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 The proteasome controls ESCRT-III–mediated cell division in an archaeon

Science ◽  
2020 ◽  
Vol 369 (6504) ◽  
pp. eaaz2532 ◽  
Author(s):  
Gabriel Tarrason Risa ◽  
Fredrik Hurtig ◽  
Sian Bray ◽  
Anne E. Hafner ◽  
Lena Harker-Kirschneck ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Division Ring ◽  
Cell Cycle Control ◽  
Sulfolobus Acidocaldarius ◽  
Cyclin Dependent Kinase ◽  
Membrane Remodeling

Sulfolobus acidocaldarius is the closest experimentally tractable archaeal relative of eukaryotes and, despite lacking obvious cyclin-dependent kinase and cyclin homologs, has an ordered eukaryote-like cell cycle with distinct phases of DNA replication and division. Here, in exploring the mechanism of cell division in S. acidocaldarius, we identify a role for the archaeal proteasome in regulating the transition from the end of one cell cycle to the beginning of the next. Further, we identify the archaeal ESCRT-III homolog, CdvB, as a key target of the proteasome and show that its degradation triggers division by allowing constriction of the CdvB1:CdvB2 ESCRT-III division ring. These findings offer a minimal mechanism for ESCRT-III–mediated membrane remodeling and point to a conserved role for the proteasome in eukaryotic and archaeal cell cycle control.

Increase in macromolecular amounts during the cell cycle of Tetrahymena: a contribution to cell cycle control

1979 ◽  
Vol 37 (1) ◽  
pp. 117-124
Author(s):  
G. Cleffmann ◽  
W.O. Reuter ◽  
H.M. Seyfert
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Protein Content ◽  
Cell Size ◽  
Cell Cycle Control ◽  
Negative Control ◽  
Dna Amount ◽  
Protein Ratio ◽  
Initiation Of Dna Replication

Increases in RNA, protein and cell size were determined cytophotometrically during the cell division cycle of Tetrahymena. For these parameters different patterns were found. RNA accumulates slowly during G1 period and faster during macronuclear S. This agrees with the changing uridine incorporation rate which is at least partly related to the varying macronuclear DNA amount. Increases in protein content and cell size occur mainly during G1 and G2. This pattern was confirmed by determining the RNA: protein ratio in individual cells. It is minimal at the end of the G1 period. These findings and evidence from the literature suggest that initiation of DNA replication is under negative control by the relative RNA content of the cell.

scholarly journals Dynamics of pre-replication complex proteins during the cell division cycle

2004 ◽  
Vol 359 (1441) ◽  
pp. 7-16 ◽  
Author(s):  
Supriya G. Prasanth ◽  
Juan Méndez ◽  
Kannanganattu V. Prasanth ◽  
Bruce Stillman
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Dna Replication ◽  
Origin Recognition Complex ◽  
Cell Division Cycle ◽  
Vital Functions ◽  
A Cell ◽  
Bona Fide ◽  
Mcm Proteins ◽  
Key Participants

Replication of the human genome every time a cell divides is a highly coordinated process that ensures accurate and efficient inheritance of the genetic information. The molecular mechanism that guarantees that many origins of replication fire only once per cell–cycle has been the area of intense research. The origin recognition complex (ORC) marks the position of replication origins in the genome and serves as the landing pad for the assembly of a multiprotein, pre–replicative complex (pre–RC) at the origins, consisting of ORC, cell division cycle 6 (Cdc6), Cdc10–dependent transcript (Cdt1) and mini–chromosome maintenance (MCM) proteins. The MCM proteins serve as key participants in the mechanism that limits eukaryotic DNA replication to once–per–cell–cycle and its binding to the chromatin marks the final step of pre–RC formation, a process referred to as ‘replication licensing’. We present data demonstrating how the MCM proteins associate with the chromatin during the G1 phase, probably defining pre–RCs and then anticipate replication fork movement in a precisely coordinated manner during the S phase of the cell cycle. The process of DNA replication must also be carefully coordinated with other cell–cycle processes including mitosis and cytokinesis. Some of the proteins that control initiation of DNA replication are likely to interact with the pathways that control these important cell–cycle transitions. Herein, we discuss the participation of human ORC proteins in other vital functions, in addition to their bona fide roles in replication.

scholarly journals The cell cycle program of polypeptide labeling in Chlamydomonas reinhardtii.

