scholarly journals Protein synthesis requirements for nuclear division, cytokinesis, and cell separation in Saccharomyces cerevisiae.

1991 ◽  
Vol 11 (7) ◽  
pp. 3691-3698 ◽  
Author(s):  
D J Burke ◽  
D Church
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Protein Synthesis ◽  
Cell Division ◽  
Cell Separation ◽  
Nuclear Division ◽  
S Phase ◽  
Protein Synthesis Inhibitors ◽  
Yeast Saccharomyces Cerevisiae ◽  
Chemical Inhibitors

Protein synthesis inhibitors have often been used to identify regulatory steps in cell division. We used cell division cycle mutants of the yeast Saccharomyces cerevisiae and two chemical inhibitors of translation to investigate the requirements for protein synthesis for completing landmark events after the G1 phase of the cell cycle. We show, using cdc2, cdc6, cdc7, cdc8, cdc17 (38 degrees C), and cdc21 (also named tmp1) mutants, that cells arrested in S phase complete DNA synthesis but cannot complete nuclear division if protein synthesis is inhibited. In contrast, we show, using cdc16, cdc17 (36 degrees C), cdc20, cdc23, and nocodazole treatment, that cells that arrest in the G2 stage complete nuclear division in the absence of protein synthesis. Protein synthesis is required late in the cell cycle to complete cytokinesis and cell separation. These studies show that there are requirements for protein synthesis in the cell cycle, after G1, that are restricted to two discrete intervals.

Protein synthesis requirements for nuclear division, cytokinesis, and cell separation in Saccharomyces cerevisiae

1991 ◽  
Vol 11 (7) ◽  
pp. 3691-3698
Author(s):  
D J Burke ◽  
D Church
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Protein Synthesis ◽  
Cell Division ◽  
Cell Separation ◽  
Nuclear Division ◽  
S Phase ◽  
Protein Synthesis Inhibitors ◽  
Yeast Saccharomyces Cerevisiae ◽  
Chemical Inhibitors

Protein synthesis inhibitors have often been used to identify regulatory steps in cell division. We used cell division cycle mutants of the yeast Saccharomyces cerevisiae and two chemical inhibitors of translation to investigate the requirements for protein synthesis for completing landmark events after the G1 phase of the cell cycle. We show, using cdc2, cdc6, cdc7, cdc8, cdc17 (38 degrees C), and cdc21 (also named tmp1) mutants, that cells arrested in S phase complete DNA synthesis but cannot complete nuclear division if protein synthesis is inhibited. In contrast, we show, using cdc16, cdc17 (36 degrees C), cdc20, cdc23, and nocodazole treatment, that cells that arrest in the G2 stage complete nuclear division in the absence of protein synthesis. Protein synthesis is required late in the cell cycle to complete cytokinesis and cell separation. These studies show that there are requirements for protein synthesis in the cell cycle, after G1, that are restricted to two discrete intervals.

scholarly journals Replication fork rate and origin activation during the S phase of Saccharomyces cerevisiae.

1980 ◽  
Vol 85 (1) ◽  
pp. 108-115 ◽  
Author(s):  
C J Rivin ◽  
W L Fangman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cycle Length ◽  
Replication Fork ◽  
Nitrogen Sources ◽  
S Phase ◽  
Phase Duration ◽  
Yeast Saccharomyces Cerevisiae ◽  
Origin Activation ◽  
Cell Cycle Length

When the growth rate of the yeast Saccharomyces cerevisiae is limited with various nitrogen sources, the duration of the S phase is proportional to cell cycle length over a fourfold range of growth rates (C.J. Rivin and W. L. Fangman, 1980, J. Cell Biol. 85:96-107). Molecular parameters of the S phases of these cells were examined by DNA fiber autoradiography. Changes in replication fork rate account completely for the changes in S-phase duration. No changes in origin-to-origin distances were detected. In addition, it was found that while most adjacent replication origins are activated within a few minutes of each other, new activations occur throughout the S phase.

scholarly journals Checkpoint genes required to delay cell division in response to nocodazole respond to impaired kinetochore function in the yeast Saccharomyces cerevisiae.

