DNA replication and the repair of DNA strand breaks in nuclei of Physarum polycephalum. Progress report, September 1, 1977--July 31, 1978. [Monel]

Technical Report · Tue Aug 01 04:00:00 EDT 1978

DOI:https://doi.org/10.2172/6452608· OSTI ID:6452608

Brewer, E N; Nygaard, O F; Kuncio, G

Isolated nuclei and intact plasmodia of Physarum contain a heat-stable stimulator of nuclear DNA replication. This substance has been purified extensively and found to contain both protein and carbohydrate. The molecular weight, estimated by gel filtration, is ca. 30,000 d. The purified material does not exhibit DNA polymerase or DNase activity, and does not stimulate DNA polymerase activity per se. In the presence of the stimulatory factor, DNA chain elongation occurs at an elevated rate, and continues for a longer time than in its absence, but G/sub 2/ nuclei are not stimulated to initiate DNA synthesis. Double-strand breaks in nuclear DNA of irradiated plasmodia are repaired in vitro to a greater extent following nuclear isolation during G/sub 2/, and the DNA of unirradiated plasmodia is less susceptible to double-strand breakage during cell-free nuclear incubation, than is the DNA of S-phase nuclei. This correlation suggests a common basis for both observations, for example an increase in deoxyribonuclease activity or a decrease in DNA ligase activity during the S period. This, in turn, may account for the cell cycle-dependent sensitivity of this organism, in terms of mitotic delay, to ionizing radiation.

• Research Organization: Case Western Reserve Univ., Cleveland, OH (USA). Div. of Radiation Biology
• OSTI ID: 6452608
• Report Number(s): COO-2486-369
• Country of Publication: United States
• Language: English

Related Subjects

550200 -- Biochemistry
560131* -- Radiation Effects on Microorganisms-- Basic Studies-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOCHEMICAL REACTION KINETICS
BIOLOGICAL EFFECTS
BIOLOGICAL RADIATION EFFECTS
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
CELL CONSTITUENTS
CELL DIVISION
CELL NUCLEI
DNA
DNA REPLICATION
FUNGI
IONIZING RADIATIONS
KINETICS
MOLECULAR BIOLOGY
MYXOMYCETES
NUCLEIC ACID REPLICATION
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PLANTS
RADIATION EFFECTS
RADIATIONS
RADIOSENSITIVITY
REACTION KINETICS
RECOVERY
REPAIR
RESPONSE MODIFYING FACTORS
STRAND BREAKS