1977 ◽  
Vol 72 (2) ◽  
pp. 223-241 ◽  
Author(s):  
S H Howell ◽  
J W Posakony ◽  
K R Hill
Keyword(s):  
Cell Cycle ◽  
Chlamydomonas Reinhardtii ◽  
Polyacrylamide Gel Electrophoresis ◽  
Sodium Dodecyl ◽  
Cell Generation ◽  
Temperature Sensitive ◽  
Dark Phase ◽  
Restrictive Temperature ◽  
One Dimensional ◽  
A Cell

The cell cycle program of polypeptide labeling in syndhronous cultures of wild-type Chlamydomonas reinhardtii was analyzed by pulse-labeling cells with 35SO4 = or [3H]arginine at different cell cycle stages. Nearly 100 labeled membrane and soluble polypeptides were resolved and studied using one-dimensional sodium dodecyl sulfate (SDS)-polyacrylamide gel electrophoresis. The labeling experiments produced the following results. (a) Total 35SO4 = and [3H]arginine incorporation rates varied independently throughout the cell cycle. 35SO4 = incorporation was highest in the mid-light phase, while [3H]arginine incorporation peaked in the dark phase just before cell division. (b) The relative labeling rate for 20 of 100 polypeptides showed significant fluctuations (3-12 fold) during the cell cycle. The remaining polypeptides were labeled at a rate commensurate with total 35SO4 = or [3H]arginine incorporation. The polypeptides that showed significant fluctuations in relative labeling rates served as markers to identify cell cycle stages. (c) The effects of illumination conditions on the apparent cell cycle stage-specific labeling of polypeptides were tested. Shifting light-grown asynchronous cells to the dark had an immediate and pronounced effect on the pattern of polypeptide labeling, but shifting dark-phase syndhronous cells to the light had little effect. The apparent cell cycle variations in the labeling of ribulose 1,5-biphosphate (RUBP)-carboxylase were strongly influenced by illumination effects. (d) Pulse-chase experiments with light-grown asynchronous cells revealed little turnover or inter-conversion of labeled polypeptides within one cell generation, meaning that major polypeptides, whether labeled in a stage-specific manner or not, do not appear transiently in the cell cycle of actively dividing, light-grown cells. The cell cycle program of labeling was used to analyze effects of a temperature-sensitive cycle blocked (cb) mutant. A synchronous culture of ts10001 was shifted to restrictive temperature before its block point to prevent it from dividing. The mutant continued its cell cycle program of polypeptide labeling for over a cell generation, despite its inability to divide.

scholarly journals MEIOTIC RECOMBINATION AND DNA SYNTHESIS IN A NEW CELL CYCLE MUTANT OF SACCHAROMYCES CEREVISIAE

Genetics ◽  
1978 ◽  
Vol 90 (1) ◽  
pp. 49-68
Author(s):  
Yona Kassir ◽  
Giora Simchen
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Dna Synthesis ◽  
Nuclear Division ◽  
Temperature Shift ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Essential Function ◽  
Normal Meiosis

ABSTRACT Vegetative cells carrying the new temperature-sensitive mutation cdc40 arrest at the restrictive temperature with a medial nuclear division phenotype. DNA replication is observed under these conditions, but most cells remain sensitive to hydroxyurea and do not complete the ongoing cell cycle if the drug is present during release from the temperature block. It is suggested that the cdc40 lesion affects an essential function in DNA synthesis. Normal meiosis is observed at the permissive temperature in cdc40 homozygotes. At the restrictive temperature, a full round of premeiotic DNA replication is observed, but neither commitment to recombination nor later meiotic events occur. Meiotic cells that are already committed to the recombination process at the permissive temperature do not complete it if transferred to the restrictive temperature before recombination is realized. These temperature shift-up experiments demonstrate that the CDC40 function is required for the completion of recombination events, as well as for the earlier stage of recombination commitment. Temperature shift-down experiments with cdc40 homozygotes suggest that meiotic segregation depends on the final events of recombination rather than on commitment to recombination.