1995 ◽  
Vol 15 (12) ◽  
pp. 6838-6844 ◽  
Author(s):  
Y Wang ◽  
D J Burke
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Yeast Saccharomyces Cerevisiae ◽  
Cell Cycle Delay ◽  
Delay Cell ◽  
Antimitotic Drugs ◽  
Checkpoint Genes ◽  
Spindle Structure ◽  
Kinetochore Function

Inhibition of mitosis by antimitotic drugs is thought to occur by destruction of microtubules, causing cells to arrest through the action of one or more mitotic checkpoints. We have patterned experiments in the yeast Saccharomyces cerevisiae after recent studies in mammalian cells that demonstrate the effectiveness of antimitotic drugs at concentrations that maintain spindle structure. We show that low concentrations of nocodazole delay cell division under the control of the previously identified mitotic checkpoint genes BUB1, BUB3, MAD1, and MAD2 and independently of BUB2. The same genes mediate the cell cycle delay induced in ctf13 mutants, limited for an essential kinetochore component. Our data suggest that a low concentration of nocodazole induces a cell cycle delay through checkpoint control that is sensitive to impaired kinetochore function. The BUB2 gene may be part of a separate checkpoint that responds to abnormal spindle structure.

scholarly journals Mammalian Orc1 Protein Is Selectively Released from Chromatin and Ubiquitinated during the S-to-M Transition in the Cell Division Cycle

2002 ◽  
Vol 22 (1) ◽  
pp. 105-116 ◽  
Author(s):  
Cong-Jun Li ◽  
Melvin L. DePamphilis
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Schizosaccharomyces Pombe ◽  
Half Life ◽  
S Phase ◽  
Cell Division Cycle ◽  
26S Proteasome ◽  
Selective Dissociation

ABSTRACT Previous studies have shown that changes in the affinity of the hamster Orc1 protein for chromatin during the M-to-G1 transition correlate with the activity of hamster origin recognition complexes (ORCs) and the appearance of prereplication complexes at specific sites. Here we show that Orc1 is selectively released from chromatin as cells enter S phase, converted into a mono- or diubiquitinated form, and then deubiquitinated and re-bound to chromatin during the M-to-G1 transition. Orc1 is degraded by the 26S proteasome only when released into the cytosol, and peptide additions to Orc1 make it hypersensitive to polyubiquitination. In contrast, Orc2 remains tightly bound to chromatin throughout the cell cycle and is not a substrate for ubiquitination. Since the concentration of Orc1 remains constant throughout the cell cycle, and its half-life in vivo is the same as that of Orc2, ubiquitination of non-chromatin-bound Orc1 presumably facilitates the inactivation of ORCs by sequestering Orc1 during S phase. Thus, in contrast to yeast (Saccharomyces cerevisiae and Schizosaccharomyces pombe), mammalian ORC activity appears to be regulated during each cell cycle through selective dissociation and reassociation of Orc1 from chromatin-bound ORCs.

Cell cycle arrest caused by CLN gene deficiency in Saccharomyces cerevisiae resembles START-I arrest and is independent of the mating-pheromone signalling pathway

1990 ◽  
Vol 10 (12) ◽  
pp. 6482-6490
Author(s):  
F R Cross
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cell Division ◽  
Cell Cycle Arrest ◽  
S Phase ◽  
Signalling Pathway ◽  
Phase Cell ◽  
Glucose Medium ◽  
Coding Sequence ◽  
Cycle Arrest

