Synchronization of DNA synthesis in Tetrahymena populations by temporary limitation of access to thymine compounds

Villadsen, I S; Zeuthen, Erik

doi:10.1016/0014-4827(70)90452-0

Cited by 33 publications

(14 citation statements)

References 15 publications

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“…1 A, curve 2). These results support the previous suggestion that M + U affects DNA metabolism by producing a nutritional deficiency for thymidine (34,38). Furthermore, DNA synthesis can be effectively inhibited, for a period of 4 hr, with a lower concentration of uridine than employed in the recent investigations of Zeuthen and coworkers (34,39).…”

Section: Extent and Specificity Of Inhibition Of Dna Synthesissupporting

confidence: 90%

“…1 B, curve 1). The slight effect of the inhibitor on protein syn~ thesis is probably mediated through effects on RNA synthesis (34). Thus, although IvI + U is a rapid and potent inhibitor of DNA synthesis, at the concentrations used in this study it also has a moderate effect on protein synthesis.…”

Section: Extent and Specificity Of Inhibition Of Dna Synthesismentioning

confidence: 63%

“…In all experiments methotrexate and uridine (iV[ + U) were employed at 0 05 m~t and 5.0 rn~, respectively, the concentrations originally used by Zeuthen (38). The higher concentradous employed in the more recent investigations of Zeuthen and coworkers (34,39) always led to lysis of cells cultured in microdrops Protein synthesis was inhibited with eycloheximide (actidione, ICN Nutritional Biochemicals Div, International Chemical and Nuclear Corp, Cleveland, Ohio) at a concentration of ~g/mi OiL…”

Section: General Proceduresmentioning

confidence: 99%

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EVIDENCE FOR A TEMPORAL INCOMPATIBILITY BETWEEN DNA REPLICATION AND DIVISION DURING THE CELL CYCLE OF TETRAHYMENA

Jeffery

1972

The Journal of Cell Biology

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The mechanism of coordination between DNA repl, cation and cell division was studied inTetrahymena pyriformis GL-C by manipulation of the timing of these events with heat shocks and inhibition of DNA synthesis. Preliminary experiments showed that the inhibitor combination methotrexate and uridine (M + U) was an effective inhibitor of DNA synthesis. Inhibition of the progression of DNA synthesis with M + U in exponentially growing cells, in which one S period usually occurs between two successive divisions, or in heat-shocked cells, when successive S periods are known to occur between divisions, resulted in the complete suppression of the following division. In further experiments in which the division activities were reassociated with the DNA synthetic cycle by premature termination of the heat-shock treatment, it was shown that (a) the completion of one S period during the treatment was sufficient for cell division, (b) the beginning of division events suppressed the initiation of further S periods, and (c) if further S periods were initiated while the heat-shock treatment was continued, division preparations could not begin until the necessary portion of the S period was completed, even though DNA had previously been duplicated. It was concluded that a temporal incompaubility exists between DNA synthesis and division which may reflect a coupling mechanism which insures their coordination during the normal cell cycle.

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Section: Extent and Specificity Of Inhibition Of Dna Synthesissupporting

confidence: 90%

Section: Extent and Specificity Of Inhibition Of Dna Synthesismentioning

confidence: 63%

Section: General Proceduresmentioning

confidence: 99%

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EVIDENCE FOR A TEMPORAL INCOMPATIBILITY BETWEEN DNA REPLICATION AND DIVISION DURING THE CELL CYCLE OF TETRAHYMENA

Jeffery

1972

The Journal of Cell Biology

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“…In short-term experiments, i.e. for about one cell generation, M + U was found to have little effect on RNA and protein synthesis (110), and during this period M + U is a very specific inhibitor of the DNA synthesis. However, M + U has an indirect effect on the RNA synthesis, since the doubling in rate of ribosomal RNA synthesis, which in synchronized cells occurs at the time when the ribosomal genes (rDNA) are replicated, is prevented when M + U blocks the replication of rDNA (66).…”

Section: The Inhibition Of Dna Synthesismentioning

confidence: 99%

“…The experiments revealed that all DNA in the population attained "hybrid density" during a period of 80-90 minutes after the division. This time corresponds to the duration of the Speriod in a single log-phase cell of about 60 minutes (25,110) plus the time within which the population divides (see figure 2). (109)).…”

Section: Dna Synthesis In Populations Exposed Tomentioning

confidence: 99%

Replication and functions of macronuclear DNA in synchronously growing populations of Tetrahymena pyriformis

Andersen

1977

Carlsberg Res. Commun.

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It is the objective of this article to discuss aspects of the macronuclear DNA replication and function in heat synchronized populations of Tetrahymena pyriformis. The thymidine analogue 5-bromodeoxyuridine was used as a density marker of synthesized DNA. This density label of DNA, followed by gradient centrifugation, was used to measure DNA replication quantitatively and to gain information about the nature of the DNA synthesis, which takes place at various periods of the cell cycle. Some of the events in the synchronized cell cycle, which are described, may be summarized briefly: After a synchronous cell division the cells initiate a synchronous replication of the macronuclear DNA. The DNA replication begins with replication of the ribosomal genes. Thereafter the bulk nuclear DNA replicates, and parallel with this the genes coding for 5S rRNA and tRNA. The replication of bulk DNA may follow a fixed sequence in each S-period, ensuring full replication of all DNA without double replication of any DNA fraction. However, the replication sequence changes from generation to generation, possibly due to a mixing of the nuclear subnuclei prior to division. The cells appear to have a full complement of genes replicated before the end of the macronuclear S-period. Obligatory DNA synthesis ends and G2-activities are initiated when 70-80% of the DNA has been replicated. The cells are able to divide after the DNA replication has been inhibited in the latter half the preceding S-period. Such ceils divide with a fraction of their DNA only partially replicated. This DNA fraction is eliminated from the macronucleus at the time of the division, and it is localized in the cytoplasm during the next cell generation. When the inhibitory treatment is removed at the time of cell division, the extruded DNA continues its replication after the end of the macronuclear S-period. Furthermore, it was found that thymidine starvation, here used as a specific inhibitor of DNA replication, tended to stop replication preferentially in regions of the molecules with relative high dAdT base content and leaving molecules with single stranded regions.Bromodeoxyuridine, which has been a valuable tool in the analysis of the DNA replication in Tetrahymena, is under special circumstances a potent inhibitor of macromotecular synthesis and cell proliferation. Bromodeoxyuridine has to be incorporated into DNA in high amounts before any inhibitory effects are seen. As soon as DNA contains bromodeoxyuridine in sufficient amounts, it will affect transcription, but the various genes respond differently to the substitution. The rDNA, i.e. the genes coding for the two large ribosomal RNA molecules (17S-and 25S RNA) were found to be most sensitive.

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Synchronization of the Tetrahymena Cell Cycle

Zeuthen

1971

Advances in Cell Biology

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Synchronization of DNA synthesis in Tetrahymena populations by temporary limitation of access to thymine compounds

Cited by 33 publications

References 15 publications

EVIDENCE FOR A TEMPORAL INCOMPATIBILITY BETWEEN DNA REPLICATION AND DIVISION DURING THE CELL CYCLE OF TETRAHYMENA

EVIDENCE FOR A TEMPORAL INCOMPATIBILITY BETWEEN DNA REPLICATION AND DIVISION DURING THE CELL CYCLE OF TETRAHYMENA

Replication and functions of macronuclear DNA in synchronously growing populations of Tetrahymena pyriformis

Synchronization of the Tetrahymena Cell Cycle

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