Extension of the pre-DNA synthetic phase of the cell cycle as a consequence of DNA alkylation in Chinese hamster cells: A possible mechanism of DNA repair

1971 ◽  
Vol 3 (5) ◽  
pp. 343-351 ◽  
Author(s):  
Janet E. Plant ◽  
J.J. Roberts
Keyword(s):  
Cell Cycle ◽  
Dna Repair ◽  
Chinese Hamster ◽  
Dna Alkylation ◽  
Chinese Hamster Cells ◽  
Synthetic Phase

scholarly journals SYNCHRONIZATION OF MITOCHONDRIAL DNA SYNTHESIS IN CHINESE HAMSTER CELLS (LINE CHO) DEPRIVED OF ISOLEUCINE

1973 ◽  
Vol 58 (2) ◽  
pp. 340-345 ◽  
Author(s):  
Kenneth D. Ley ◽  
Marilyn M. Murphy
Keyword(s):  
Cell Cycle ◽  
Mitochondrial Dna ◽  
Dna Synthesis ◽  
Cell Cycle Progression ◽  
Time Course ◽  
Nuclear Dna ◽  
Tritiated Thymidine ◽  
Chinese Hamster ◽  
Chinese Hamster Cells ◽  
In Cells

Mitochondrial DNA (mit-DNA) synthesis was compared in suspension cultures of Chinese hamster cells (line CHO) whose cell cycle events had been synchronized by isoleucine deprivation or mitotic selection. At hourly intervals during cell cycle progression, synchronized cells were exposed to tritiated thymidine ([3H]TdR), homogenized, and nuclei and mitochondria isolated by differential centrifugation. Mit-DNA and nuclear DNA were isolated and incorporation of radioisotope measured as counts per minute ([3H]TdR) per microgram DNA. Mit-DNA synthesis in cells synchronized by mitotic selection began after 4 h and continued for approximately 9 h. This time-course pattern resembled that of nuclear DNA synthesis. In contrast, mit-DNA synthesis in cells synchronized by isoleucine deprivation did not begin until 9–12 h after addition of isoleucine and virtually all [3H]TdR was incorporated during a 3-h interval. We have concluded from these results that mit-DNA synthesis is inhibited in CHO cells which are arrested in G1 because of isoleucine deprivation and that addition of isoleucine stimulates synchronous synthesis of mit-DNA. We believe this method of synchronizing mit-DNA synthesis may be of value in studies of factors which regulate synthesis of mit-DNA.

Radiosensitization with 5-Bromodeoxyuridine of Chinese Hamster Cells X-Irradiated during Different Phases of the Cell Cycle

1971 ◽  
Vol 47 (3) ◽  
pp. 672 ◽  
Author(s):  
W. C. Dewey ◽  
L. E. Stone ◽  
H. H. Miller ◽  
R. E. Giblak
Keyword(s):  
Cell Cycle ◽  
Chinese Hamster ◽  
Chinese Hamster Cells

scholarly journals REGULATION OF INITIATION OF DNA SYNTHESIS IN CHINESE HAMSTER CELLS

1970 ◽  
Vol 47 (2) ◽  
pp. 453-459 ◽  
Author(s):  
K. D. Ley ◽  
R. A. Tobey
Keyword(s):  
Cell Cycle ◽  
Amino Acids ◽  
Dna Synthesis ◽  
Chinese Hamster ◽  
High Cell ◽  
Chinese Hamster Cells ◽  
Rapid Production ◽  
Cell Concentrations ◽  
G1 Cells ◽  
Growing Population

Suspension cultures of Chinese hamster cells (line CHO), which had stopped dividing and were arrested in G1 following growth to high cell concentrations in F-10 medium, could be induced to reinitiate DNA synthesis and to divide in synchrony upon addition of the appropriate amounts of isoleucine and glutamine. Both amino acids were required to initiate resumption of cell-cycle traverse. Deficiencies in other amino acids contained in F-10 medium did not result in accumulation of cells in G1, indicating a specific action produced by limiting quantities of isoleucine and glutamine. In the presence of sufficient glutamine, approximately 2 x 10-6 M isoleucine was required for all cells to initiate DNA synthesis in a population initially containing 1.5 x 105 cells/ml. Under similar conditions, about 4 x 10-6 M isoleucine was required for all G1-arrested cells to progress through cell division. In contrast, 1 x 10-4 M glutamine was necessary for maximum initiation of DNA synthesis in G1 cells, along with sufficient isoleucine. A technique for rapid production of G1-arrested cells is described in which cells from an exponentially growing population placed in F-10 medium deficient in both isoleucine and glutamine or isoleucine alone accumulated in G1 after 30 hr.

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