Free, Conjugated and Bound Polyamines during the Ceil Cycle in Synchronized Cultures of Scenedesmus obliquus

1994 ◽  
Vol 49 (3-4) ◽  
pp. 181-185 ◽  
Author(s):  
Kiriakos Kotzabasis ◽  
Horst Senger
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Scenedesmus Obliquus ◽  
Photosynthetic Apparatus ◽  
Membrane Systems ◽  
Additional Peak ◽  
Unicellular Green Alga ◽  
Synchronized Cultures

The levels of free, conjugated and bound polyamines (PA) were analyzed during the cell cycle of the synchronized unicellular green alga Scenedesmus obliquus. The polyamines putrescine (PUT) and spermidine (SPD) in their free and conjugated forms accumulated per cell to a maximum in the cell cycle at about the 16 th hour after onset of illumination. The polyamines bound to macromolecules and membrane systems showed an additional peak around the 8-10 th hour of the cell cycle. The possible role of the different forms of polyamines in DNA replication, mitosis, cell division and development of the photosynthetic apparatus is discussed

scholarly journals Role of the CtrA cell cycle regulator in the bloodborne bacterial pathogen, Bartonella quintana.

2021 ◽  
Author(s):  
◽  
Robert Haydn Thomson
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Binding Sites ◽  
Caulobacter Crescentus ◽  
Regulatory Regions ◽  
Bartonella Quintana ◽  
Cell Cycle Regulator ◽  
Wide Range

<p>Bartonella quintana is an important re-emerging human pathogen and the causative agent of trench fever. It utilizes a stealth invasion strategy to infect hosts and is transmitted by lice. Throughout infection it is crucial for the bacteria to maintain a tight regulation of cell division, to prevent immune detection and allow for transmission to new hosts. CtrA is an essential master cell cycle regulatory protein found in the alpha-proteobacteria. It regulates many genes, ensuring the appropriate timing of gene expression and DNA replication. In the model organism Caulobacter crescentus, it regulates 26% of cell cycle-regulated genes. CtrA has been reported to bind two specific DNA motifs in gene promoter regions, TTAAN7TTAAC, and TTAACCAT. Genes regulated by CtrA encode proteins with a wide range of activities, including initiation of DNA replication, cell division, DNA methylation, polar morphogenesis, flagellar biosynthesis, and cell wall metabolism. However, the role of the CtrA homologue in Bartonella spp. has not been investigated. In this project we aimed to make an initial characterisation of the master cell cycle regulator CtrA. This was done by identifying gene regulatory regions containing putative CtrA binding sites and testing for direct interactions via a -galactosidase assay. It was found B. quintana CtrA shared 81 % amino acid identity with its C. crescentus homologue. Within the genome of B. quintana str. Toulouse we discovered 21 genes containing putative CtrA binding sites in their regulatory regions. Of these genes we demonstrated interactions between CtrA and the promoter region of ftsE a cell division gene [1], hemS, and hbpC, two heme regulatory genes. We also found no evidence of CtrA regulating its own expression, which was unexpected because CtrA autoregulation has been demonstrated in C. crescentus.</p>

scholarly journals Role of the CtrA cell cycle regulator in the bloodborne bacterial pathogen, Bartonella quintana.

2021 ◽  
Author(s):  
◽  
Robert Haydn Thomson
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Binding Sites ◽  
Caulobacter Crescentus ◽  
Regulatory Regions ◽  
Bartonella Quintana ◽  
Cell Cycle Regulator ◽  
Wide Range

<p>Bartonella quintana is an important re-emerging human pathogen and the causative agent of trench fever. It utilizes a stealth invasion strategy to infect hosts and is transmitted by lice. Throughout infection it is crucial for the bacteria to maintain a tight regulation of cell division, to prevent immune detection and allow for transmission to new hosts. CtrA is an essential master cell cycle regulatory protein found in the alpha-proteobacteria. It regulates many genes, ensuring the appropriate timing of gene expression and DNA replication. In the model organism Caulobacter crescentus, it regulates 26% of cell cycle-regulated genes. CtrA has been reported to bind two specific DNA motifs in gene promoter regions, TTAAN7TTAAC, and TTAACCAT. Genes regulated by CtrA encode proteins with a wide range of activities, including initiation of DNA replication, cell division, DNA methylation, polar morphogenesis, flagellar biosynthesis, and cell wall metabolism. However, the role of the CtrA homologue in Bartonella spp. has not been investigated. In this project we aimed to make an initial characterisation of the master cell cycle regulator CtrA. This was done by identifying gene regulatory regions containing putative CtrA binding sites and testing for direct interactions via a -galactosidase assay. It was found B. quintana CtrA shared 81 % amino acid identity with its C. crescentus homologue. Within the genome of B. quintana str. Toulouse we discovered 21 genes containing putative CtrA binding sites in their regulatory regions. Of these genes we demonstrated interactions between CtrA and the promoter region of ftsE a cell division gene [1], hemS, and hbpC, two heme regulatory genes. We also found no evidence of CtrA regulating its own expression, which was unexpected because CtrA autoregulation has been demonstrated in C. crescentus.</p>

