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Toxicity and repair of 5-hydroxymethyluracil: A product of oxidative DNA damage

Thesis/Dissertation ·
OSTI ID:5545544

The ({sup 3}H)-labelled deoxyribonucleoside and the nucleotide triphosphate of HmUra were synthesized and enzymatically and chemically characterized. The {sup 3}H-labelled nucleoside was used to demonstrate the in vivo repair of HmUra from the DNA of Chinese hamster cells. The triphosphate was used for the in vitro construction of the DNA of an amber mutant of bacteriophage 0X-174 using DNA polymerase to place an HmUra instead of a thymine at the amber codon. HmUra did not cause point mutations during in vivo replication of this phage DNA construct following transfection into E. coli spheroplasts. HmUra-DNA glycosylase was found in mammalian cells and tissues, but not in yeast or bacteria. In mouse tissue, the activity was highest in brain and thymus. 5-hydroxymethyl-2{prime}-deoxyuridine was incorporated into the DNA of hamster cells, but was only toxic at concentrations which caused substitution of 1 HmUra/3600 Thy. The conclusion drawn from this work and related studies is that HmUra:Ade base pairs rarely lead to mutations. Thus, formation of HmUra via oxidation of thymine was not sufficiently mutagenic to promote the evolutionary development of a repair glycosylase in bacteria or yeast and is minimally deleterious to higher organisms. The toxicity of HmUra in DNA may be related to its formation from oxidation of 5-methylcytosine to 5-hydroxymethylcytosine which then deaminates to HmUra. The ensuing HmUra:Gua mismatch will lead to a point mutation in the absence of repair. The phylogenetic and tissue distribution supports the hypothesis that the glycosylase participates in the control of differentiated gene expression by maintaining 5-methylcytosine sites in DNA.

Research Organization:
New York Univ., NY (United States)
OSTI ID:
5545544
Country of Publication:
United States
Language:
English

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Related Subjects

550201* -- Biochemistry-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
ANIMAL CELLS
ANIMALS
AZINES
BACTERIA
BACTERIOPHAGES
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CHEMICAL COMPOSITION
DNA POLYMERASES
DNA REPAIR
ENZYMES
ESCHERICHIA COLI
GENE REGULATION
GLYCOSYL HYDROLASES
HAMSTERS
HETEROCYCLIC COMPOUNDS
HYDROGEN COMPOUNDS
HYDROLASES
HYDROXY COMPOUNDS
ISOTOPE APPLICATIONS
MAMMALS
MICE
MICROORGANISMS
MUTAGENESIS
NUCLEOTIDES
NUCLEOTIDYLTRANSFERASES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PARASITES
PHOSPHORUS-GROUP TRANSFERASES
POLYMERASES
PYRIMIDINES
RECOVERY
REPAIR
RODENTS
THYMINE
TRACER TECHNIQUES
TRANSFERASES
TRITIUM COMPOUNDS
URACILS
VERTEBRATES
VIRUSES