Investigation of micronucleus induction in MTH1 knockdown cells exposed to UVA, UVB or UVC. 2015

Asal Fotouhi, and Nicola Cornella, and Mehrafarin Ramezani, and Andrzej Wojcik, and Siamak Haghdoost
Center for Radiation Protection Research, Department of Molecular Biosciences, Wenner-Gren Institute, Stockholm University, Sweden.

The longer wave parts of UVR can increase the production of reactive oxygen species (ROS) which can oxidize nucleotides in the DNA or in the nucleotide pool leading to mutations. Oxidized bases in the DNA are repaired mainly by the DNA base excision repair system and incorporation of oxidized nucleotides into newly synthesized DNA can be prevented by the enzyme MTH1. Here we hypothesize that the formation of several oxidized base damages (from pool and DNA) in close proximity, would cause a high number of base excision repair events, leading to DNA double strand breaks (DSB) and therefore giving rise to cytogenetic damage. If this hypothesis is true, cells with low levels of MTH1 will show higher cytogenetic damage after the longer wave parts of UVR. We analyzed micronuclei induction (MN) as an endpoint for cytogenetic damage in the human lymphoblastoid cell line, TK6, with a normal and a reduced level of MTH1 exposed to UVR. The results indicate a higher level of micronuclei at all incubation times after exposure to the longer wave parts of UVR. There is no significant difference between wildtype and MTH1-knockdown TK6 cells, indicating that MTH1 has no protective role in UVR-induced cytogenetic damage. This indicates that DSBs induced by UV arise from damage forms by direct interaction of UV or ROS with the DNA rather than through oxidation of dNTP.

UI MeSH Term Description Entries
D010744 Phosphoric Monoester Hydrolases A group of hydrolases which catalyze the hydrolysis of monophosphoric esters with the production of one mole of orthophosphate. Phosphatase,Phosphatases,Phosphohydrolase,Phosphohydrolases,Phosphomonoesterase,Phosphomonoesterases,Phosphoric Monoester Hydrolase,Hydrolase, Phosphoric Monoester,Hydrolases, Phosphoric Monoester,Monoester Hydrolase, Phosphoric
D002460 Cell Line Established cell cultures that have the potential to propagate indefinitely. Cell Lines,Line, Cell,Lines, Cell
D004260 DNA Repair The removal of DNA LESIONS and/or restoration of intact DNA strands without BASE PAIR MISMATCHES, intrastrand or interstrand crosslinks, or discontinuities in the DNA sugar-phosphate backbones. DNA Damage Response
D006801 Humans Members of the species Homo sapiens. Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D014466 Ultraviolet Rays That portion of the electromagnetic spectrum immediately below the visible range and extending into the x-ray frequencies. The longer wavelengths (near-UV or biotic or vital rays) are necessary for the endogenous synthesis of vitamin D and are also called antirachitic rays; the shorter, ionizing wavelengths (far-UV or abiotic or extravital rays) are viricidal, bactericidal, mutagenic, and carcinogenic and are used as disinfectants. Actinic Rays,Black Light, Ultraviolet,UV Light,UV Radiation,Ultra-Violet Rays,Ultraviolet Light,Ultraviolet Radiation,Actinic Ray,Light, UV,Light, Ultraviolet,Radiation, UV,Radiation, Ultraviolet,Ray, Actinic,Ray, Ultra-Violet,Ray, Ultraviolet,Ultra Violet Rays,Ultra-Violet Ray,Ultraviolet Black Light,Ultraviolet Black Lights,Ultraviolet Radiations,Ultraviolet Ray
D015162 Micronucleus Tests Induction and quantitative measurement of chromosomal damage leading to the formation of micronuclei (MICRONUCLEI, CHROMOSOME-DEFECTIVE) in cells which have been exposed to genotoxic agents or IONIZING RADIATION. Micronucleus Assays,Assay, Micronucleus,Assays, Micronucleus,Micronucleus Assay,Micronucleus Test,Test, Micronucleus,Tests, Micronucleus
D045643 DNA Repair Enzymes Enzymes that are involved in the reconstruction of a continuous two-stranded DNA molecule without mismatch from a molecule, which contained damaged regions. DNA Repair Enzyme,Enzyme, DNA Repair,Enzymes, DNA Repair,Repair Enzyme, DNA,Repair Enzymes, DNA
D048629 Micronuclei, Chromosome-Defective Defective nuclei produced during the TELOPHASE of MITOSIS or MEIOSIS by lagging CHROMOSOMES or chromosome fragments derived from spontaneous or experimentally induced chromosomal structural changes. Chromosome-Defective Micronuclei,Genotoxicant-Induced Micronuclei,Micronuclei, Genotoxicant-Induced,Micronucleus, Chromosome-Defective,Chromosome Defective Micronuclei,Chromosome-Defective Micronucleus,Genotoxicant Induced Micronuclei,Genotoxicant-Induced Micronucleus,Micronuclei, Chromosome Defective,Micronuclei, Genotoxicant Induced,Micronucleus, Chromosome Defective,Micronucleus, Genotoxicant-Induced
D053903 DNA Breaks, Double-Stranded Interruptions in the sugar-phosphate backbone of DNA, across both strands adjacently. Double-Stranded DNA Breaks,Double-Strand DNA Breaks,Double-Stranded DNA Break,Break, Double-Strand DNA,Break, Double-Stranded DNA,Breaks, Double-Strand DNA,Breaks, Double-Stranded DNA,DNA Break, Double-Strand,DNA Break, Double-Stranded,DNA Breaks, Double Stranded,DNA Breaks, Double-Strand,Double Strand DNA Breaks,Double Stranded DNA Break,Double Stranded DNA Breaks,Double-Strand DNA Break
D055785 Gene Knockdown Techniques The artificial induction of GENE SILENCING by the use of RNA INTERFERENCE to reduce the expression of a specific gene. It includes the use of DOUBLE-STRANDED RNA, such as SMALL INTERFERING RNA and RNA containing HAIRPIN LOOP SEQUENCE, and ANTI-SENSE OLIGONUCLEOTIDES. Gene Knock Down Techniques,Gene Knock Down,Gene Knock-Down,Gene Knock-Down Techniques,Gene Knockdown,Gene Knock Downs,Gene Knock-Down Technique,Gene Knock-Downs,Gene Knockdown Technique,Gene Knockdowns,Knock Down, Gene,Knock Downs, Gene,Knock-Down Technique, Gene,Knock-Down Techniques, Gene,Knock-Down, Gene,Knock-Downs, Gene,Knockdown Technique, Gene,Knockdown Techniques, Gene,Knockdown, Gene,Knockdowns, Gene,Technique, Gene Knock-Down,Technique, Gene Knockdown,Techniques, Gene Knock-Down,Techniques, Gene Knockdown

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