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.

scholarly journals Cell cycle arrest of cdc mutants and specificity of the RAD9 checkpoint.

Genetics ◽  
1993 ◽  
Vol 134 (1) ◽  
pp. 63-80 ◽  
Author(s):  
T A Weinert ◽  
L H Hartwell
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Cycle Control ◽  
Dna Lesions ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
A Cell ◽  
G2 Phase ◽  
Rad Mutants

Abstract In eucaryotes a cell cycle control called a checkpoint ensures that mitosis occurs only after chromosomes are completely replicated and any damage is repaired. The function of this checkpoint in budding yeast requires the RAD9 gene. Here we examine the role of the RAD9 gene in the arrest of the 12 cell division cycle (cdc) mutants, temperature-sensitive lethal mutants that arrest in specific phases of the cell cycle at a restrictive temperature. We found that in four cdc mutants the cdc rad9 cells failed to arrest after a shift to the restrictive temperature, rather they continued cell division and died rapidly, whereas the cdc RAD cells arrested and remained viable. The cell cycle and genetic phenotypes of the 12 cdc RAD mutants indicate the function of the RAD9 checkpoint is phase-specific and signal-specific. First, the four cdc RAD mutants that required RAD9 each arrested in the late S/G2 phase after a shift to the restrictive temperature when DNA replication was complete or nearly complete, and second, each leaves DNA lesions when the CDC gene product is limiting for cell division. Three of the four CDC genes are known to encode DNA replication enzymes. We found that the RAD17 gene is also essential for the function of the RAD9 checkpoint because it is required for phase-specific arrest of the same four cdc mutants. We also show that both X- or UV-irradiated cells require the RAD9 and RAD17 genes for delay in the G2 phase. Together, these results indicate that the RAD9 checkpoint is apparently activated only by DNA lesions and arrests cell division only in the late S/G2 phase.

scholarly journals Cell Cycle-Specific Disruption of the Preprophase Band of Microtubules in Fern Protonemata: Effects of Displacement of the Endoplasm by Centrifugation

1992 ◽  
Vol 101 (1) ◽  
pp. 93-98 ◽  
Author(s):  
TAKASHI MURATA ◽  
MASAMITSU WADA
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Plant Cells ◽  
Preprophase Band ◽  
Higher Plant ◽  
The Future ◽  
Prophase Nucleus ◽  
Original Region ◽  
Fern Protonemata

The preprophase band (PPB) of microtubules (MTs), which appears at the future site of cytokinesis prior to cell division in higher plant cells, disappears by metaphase. Recent studies have shown that displacement of the endoplasm from the PPB region by centrifugation delays the disappearance of the PPB. To study the role of the endoplasm in the cell cycle-specific disruption of the PPB, the filamentous protonemal cells of the fern Adiantum capilius-veneris L. were centrifuged twice so that the first centrifugation displaced the endoplasm from the site of the PPB and the second returned it to its original location. The endoplasm, including the nucleus of various stages of mitosis, could be returned by the second centrifugation to the original region of the PPB, which persists during mitosis in the centrifuged cells. When endoplasm with a prophase nucleus was returned to its original location, the PPB was not disrupted. When endoplasm with a prometa-phase telophase nucleus was similarly returned, the PPB was disrupted within 10 min of termination of centrifugation. In protonemal cells of Adiantum, a second PPB is often formed near the displaced nucleus after the first centrifugation. In cells in which the endoplasm was considered to have been returned to its original location at the prophase/prometaphase transition, the second PPB did not disappear even though the initial PPB was disrupted by the endoplasm. These results suggest that cell cycle-specific disruption of the PPB is regulated by some factor(s) in the endoplasm, which appears at prometaphase, i.e. the stage at which the PPB is disrupted in non-centrifuged cells.

