ANALYSIS OF THE SCHEDULE OF DNA REPLICATION IN HEAT-SYNCHRONIZED <i>TETRAHYMENA </i>

Jeffery, William R.; Frankel, Joseph; Bault, Lawrence E. De; Jenkins, Leslie M.

doi:10.1083/jcb.59.1.1

Cited by 16 publications

(4 citation statements)

References 29 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…exceedingly loose. As shown in this study and earlier in other strains of T. pyriformis by Jeffery et al (38,39) and Cleffmann (7-9), completion of a round of macronuclear DNA synthesis is not sufficient for cell division; two successive rounds of macronuclear DNA synthesis within one cell division cycle may occur even in undisturbed wildtype cells (8). Conversely, cell division cycles (including oral development) have been observed in the absence of ongoing macronuclear DNA synthesis after heat-shock synchronization in T. pyriformis (39,43) and normally in T. patula (30) and T. paravorax (14).…”

Section: Relationships Of Clusters Of Cell-cycle Processes: a Minimalsupporting

confidence: 92%

Causal relations among cell cycle processes in Tetrahymena pyriformis. An analysis employing temperature-sensitive mutants.

Frankel¹,

Jenkins²,

DeBault³

1976

The Journal of Cell Biology

View full text Add to dashboard Cite

Utilization of temperature-sensitive mutants of Tetrahymena pyriformis affected in cell division or developmental pathway selection has permitted elucidation of causal dependencies interrelating micronuclear and macronuclear replication and division, oral development, and cytokinesis. In those mutants in which cell division is specifically blocked at restrictive temperatures, micronuclear division proceeds with somewhat accelerated periodicity but maintains normal coupling to predivision oral development. Macronuclear division is almost totally suppressed in an early acting mutant (mol a) that prevents formation of the fission zone, and is variably affected in other mutants (such as mo3) that allow the fission zone to form but arrest constriction. However, macronuclear DNA synthesis can proceed for about four cycles in the nondividing mutant cells. A second class of mutants (psm) undergoes a switch of developmental pathway such that cells fail to enter division but instead repeatedly carry out an unusual type of oral replacement while growing in nutrient medium at the restrictive temperature. Under these circumstances no nuclei divide, yet macronuclear DNA accumulation continues. These results suggest that (a) macronuclear division is stringently affected by restriction of cell division, (b) micronuclear division and replication can continue in cells that are undergoing the type of oral development that is characteristic of division cycles, and (c) macronuclear DNA synthesis can continue in growing cells regardless of their developmental status. The observed relationships among events are consistent with the further suggestion that the cell cycle in this organism may consist of separate clusters of events, with a varying degree of coupling among clusters. A minimal model of the Tetrahymena cell cycle that takes these phenomena into account is suggested.One way to uncover causal relations between successive or simultaneous cellular developmental processes is to interfere selectively with one process and then observe the effects on the others. Microsurgical dissection provides a paradigm for this experimental logic: for example, Tartar (61) was able to demonstrate conclusively that the oral development of a ciliate is not necessary for the cell division that follows it, by simply cutting out the developing oral apparatus of Stentor and then observing that fission proceeds nonetheless. However, where cells are small and not readily operable, and/or the processes under study are pervasive physiological 242

show abstract

Section: Relationships Of Clusters Of Cell-cycle Processes: a Minimalsupporting

confidence: 92%

Causal relations among cell cycle processes in Tetrahymena pyriformis. An analysis employing temperature-sensitive mutants.

Frankel¹,

Jenkins²,

DeBault³

1976

The Journal of Cell Biology

View full text Add to dashboard Cite

show abstract

“…HJELM and ZEUTHEN (53) suggested that the heat treatment causes extension of the interval between the S-periods, whereas the duration of the S-period in the single cell is about normal. This suggestion has been confirmed by JEFFERY (61) and JEFFREY et al (62,63) in an autoradiographic study on single cells, and by CLEFFMAN (30) and it agrees well with the results from the experiments with BUdR (8). We may conclude that the heat shocks have little effect on the DNA replication, butthey do inhibit other division-relevant processes.…”

Section: Dna Synthesis In Cultures Exposed To Sevensupporting

confidence: 80%

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

Andersen

1977

Carlsberg Res. Commun.

View full text Add to dashboard Cite

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.

show abstract

“…Following the end of the last heat shock, 30-50% of the cells still undergo macronuclear DNA replication before entering the first synchronous division (Cerroni & Zeuthen, 1962;Hjelm & Zeuthen, 1967;Jeffery et al, 1970). These late DNAreplicating cells have not yet been shown to be the same cells that skip DNA replication during the first cell cycle but supporting evidence for this notion has been presented by Jeffery et al (1973). They showed that as the fraction of cells completing DNA replication prior to the end of the final heat shock increased, so did the fraction of cells participating in DNA replication during the first synchronous cell cycle.…”

Section: Cell Cycle Kinetics Of Hu-block Recovery Support the N/c Modelmentioning

confidence: 78%

Nucleocytoplasmic Ratio Requirements for the Initiation of Dna Replication and Fission in Tetrahymena

1976

View full text Add to dashboard Cite

Hydroxyurea (10 mM) arrests the exponential growth of Tetrahymena by blocking DNA replication during S‐phase. After removal of the hydroxyurea (HU), they have a long recovery period during which they are active in DNA synthesis. 3H‐TdR uptake showed that on completion of the recovery period, the cells divide (recovery division) and enter a cell cycle which lacks G1. The frequency, size and DNA content of the extranuclear chromatin bodies (ECB) formed at this division are all markedly increased (2–4) over the corresponding values obtained from exponential growth phase controls. Microspectrophotometric analysis of macronuclear DNA content (N) coupled with the cytoplasmic dry mass (C) values suggest that specific N to C ratios (N/C) are required for the initiation of DNA replication and fission: during a normal (exponential growth) cell cycle, both N and C double, but asynchronously, so that the N/C of both post‐fission‐daughter cells and pre‐fission cells is identical (standardized to N/C = 1) but late G1 cells have a low N/C. During a 10 hr exposure to HU, the N remains essentially the same whereas the C increases. When the HU is removed, the N increases by 4× and the C continues to increase until just prior to recovery division when it also reaches a value 4× that of the original daughter cells. Thus, the N/C = 1 is re‐established. The enlarged ECB formed during recovery division may function to lower the N/C in the daughter cells, which in turn may in some way stimulate immediate DNA replication, thus eliminating G1. The elimination of G1 (and shortening in a few subsequent cell cycles) allows less time for cytoplasmic growth and results in the return of the cells to the generation time and the N and C values observed prior to the HU treatment.

show abstract

ANALYSIS OF THE SCHEDULE OF DNA REPLICATION IN HEAT-SYNCHRONIZED TETRAHYMENA

Cited by 16 publications

References 29 publications

Causal relations among cell cycle processes in Tetrahymena pyriformis. An analysis employing temperature-sensitive mutants.

Causal relations among cell cycle processes in Tetrahymena pyriformis. An analysis employing temperature-sensitive mutants.

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

Nucleocytoplasmic Ratio Requirements for the Initiation of Dna Replication and Fission in Tetrahymena

Contact Info

Product

Resources

About