Null mutations in three genes encoding cyclin-like proteins (CLN1, CLN2, and CLN3) in Saccharomyces cerevisiae cause cell cycle arrest in G1 (cln arrest). In cln1 cln2 cln3 strains bearing plasmids containing the CLN3 (also called WHI1 or DAF1) coding sequence under the transcriptional control of a galactose-regulated promoter, shift from galactose to glucose medium (shutting off synthesis of CLN3 mRNA) allowed completion of cell cycles in progress but caused arrest in the ensuing unbudded G1 phase. Cell growth was not inhibited in arrested cells. Cell division occurred in glucose medium even if cells were arrested in S phase during the initial 2 h of glucose treatment, suggesting that CLN function may not be required in the cell cycle after S phase. However, when the coding sequence of the hyperactive C-terminal truncation allele CLN3-2 (formerly DAF1-1) was placed under GAL control, cells went through multiple cycles before arresting after a shift from galactose to glucose. These results suggest that the C terminus of the wild-type protein confers functional instability. cln-arrested cells are mating competent. However, cln arrest is distinct from constitutive activation of the mating-factor signalling pathway because cln-arrested cells were dependent on the addition of pheromone both for mating and for induction of an alpha-factor-induced transcript, FUS1, and because MATa/MAT alpha (pheromone-nonresponsive) strains were capable of cln arrest in G1 (although a residual capacity for cell division before arrest was observed in MATa/MAT alpha strains). These results are consistent with a specific CLN requirement for START transit.

scholarly journals EGT2 gene transcription is induced predominantly by Swi5 in early G1.

1996 ◽  
Vol 16 (7) ◽  
pp. 3264-3274 ◽  
Author(s):  
B Kovacech ◽  
K Nasmyth ◽  
T Schuster
Keyword(s):  
Cell Cycle ◽  
Transcriptional Activation ◽  
Cell Separation ◽  
S Phase ◽  
Dependent Manner ◽  
Yeast Saccharomyces Cerevisiae ◽  
Concentration Dependent Manner ◽  
A Cell ◽  
Cycle Dependent ◽  
Ho Gene

In a screen for cell cycle-regulated genes in the yeast Saccharomyces cerevisiae, we have identified a gene, EGT2, which is involved in cell separation in the G1 stage of the cell cycle. Transcription of EGT2 is tightly regulated in a cell cycle-dependent manner. Transcriptional levels peak at the boundary of mitosis and early G1 The transcription factors responsible for EGT2 expression in early G1 are Swi5 and, to a lesser extent, Ace2. Swi5 is involved in the transcriptional activation of the HO gene during late G1 and early S phase, and Ace2 induces CTS1 transcription during early and late G1 We show that Swi5 activates EGT2 transcription as soon as it enters the nucleus at the end of mitosis in a concentration-dependent manner. Since Swi5 is unstable in the nucleus, its level drops rapidly, causing termination of EGT2 transcription before cells are committed to the next cell cycle. However, Swi5 is still able to activate transcription of HO in late G1 in conjunction with additional activators such as Swi4 and Swi6.

scholarly journals The Ubp15 deubiquitinase promotes timely entry into S phase in Saccharomyces cerevisiae

2015 ◽  
Vol 26 (12) ◽  
pp. 2205-2216 ◽  
Author(s):  
Denis Ostapenko ◽  
Janet L. Burton ◽  
Mark J. Solomon
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Physiological Role ◽  
S Phase ◽  
G1 Phase ◽  
Deubiquitinating Enzyme ◽  
Anaphase Promoting Complex ◽  
Synthesis Inhibitor ◽  
Yeast Saccharomyces Cerevisiae ◽  
Increased Sensitivity

The anaphase-promoting complex in partnership with its activator, Cdh1, is an E3 ubiquitin ligase responsible for targeting cell cycle proteins during G1 phase. In the budding yeast Saccharomyces cerevisiae, Cdh1 associates with the deubiquitinating enzyme Ubp15, but the significance of this interaction is unclear. To better understand the physiological role(s) of Ubp15, we examined cell cycle phenotypes of cells lacking Ubp15. We found that ubp15∆ cells exhibited delayed progression from G1 into S phase and increased sensitivity to the DNA synthesis inhibitor hydroxyurea. Both phenotypes of ubp15∆ cells were rescued by additional copies of the S-phase cyclin gene CLB5. Clb5 is an unstable protein targeted for proteasome-mediated degradation by several pathways. We found that during G1 phase, the APCCdh1-mediated degradation of Clb5 was accelerated in ubp15∆ cells. Ubp15 interacted with Clb5 independent of Cdh1 and deubiquitinated Clb5 in a reconstituted system. Thus deubiquitination by Ubp15 counteracts APC activity toward cyclin Clb5 to allow Clb5 accumulation and a timely entry into S phase.

scholarly journals Segregation of unreplicated chromosomes in Saccharomyces cerevisiae reveals a novel G1/M-phase checkpoint.

