DNA replication and the repair of DNA strand breaks in nuclei of Physarum polycephalum. Terminal report, August 1, 1978-March 31, 1980

Technical Report · Tue Jan 01 04:00:00 EST 1980

DOI:https://doi.org/10.2172/5277380· OSTI ID:5277380

Brewer, E N; Evans, T E

Nuclei isolated from Physarum are able to replicate approximately 15% of the total genome in a manner which is qualitatively similar to the DNA replication process occurring in the intact organism. Such nuclei, however, are defective in the joining of Okazaki intermediates in vitro. Two DNA polymerase species, isolated from nuclei or intact plasmodia of this organism, can be separated by sucrose density gradient centrifugation. Total DNA polymerase activity is low in nuclei isolated during mitosis. A heat-stable glycoprotein material present in aqueous nuclear extracts stimulates DNA synthesis in well-washed nuclei. A sub-nuclear preparation active in DNA synthesis in vitro has been obtained from isolated nuclei of Physarum. Radiation-induced DNA double-strand breaks are rejoined in intact plasmodia and isolated nuclei of Physarum in a cell cycle-dependent manner. This phenomenon does not appear to be due to an intrinsic difference in nuclear DNA endonuclease activity at different times of the mitotic cycle. DNA strand breaks and repair induced by the carcinogen 4-nitroquinoline-1-oxide is similar in several respects to that resulting from exposure of the organism to ionizing radiation. Temperature sensitive strains of Physarum have been constructed and preliminary genetical and biochemical characterizations have been carried out. Two of the strains appear to be conditionally defective in DNA metabolism. An isogenic ploidal series of amoebae has been prepared and characterized as to uv and ionizing radiation sensitivity (in terms of cell survival). There is a direct relationship between ploidy and resistance to uv whereas ploidal change does not appear to affect the response to ionizing radiation.

• Research Organization: Case Western Reserve Univ., Cleveland, OH (USA). Dept. of Radiology
• DOE Contract Number: AS02-76EV02486
• OSTI ID: 5277380
• Report Number(s): COO-2486-369-1
• Country of Publication: United States
• Language: English

Related Subjects

550300* -- Cytology
560121 -- Radiation Effects on Cells-- External Source-- (-1987)
59 BASIC BIOLOGICAL SCIENCES
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.
BIOLOGICAL RECOVERY
BIOLOGICAL REPAIR
BIOSYNTHESIS
CELL CONSTITUENTS
CELL CULTURES
CELL CYCLE
CELL DIVISION
CELL NUCLEI
DNA
DNA REPLICATION
ENZYMES
FUNGI
MITOSIS
NUCLEIC ACID REPLICATION
NUCLEIC ACIDS
ORGANIC COMPOUNDS
PHYSARUM
PLANTS
POLYMERASES
RADIOINDUCTION
RECOVERY
REPAIR
STRAND BREAKS
SYNTHESIS