The Direct Effect of X-Irradiation on HeLa S3 Deoxyribonucleic Acid Synthesis

Journal Article · Fri Jun 01 04:00:00 EDT 1962 · Radiation Research

DOI:https://doi.org/10.2307/3571283· OSTI ID:4838043

Painter, Robert B.

In HeLa S3 cell cultures, after x irradiation, there is an immediate depression of the rate of DNA synthesis, as measured by the incorporation of labeled nucleosides into the nucleic acids. There is no similar depression in RNA synthesis or incorperation of the tracer into the soluble pool, so that phosphorylation reactions do not seem to be the radiation-affected site. The extent of the inhibition of rate of DNA synthesis is dose-dependent, and the doseresponse curve appears to be a two-component one. A tentative hypothesis has been made that the steeper (radiosensitive) component is due to an effect on primer, predominantly of cells in DNA synthesis at the time of irradiation, and the less steep (radioresistant) component is due to an effect on the polymerase- forming system, predominantly of cells in the pre-DNA synthesis (G/sub 1/) phase during irradiation. The effect of radiation on suppression of rate of DNA synthesis varies to a considerable extent from experiment to experiment and to a lesser extent from culture to culture. The basis of this variability is unknown but appears to depend to a great extent on the DNA metabolic activity df the individual cultures at the time of irradiation. Rapidly synthesizing cultures are most inhibited by irradiation, but very poorly metabolizing ones also contribute to the variability, simply because of their initial slower rate of DNA synthesis. Good correlation between specificactivity results and grain-count results has been obtained, but only by using the average values of grain counts over several control and irradiated cultures, because of the large variation among individual cultures. The immediate effect on the rate of DNA synthesis is great enough to explain our previous observations of increased percentages of cells in DNA synthesis (S retention) after 500 r of irradiation. Since the cells require a longer time to accomplish chromosomal replication, but the rate of entry of cells from Gi into the DNA synthesis phase is undimin ished, a pile-up of cells in DNA synthesis phase results. (auth)

• Research Organization: Battelle Memorial Inst., Columbus, Ohio
• Sponsoring Organization: USDOE
• NSA Number: NSA-16-021974
• OSTI ID: 4838043
• Journal Information: Radiation Research, Journal Name: Radiation Research Journal Issue: 6 Vol. 16; ISSN 0033-7587
• Publisher: Radiation Research Society
• Country of Publication: Country unknown/Code not available
• Language: English

Related Subjects

ANIMAL CELLS
BIOCHEMISTRY
BIOLOGY AND MEDICINE
CHROMOSOMES
CYTOLOGY
MITOSIS
NUCLEIC ACIDS
QUANTITY RATIO
RADIATION DOSES
RADIATION EFFECTS
RADIOSENSITIVITY
TRACER TECHNIQUES
X RADIATION