Essential role of human CDT1 in DNA replication and chromatin licensing

2002 ◽  
Vol 115 (7) ◽  
pp. 1435-1440 ◽  
Author(s):  
Mickael Rialland ◽  
Francesco Sola ◽  
Corrado Santocanale
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Complex Formation ◽  
Fission Yeast ◽  
Origin Recognition Complex ◽  
Essential Role ◽  
Large Body ◽  
Transformed Cells ◽  
Minichromosome Maintenance

Formation of pre-replicative complexes at origins is an early cell cycle event essential for DNA duplication. A large body of evidence supports the notion that Cdc6 protein, through its interaction with the origin recognition complex, is required for pre-replicative complex assembly by loading minichromosome maintenance proteins onto DNA. In fission yeast and Xenopus, this reaction known as the licensing of chromatin for DNA replication also requires the newly identified Cdt1 protein. We studied the role of hCdt1 protein in the duplication of the human genome by antibody microinjection experiments and analyzed its expression during the cell cycle in human non-transformed cells. We show that hCdt1 is essential for DNA replication in intact human cells, that it executes its function in a window of the cell cycle overlapping with pre-replicative complex formation and that it is necessary for the loading of minichromosome maintenance proteins onto chromatin. Intriguingly, we observed that hCdt1 protein, in contrast to other licensing factors, is already present in serum-deprived G0 arrested cells and its levels increase only marginally upon re-entry in the cell cycle.

Role of transcriptional and posttranscriptional regulation in expression of histone genes in Saccharomyces cerevisiae

1987 ◽  
Vol 7 (2) ◽  
pp. 614-621
Author(s):  
D E Lycan ◽  
M A Osley ◽  
L M Hereford
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Dna Replication ◽  
Posttranscriptional Regulation ◽  
Cell Cycle Control ◽  
Dimensional Structure ◽  
Histone Genes ◽  
Transcriptional Regulatory Mechanisms ◽  
Rna Levels

We analyzed the role of posttranscriptional mechanisms in the regulation of histone gene expression in Saccharomyces cerevisiae. The rapid drop in histone RNA levels associated with the inhibition of ongoing DNA replication was postulated to be due to posttranscriptional degradation of histone transcripts. However, in analyzing the sequences required for this response, we showed that the coupling of histone RNA levels to DNA replication was due mostly, if not entirely, to transcriptional regulatory mechanisms. Furthermore, deletions which removed the negative, cell cycle control sequences from the histone promoter also uncoupled histone transcription from DNA replication. We propose that the arrest of DNA synthesis prematurely activates the regulatory pathway used in the normal cell cycle to repress transcription. Although posttranscriptional regulation did not appear to play a significant role in coupling histone RNA levels to DNA replication, it did affect the levels of histone RNA in the cell cycle. Posttranscriptional regulation could apparently restore much of the periodicity of histone RNA accumulation in cells which constitutively transcribed the histone genes. Unlike transcriptional regulation, periodic posttranscriptional regulation appears to operate on a clock which is independent of events in the mitotic DNA cycle. Posttranscriptional recognition of histone RNA must require either sequences in the 3' end of the RNA or an intact three-dimensional structure since H2A- and H2B-lacZ fusion transcripts, containing only 5' histone sequences, were insensitive to posttranscriptional controls.

Wachstumsparameter in normalen und durch Actinomycin verlängerten Zellzyklen von Tetrahymena / Growth Parameters in Normal and Actinomycin-induced prolonged Cell Cycles of Tetrahymena

1969 ◽  
Vol 24 (12) ◽  
pp. 1624-1629 ◽  
Author(s):  
Günter Cleffmann
Keyword(s):  
Cell Cycle ◽  
Protein Synthesis ◽  
Cell Division ◽  
Dna Replication ◽  
Cell Growth ◽  
Rna Synthesis ◽  
Growth Parameters ◽  
Average Duration ◽  
Cell Cycles ◽  
Growing Cell

Actinomycin in low concentration (0,2 μg/ml — 0,5 μg/ml) prolongs the average duration of the cell cycle of Tetrahymena considerably, but does not inhibit cell division completely. Some parameters of the growing cell have been tested in cell cycles extended in this way and compared to those of normally growing cells. The RNA synthesis of treated cells is reduced to such an extent that the RNA content per cell decreases during the prolonged cell cycle. Nevertheless cell growth, protein synthesis and DNA replication proceed at almost the same rate as in untreated cells. These findings indicate that the presence of actinomycin does not interfere with RNA fractions necessary for growth but reduce the synthesis of RNA fractions which are essential for cell division. Therefore a longer period is needed for their accumulation.

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