, Dictionary of Genetics, 4th ed) Clones,Cell, Clone,Cells, Clone,Clone,Clone Cell
D003470 Culture Media Any liquid or solid preparation made specifically for the growth, storage, or transport of microorganisms or other types of cells. The variety of media that exist allow for the culturing of specific microorganisms and cell types, such as differential media, selective media, test media, and defined media. Solid media consist of liquid media that have been solidified with an agent such as AGAR or GELATIN. Media, Culture

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