scholarly journals THE EFFECT OF 5-BROMODEOXYURIDINE ON DNA REPLICATION AND CELL DIVISION IN TETRAHYMENA PYRIFORMIS

1974 ◽  
Vol 62 (2) ◽  
pp. 316-321 ◽  
Author(s):  
Anne E. Lykkesfeldt ◽  
H. A. Andersen
Keyword(s):  
Cell Division ◽  
Structural Change ◽  
Dna Replication ◽  
First Generation ◽  
Normal Growth ◽  
Tetrahymena Pyriformis ◽  
Defined Medium ◽  
Chemically Defined Medium ◽  
Normal Hybrid ◽  
Hybrid Dna

Populations of Tetrahymena pyriformis were grown in a chemically defined medium containing the thymidine analogue 5-bromodeoxyuridine (BUdR). About 65% of the thymidine sites in DNA were substituted by BUdR. During the first generation in the presence of BUdR, all DNA became hybrid. After the following cell division, in about 80% of the cells the second DNA replication round was initiated but no further cell division took place. The cells could be rescued by removing BUdR and adding thymidine. New replication took place before the first cell division. However, although the cells contained double heavy as well as hybrid DNA, only the hybrid DNA was replicated. After a full replication of the hybrid DNA, normal growth was restored. Melting profiles of normal, hybrid, and double heavy DNA indicated a structural change of the double heavy DNA.

Inhibition of rRNA synthesis following incorporation of 5-bromodeoxyuridine into DNA of Tetrahymena pyriformis

1975 ◽  
Vol 17 (3) ◽  
pp. 495-502
Author(s):  
A.E. Lykkesfeldt ◽  
H.A. Andersen
Keyword(s):  
Dna Replication ◽  
Ribosomal Rna ◽  
Rna Synthesis ◽  
Nuclear Dna ◽  
Tetrahymena Pyriformis ◽  
Growth Conditions ◽  
Defined Medium ◽  
Rrna Synthesis ◽  
Chemically Defined Medium ◽  
Dividing Cells

Tetrahymena pyriformis was grown on chemically defined medium in the presence of 5-bromodeoxyuridine (BUdR). Under these growth conditions more than 60% of the thymidine sites in DNA were substituted with BUdR. It was found that RNA synthesis was strongly inhibited by the presence of BUdR in DNA. To assure that incorporation of BUdR into DNA was a prerequisite of the effect observed, BUdR was added to synchronously dividing cells. BUdR had no effect on the cells when present outside the period of nuclear DNA replication, whereas RNA synthesis was strongly inhibited as soon as the genes coding for ribosomal RNA had replicated in the presence of BUdR.

scholarly journals Evidence for the lack of deoxyribonucleic acid dark-repair in Halobacterium cutirubrum

1976 ◽  
Vol 156 (3) ◽  
pp. 569-575 ◽  
Author(s):  
V L Grey ◽  
P S Fitt
Keyword(s):  
Dna Replication ◽  
Dna Synthesis ◽  
Deoxyribonucleic Acid ◽  
Normal Growth ◽  
Dark Repair ◽  
Hybrid Dna

1. Halobacterium cutirubrum does not perform dark-repair of DNA either after u.v. irradiation or during normal growth. 2. Cultures irradiated with u.v. are readily photoreactivated, but do not recover viability in the dark. 3. No increase in the rate of DNA synthesis is observed in the surviving cells after u.v. irradiation. 4. At early times during normal semiconservative replication, newly incorporated thymidine is found only in the hybrid DNA. 5. It is suggested that these bacteria may be useful in the study of DNA replication and photoreactivation.

scholarly journals MACROMOLECULAR EVENTS LEADING TO CELL DIVISION IN TETRAHYMENA PYRIFORMIS AFTER REMOVAL AND REPLACEMENT OF REQUIRED PYRIMIDINES

1965 ◽  
Vol 25 (2) ◽  
pp. 9-19 ◽  
Author(s):  
Ivan L. Cameron
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Nuclear Dna ◽  
Early Period ◽  
Tetrahymena Pyriformis ◽  
Cell Number ◽  
Cellular Protein ◽  
Cellular Content ◽  
Endogenous Protein