scholarly journals GENETIC CONTROL OF THE CELL DIVISION CYCLE IN YEAST: V. GENETIC ANALYSIS OF cdc MUTANTS

Genetics ◽  
1973 ◽  
Vol 74 (2) ◽  
pp. 267-286
Author(s):  
Leland H Hartwell ◽  
Robert K Mortimer ◽  
Joseph Culotti ◽  
Marilyn Culotti
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Nuclear Gene ◽  
Temperature Shift ◽  
Time Lapse ◽  
Cell Division Cycle ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Gene Products ◽  
Diploid Cells

ABSTRACT One hundred and forty-eight temperature-sensitive cell division cycle (cdc) mutants of Saccharomyces cerevisiae have been isolated and characterized. Complementation studies ordered these recessive mutations into 32 groups and tetrad analysis revealed that each of these groups defines a single nuclear gene. Fourteen of these genes have been located on the yeast genetic map. Functionally related cistrons are not tightly clustered. Mutations in different cistrons frequently produce different cellular and nuclear morphologies in the mutant cells following incubation at the restrictive temperature, but all the mutations in the same cistron produce essentially the same morphology. The products of these genes appear, therefore, each to function individually in a discrete step of the cell cycle and they define collectively a large number of different steps. The mutants were examined by time-lapse photomicroscopy to determine the number of cell cycles completed at the restrictive temperature before arrest. For most mutants, cells early in the cell cycle at the time of the temperature shift (before the execution point) arrest in the first cell cycle while those later in the cycle (after the execution point) arrest in the second cell cycle. Execution points for allelic mutations that exhibit first or second cycle arrest are rather similar and appear to be cistron-specific. Other mutants traverse several cycles before arrest, and its suggested that the latter type of response may reveal gene products that are temperature-sensitive for synthesis, whereas the former may be temperature-sensitive for function. The gene products that are defined by the cdc cistrons are essential for the completion of the cell cycle in haploids of a and α mating type and in a/α diploid cells. The same genes, therefore, control the cell cycle in each of these stages of the life cycle.

scholarly journals CONDITIONAL MUTANTS IN CHLAMYDOMONAS REINHARDTII BLOCKED IN THE VEGETATIVE CELL CYCLE

1973 ◽  
Vol 57 (3) ◽  
pp. 760-772 ◽  
Author(s):  
Stephen H. Howell ◽  
Jay A. Naliboff
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Chlamydomonas Reinhardtii ◽  
Simple Technique ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
General Applicability ◽  
Cell Cycles ◽  
Point Analysis ◽  
A Cell

Conditional "cycle-blocked" (cb) mutants of Chlamydomonas reinhardtii have been detected and isolated. These mutants exhibit normal vegetative growth at permissive temperature but are unable to complete a cell cycle (or a specified number of cell cycles) at restrictive temperature. A simple technique has been devised to determine the cell cycle stage in each mutant when the defective gene product, which ultimately affects cell division, completes its function. This stage is called the "block point", and is determined by scoring the residual cell division in an exponentially growing population after shift to temperature restrictive conditions. In the cb mutants isolated so far, block points representing many stages throughout the cell cycle have been found. Two categories of cb mutants are described here: one set which prevents the subsequent cell division when the cell encounters the block point after a shift to restrictive temperature, and another set which permits an additional round of cell division after the block point is encountered. The general applicability of block point analysis to other cell systems is presented.

scholarly journals Functions of Fission Yeast Orp2 in DNA Replication and Checkpoint Control

Genetics ◽  
2000 ◽  
Vol 154 (2) ◽  
pp. 599-607
Author(s):  
Joan Kiely ◽  
S B Haase ◽  
Paul Russell ◽  
Janet Leatherwood
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Cell Cycle Arrest ◽  
Fission Yeast ◽  
Replication Initiation ◽  
Initiation Factor ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Checkpoint Control ◽  
Cycle Arrest