1995 ◽  
Vol 15 (10) ◽  
pp. 5312-5321 ◽  
Author(s):  
J H Toyn ◽  
A L Johnson ◽  
L H Johnston
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Nuclear Division ◽  
Strain Differences ◽  
Mitotic Checkpoint ◽  
S Phase ◽  
Relative Timing ◽  
Checkpoint Pathway ◽  
M Phase ◽  
Normal Mitosis

Saccharomyces cerevisiae dbf4 and cdc7 cell cycle mutants block initiation of DNA synthesis (i.e., are iDS mutants) at 37 degrees C and arrest the cell cycle with a 1C DNA content. Surprisingly, certain dbf4 and cdc7 strains divide their chromatin at 37 degrees C. We found that the activation of the Cdc28 mitotic protein kinase and the Dbf2 kinase occurred with the correct relative timing with respect to each other and the observed division of the unreplicated chromatin. Furthermore, the division of unreplicated chromatin depended on a functional spindle. Therefore, the observed nuclear division resembled a normal mitosis, suggesting that S. cerevisiae commits to M phase in late G1 independently of S phase. Genetic analysis of dbf4 and cdc7 strains showed that the ability to restrain mitosis during a late G1 block depended on the genetic background of the strain concerned, since the dbf4 and cdc7 alleles examined showed the expected mitotic restraint in other backgrounds. This restraint was genetically dominant to lack of restraint, indicating that an active arrest mechanism, or checkpoint, was involved. However, none of the previously described mitotic checkpoint pathways were defective in the iDS strains that carry out mitosis without replicated DNA, therefore indicating that the checkpoint pathway that arrests mitosis in iDS mutants is novel. Thus, spontaneous strain differences have revealed that S. cerevisiae commits itself to mitosis in late G1 independently of entry into S phase and that a novel checkpoint mechanism can restrain mitosis if cells are blocked in late G1. We refer to this as the G1/M-phase checkpoint since it acts in G1 to restrain mitosis.

scholarly journals Cell cycle phase expansion in nitrogen-limited cultures of Saccharomyces cerevisiae.

1980 ◽  
Vol 85 (1) ◽  
pp. 96-107 ◽  
Author(s):  
C J Rivin ◽  
W L Fangman
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Cell Cycle ◽  
Cycle Length ◽  
Time Lapse ◽  
S Phase ◽  
Cycle Phase ◽  
Yeast Saccharomyces Cerevisiae ◽  
Bud Emergence ◽  
Length Changes ◽  
Cell Cycle Length

The time and coordination of cell cycle events were examined in the budding yeast Saccharomyces cerevisiae. Whole-cell autoradiographic techniques and time-lapse photography were used to measure the duration of the S, G1, and G2 phases, and the cell cycle positions of "start" and bud emergence, in cells whose growth rates were determined by the source of nitrogen. It was observed that the G1, S, and G2 phases underwent a proportional expansion with increasing cell cycle length, with the S phase occupying the middle half of the cell cycle. In each growth condition, start appeared to correspond to the G1 phase/S phase boundary. Bud emergence did not occur until mid S phase. These results show that the rate of transit through all phases of the cell cycle can vary considerably when cell cycle length changes. When cells growing at different rates were arrested in G1, the following synchronous S phase were of the duration expected from the length of S in each asynchronous population. Cells transferred from a poor nitrogen source to a good one after arrest in G1 went through the subsequent S phase at a rate characteristic of the better medium, indicating that cells are not committed in G1 to an S phase of a particular duration.

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