DNA methylation in human fibroblasts following DNA damage and repair
Methylation of deoxycytidine (dCyd) incorporated by DNA excision repair synthesis in human diploid fibroblasts following damage with ultraviolet radiation (UV), N-methyl-N-nitrosourea, or N-acetoxy-2-acetylaminofluorene was studied utilizing (6-/sup 3/H)dCyd to label repaired DNA specifically and high performance liquid chromatographic analysis to quantify the percentage of deoxycytidine converted to 5-methyldeoxycytidine (m/sup 5/dCyd). In confluent, nondividing cells, methylation in repair patches induced by all three agents is slow and incomplete. Whereas after DNA replication a level of 3.4% m/sup 5/dCyd is reached in less than 2 hours, following UV-stimulated repair synthesis in confluent cells it takes about 3 days to reach a level of approx.2.0% m/sup 5/dCyd in the repair patch. This undermethylation of repair patches occurs throughout the genome. In cells from cultures in logarithmic-phase growth, m/sup 5/dCyd formation in UV-induced repair patches occurs faster and to a greater extent, reaching a level of approx.2.7% in 10-20 hours. Pre-existing hypomethylated repair patches in confluent cells are methylated further when the cells are stimulated to divide; however, the repair patch may still not be fully methylated before cell division occurs. Thus DNA damage and repair may lead to heritable loss of methylation at some sites. The distribution within chromatin of m/sup 5/dCyd in repair patches was also investigated. Over a wide range of extents of digestion by staphylococcal nuclease or deoxyribonuclease I, the level of hypomethylation in repaired DNA in nuclease sensitive and resistant regions of chromatin was constant relative to the genomic level of methylation in these regions. Similar conclusions were reached in experiments with isolated mononucleosomes.
- Research Organization:
- Washington Univ., St. Louis, MO (USA)
- OSTI ID:
- 6264756
- Resource Relation:
- Other Information: Thesis (Ph. D.)
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
DEOXYCYTIDINE
METHYLATION
FIBROBLASTS
GENETIC RADIATION EFFECTS
FLUORINE
TOXICITY
NITROSOUREAS
CHROMATIN
DNA
DNA REPAIR
DNA REPLICATION
MITOSIS
NUCLEASES
TRACER TECHNIQUES
TRITIUM COMPOUNDS
ULTRAVIOLET RADIATION
ANIMAL CELLS
AZINES
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CELL DIVISION
CHEMICAL REACTIONS
CONNECTIVE TISSUE CELLS
ELECTROMAGNETIC RADIATION
ELEMENTS
ENZYMES
ESTERASES
GENETIC EFFECTS
HALOGENS
HETEROCYCLIC COMPOUNDS
HYDROLASES
ISOTOPE APPLICATIONS
LABELLED COMPOUNDS
NITROSO COMPOUNDS
NONMETALS
NUCLEIC ACID REPLICATION
NUCLEIC ACIDS
NUCLEOSIDES
NUCLEOTIDES
ORGANIC COMPOUNDS
ORGANIC NITROGEN COMPOUNDS
PHOSPHODIESTERASES
PYRIMIDINES
RADIATION EFFECTS
RADIATIONS
RECOVERY
REPAIR
RIBOSIDES
SOMATIC CELLS
560121* - Radiation Effects on Cells- External Source- (-1987)
560306 - Chemicals Metabolism & Toxicology- Man- (-1987)