Abstract orp2 is an essential gene of the fission yeast Schizosaccharomyces pombe with 22% identity to budding yeast ORC2. We isolated temperature-sensitive alleles of orp2 using a novel plasmid shuffle based on selection against thymidine kinase. Cells bearing the temperature-sensitive allele orp2-2 fail to complete DNA replication at a restrictive temperature and undergo cell cycle arrest. Cell cycle arrest depends on the checkpoint genes rad1 and rad3. Even when checkpoint functions are wild type, the orp2-2 mutation causes high rates of chromosome and plasmid loss. These phenotypes support the idea that Orp2 is a replication initiation factor. Selective spore germination allowed analysis of orp2 deletion mutants. These experiments showed that in the absence of orp2 function, cells proceed into mitosis despite a lack of DNA replication. This suggests either that the Orp2 protein is a part of the checkpoint machinery or more likely that DNA replication initiation is required to induce the replication checkpoint signal.

scholarly journals Residual cell division measurements are unreliable as indicators of the timing of events in the Saccharomyces cerevisiae cell cycle

1983 ◽  
Vol 64 (1) ◽  
pp. 307-322
Author(s):  
K.M. Richmond ◽  
D.H. Williamson
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Temperature Shift ◽  
Growth Conditions ◽  
Population Doubling ◽  
Population Doubling Time ◽  
Temperature Sensitive ◽  
Restrictive Temperature ◽  
Point Data

We report here an analysis of the execution point of the temperature-sensitive Saccharomyces cerevisiae cell cycle mutant, cdc27-47. When a logarithmically growing culture was shifted from standard growth conditions (strain 27.8B growing in YEPD at 25 degrees C) to the restrictive temperature cell division ceased abruptly and reproducibly within one population doubling time, the extent of cell division indicating an execution point early in the cell cycle. Approximately 50% of stationary-phase cells were able to divide when refed with fresh medium at 37 degrees C, showing that the execution point could be passed before ‘start’. This makes the sharp cut-off in cell division difficult to explain. This difficulty was compounded by observations of the cell cycle stage at which individual cells acquired the capacity to divide at 37 degrees C. Half the cells that were budded at the time of a temperature shift-up formed three division-blocked cells, and in 11 of these 13 cases, two were descended from the original mother cell and one from the original bud. Thus, mother and daughter cells pass the execution point independently; daughters usually during G1, and mothers usually in the budded phase of the previous cycle. The sharp cut-off in cell division is therefore spurious, and a mechanism is proposed to account for it, which has implications for the interpretation of the execution points of other cdc mutants. In addition, the expression of the cdc27-47 execution point was modified by both genetic and environmental factors, being affected by carbon source, by the petite condition, and by genetic background. This illustrates the difficulties of interpreting execution point data and the dangers of extrapolation of cell cycle parameters between strains and growth conditions.

scholarly journals An ATM/Wip1-dependent timer controls the minimal duration of a DNA-damage mediated cell cycle arrest

2016 ◽  
Author(s):  
Himjyot Jaiswal ◽  
Jan Benada ◽  
Erik Mullers ◽  
Karen Akopyan ◽  
Kamila Burdova ◽  
...  
Keyword(s):  
Experimental Data ◽  
Cell Cycle ◽  
Dna Damage ◽  
Cell Cycle Arrest ◽  
Dna Lesions ◽  
Cycle Arrest ◽  
Checkpoint Adaptation ◽  
Global Spread ◽  
A Cell ◽  
G2 Phase

After DNA damage, the cell cycle is arrested to avoid propagation of mutations. In G2 phase, the arrest is initiated by ATM/ATR-dependent signalling that blocks mitosis-promoting kinases as Plk1. Interestingly, Plk1 can counteract ATR-dependent signalling and is required for eventual resumption of the cell cycle. However, what determines when Plk1 activity can resume remains unclear. Here we use FRET-based reporters to show that a global spread of ATM activity on chromatin and phosphorylation of targets including Kap1 control Plk1 re-activation. These phosphorylations are rapidly counteracted by the chromatin-bound phosphatase Wip1, allowing a cell cycle restart despite persistent ATM activity present at DNA lesions. Combining experimental data and mathematical modelling we propose that the minimal duration of a cell cycle arrest is controlled by a timer. Our model shows how cell cycle re-start can occur before completion of DNA repair and suggests a mechanism for checkpoint adaptation in human cells.

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