Role of DNA damage and repair in the function of eukaryotic genes: radiation-induced single-strand breaks and their rejoining in chromosomal and extrachromosomal ribosomal DNA of Tetrahymena
The production and rejoining of single-strand breaks (SSB) in chromosomal DNA and extrachromosomal ribosomal DNA (rDNA) were investigated after sublethal doses of ..gamma.. radiation to exponentially growing Tetrahymena. Hydrogen-3-labeled total nuclear DNA isolated from either control or irradiated cells was heat denatured and electrophoresed in agarose gels containing formaldehyde. Ribosomal DNA was identified by hybridization to (/sup 32/P)rRNA after transferring the DNA from the gels to nitrocellulose strips. It was found that (a) approximately 0.68 SSB is produced in each strand of rDNA exposed to 40 krad; (b) greater than 80% of SSB were rejoined within the first 20 min after irradiation in both chromosomal and rDNA; and (c) the rejoining process in both chromosomal and rDNA proceeded in the presence of inhibitors of protein synthesis, RNA synthesis, or oxidative metabolism. While the majority of SSB induced by 40 krad is rejoined within 20 min after irradiation, the resumption of rRNA synthesis does not occur until 30 min thereafter; it is concluded that the restoration of the normal size of the rDNA template is probably necessary but not sufficient for the resumption of rRNA synthesis.
- Research Organization:
- Case Western Reserve Univ., Cleveland, OH
- OSTI ID:
- 5023393
- Journal Information:
- Radiat. Res.; (United States), Vol. 82:1
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
59 BASIC BIOLOGICAL SCIENCES
DNA
BIOLOGICAL RADIATION EFFECTS
GENES
RNA
STRAND BREAKS
RADIOINDUCTION
BIOLOGICAL REPAIR
DOSE-RESPONSE RELATIONSHIPS
EXPERIMENTAL DATA
GAMMA RADIATION
LABELLED COMPOUNDS
PHOSPHORUS 32
RIBOSOMES
SUBLETHAL IRRADIATION
TETRAHYMENA
TIME DEPENDENCE
TRITIUM
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOLOGICAL EFFECTS
BIOLOGICAL RECOVERY
CELL CONSTITUENTS
DATA
DAYS LIVING RADIOISOTOPES
ELECTROMAGNETIC RADIATION
HYDROGEN ISOTOPES
INFORMATION
INVERTEBRATES
IONIZING RADIATIONS
IRRADIATION
ISOTOPES
LIGHT NUCLEI
MICROORGANISMS
NUCLEI
NUCLEIC ACIDS
NUMERICAL DATA
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC COMPOUNDS
ORGANOIDS
PHOSPHORUS ISOTOPES
PROTOZOA
RADIATION EFFECTS
RADIATIONS
RADIOISOTOPES
RECOVERY
REPAIR
YEARS LIVING RADIOISOTOPES
560112* - Radiation Effects on Biochemicals- In Microorganisms- (-1987)
560131 - Radiation Effects on Microorganisms- Basic Studies- (-1987)
550401 - Genetics- Tracer Techniques