Tetrahymena pyriformis were brought to a non-growing state by removal of pyrimidines from their growth medium. During pyrimidine deprivation cell number increased 3- to 4 fold, and this increase was accompanied by one or more complete cycles of macronuclear DNA replication. Autoradiographic studies show that endogenous protein and RNA were turning over throughout starvation and that RNA breakdown products were used to support the DNA synthesis that occurred during the early period of starvation. However, after 72 hours of starvation all DNA synthesis and cell division had ceased. Feulgen microspectrophotometry shows the macronuclei of these cells to have been stopped at a point prior to DNA replication (G1 stage). After pyrimidine replacement the incorporation of H3-uridine, H3-adenosine, and H3-leucine was measured by the autoradiographic grain counting method. The results indicate that RNA synthesis began to increase almost immediately, but that there was a lag of almost an hour before an increase in protein synthesis. In agreement with the autoradiographic data, chemical data also show that cellular content of RNA began to increase shortly after pyrimidine replacement but that cellular protein content did not increase until about one hour later. Pulse labeling of the cells with H3-thymidine at intervals after pyrimidine replacement shows that labeled macronuclei first began to appear at 150 minutes; that 98 per cent of the macronuclei were in DNA synthesis at 240 to 270 minutes; and that the percentage then began to decrease from 300 to 390 minutes, at which time only 25 per cent of the macronuclei were labeled. Cellular content of DNA did not increase for at least 135 minutes after pyrimidine replacement; however, just before the first cells divided (360 minutes) the DNA content had doubled. After pyrimidine replacement the cells first began to divide at 360 minutes, and 50 per cent had divided at 420 minutes; however, all cells had not divided until 573 minutes. This technique of chemical synchronization of cells in mass cultures makes feasible detailed biochemical analysis of events leading to nuclear DNA replication and cell division.

Replication of Macronuclear DNA in the Cytoplasm of Tetrahymena Pyriformis

1974 ◽  
Vol 14 (2) ◽  
pp. 289-300
Author(s):  
H. A. ANDERSEN
Keyword(s):  
Cell Division ◽  
Dna Replication ◽  
Nuclear Dna ◽  
Tetrahymena Pyriformis ◽  
Cell Generation ◽  
The Other ◽  
Previous Generation ◽  
Cytoplasmic Dna ◽  
Continue Growth ◽  
S Period

Previous experiments showed that a synchronous population of Tetrahymena could divide even though DNA replication was blocked during the latter half of the preceding S-period by addition of methotrexate plus uridine (M + U). Furthermore, it was found that the DNA fraction which was in replication at the time of inhibition became localized in the cytoplasm following elimination from the nucleus at the time of division. When the inhibitory treatment (M + U) was removed prior to or at the time of the cell division the cells were found to engage in new DNA replication and continue growth. Two questions arose from these studies. First, is the DNA replication normal following release from M + U? Second, what is the fate of the cytoplasmic DNA? In the present paper DNA replication has been studied using incorporation of 5-bromodeoxyuridine and centrifugation of the labelled DNA in CsCl gradients. It is concluded that the DNA which finished replication prior to the effect of the M + U treatment replicates again during the S-period of the next cell generation. On the other hand, the DNA fraction which was stalled in replication and subsequently eliminated from the nucleus also replicates in the cytoplasm in the next generation but during G2 period, out of phase with the undamaged nuclear DNA. The cytoplasmic DNA replication appeared to be a continuation of the replication initiated in the nucleus in the previous generation.

scholarly journals Regulation of Cell Division in Bacteria by Monitoring Genome Integrity and DNA Replication Status

2019 ◽  
Vol 202 (2) ◽  
Author(s):  
Peter E. Burby ◽  
Lyle A. Simmons
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Progression ◽  
Genome Instability ◽  
Sos Response ◽  
Bacterial Cells ◽  
Cycle Progression ◽  
Content Type

ABSTRACT All organisms regulate cell cycle progression by coordinating cell division with DNA replication status. In eukaryotes, DNA damage or problems with replication fork progression induce the DNA damage response (DDR), causing cyclin-dependent kinases to remain active, preventing further cell cycle progression until replication and repair are complete. In bacteria, cell division is coordinated with chromosome segregation, preventing cell division ring formation over the nucleoid in a process termed nucleoid occlusion. In addition to nucleoid occlusion, bacteria induce the SOS response after replication forks encounter DNA damage or impediments that slow or block their progression. During SOS induction, Escherichia coli expresses a cytoplasmic protein, SulA, that inhibits cell division by directly binding FtsZ. After the SOS response is turned off, SulA is degraded by Lon protease, allowing for cell division to resume. Recently, it has become clear that SulA is restricted to bacteria closely related to E. coli and that most bacteria enforce the DNA damage checkpoint by expressing a small integral membrane protein. Resumption of cell division is then mediated by membrane-bound proteases that cleave the cell division inhibitor. Further, many bacterial cells have mechanisms to inhibit cell division that are regulated independently from the canonical LexA-mediated SOS response. In this review, we discuss several pathways used by bacteria to prevent cell division from occurring when genome instability is detected or before the chromosome has been fully replicated and segregated.

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