THE G1 ARREST CAUSED BY NITROGEN STARVATION IN YEAST IS MEDIATED BY Cln CYCLIN DEGRADATION

1996 ◽  
Vol 24 (4) ◽  
pp. 515S-515S
Author(s):  
Carme Gallego ◽  
Neus Colomina ◽  
Eloi Gari ◽  
Enrique Herrero ◽  
Martí Aldea
Keyword(s):  
Nitrogen Starvation ◽  
G1 Arrest

scholarly journals Cig2, a B-type cyclin, promotes the onset of S in Schizosaccharomyces pombe.

1996 ◽  
Vol 16 (4) ◽  
pp. 1527-1533 ◽  
Author(s):  
O Mondesert ◽  
C H McGowan ◽  
P Russell
Keyword(s):  
Dna Replication ◽  
Schizosaccharomyces Pombe ◽  
Double Mutant ◽  
Kinase Activity ◽  
Nitrogen Starvation ◽  
Gradual Increase ◽  
S Phase ◽  
G1 Arrest ◽  
Cyclin Dependent Kinases ◽  
M Phase

Cdc2, a catalytic subunit of cyclin-dependent kinases, is required for both the G1-to-S and G2-to-M transitions in the fission yeast Schizosaccharomyces pombe. Cdc13, a B-type cyclin, is required for the M-phase induction function of Cd2. Two additional B-type cyclins, Cig1 and Cig2, have been identified in S. pombe, but none of the B-type cyclins are individually required for the onset of S. We report that Cdc13 is important for DNA replication in a strain lacking Cig2. Unlike deltacdc13 cells, double-mutant deltacdc13 deltacig2 cells are defective in undergoing multiple rounds of DNA replication. The conclusion that Cig2 promotes S is further supported by the finding that Cig2 protein and Cig2-associated kinase activity appear soon after the completion of M and peak during S, as well as the observation that S is delayed in deltacig2 cells as they recover from a G1 arrest induced by nitrogen starvation. These studies indicate that Cig2 is the primary S-phase-promoting cyclin in S. pombe but that Cdc13 can effectively substitute for Cig2 in deltacig2 cells. These observations also suggest that the gradual increase in the activity of Cdc2-Cdc13 kinase can be sufficient for the correct temporal ordering of S and M phases in deltacig2 cells.

Fission yeast TPR-family protein nuc2 is required for G1-arrest upon nitrogen starvation and is an inhibitor of septum formation

1995 ◽  
Vol 108 (3) ◽  
pp. 895-905 ◽  
Author(s):  
K. Kumada ◽  
S. Su ◽  
M. Yanagida ◽  
T. Toda
Keyword(s):  
Cell Cycle ◽  
Dna Replication ◽  
Fission Yeast ◽  
Nitrogen Starvation ◽  
G1 Arrest ◽  
Restrictive Temperature ◽  
Permissive Temperature ◽  
Septum Formation ◽  
Family Protein ◽  
Chromosome Separation

Fission yeast nuc2+ gene encodes a protein of a tetratricopeptide repeat (TPR) family which is conserved throughout evolution. We previously showed that nuc2 is required for exit from the mitotic metaphase. In this study, we present evidence which shows that nuc2 has two additional roles in the cell cycle. We showed that the nuc2 mutant is sterile even at the permissive temperature and septation occurs in the absence of chromosome separation at the restrictive temperature. The nuc2 mutant fails to arrest at the G1 phase upon nitrogen starvation at the permissive temperature which is a prerequisite for conjugation. Upon starvation, however, the nuc2 mutant ceased division normally and induced starvation-dependent gene expression. Therefore, the nuc2 mutant is deficient only for failure to block DNA replication upon starvation. At the lower restrictive temperature, the nuc2 mutant showed a ‘cut’ phenotype where septation and cytokinesis takes place without the completion of mitosis. Ectopic overexpression of the nuc2+ gene caused multiple rounds of S and M phases in the complete absence of septum formation. We propose that nuc2 is a novel cell cycle regulator essential for three events; firstly for exit from mitosis, secondly for DNA replication restraint under nutrient starvation and thirdly for inhibition of septation and cytokinesis until the completion of mitosis.

New Hybrid Scaffolds Based on Carbazole-Chalcones as Potent Anticancer Agents

2020 ◽  
Vol 20 ◽  
Author(s):  
Faisal Rashid ◽  
Sumera Zaib ◽  
Aliya Ibrar ◽  
Syeda Abida Ejaz ◽  
Aamer Saeed ◽  
...  
Keyword(s):  
Lactate Dehydrogenase ◽  
Hela Cells ◽  
Cervical Adenocarcinoma ◽  
G1 Arrest ◽  
Human Breast ◽  
Caspase 9 ◽  
Flow Cytometric ◽  
Pharmacodynamic Profile ◽  
Microscopic Studies ◽  
Mcf 7

Background and Objectives: Despite various technological advances for the treatment of cancer, the identification of new chemical entities with potent anticancer effects remain an indispensable requirement of the time due to multi-drug resistance exhibited by previously developed anticancer drugs. Particularly, the hybrid drugs incorporating two individual bioactive pharmacophores present medicinally important structural leads, thus improving the pharmacodynamic profile of the drug molecules. The antiproliferative and pro-apoptotic activity of the carbazole-chalcone hybrids on human breast and cervical cancer cells will be examined. Materials and Methods: To overcome such complications, in the current study, we evaluated the cytotoxic effects of carbazole-chalcone hybrids on human breast adenocarcinoma (MCF-7), cervical adenocarcinoma (HeLa) cells and normal cells i.e., baby hamster kidney cells (BHK-21) using MTT (dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide) assay. The mechanistic studies were performed on potent compound 4g by fluorescent microscopic studies, release of lactate dehydrogenase (LDH) and mitochondrial membrane potential, activation of caspase-9 and -3 and flow cytometric analysis. Results: As revealed by MTT assay, compound 4g was identified as the most potent derivative among the tested series with IC50 values of 5.64 and 29.15 μM against HeLa and MCF-7 cells, respectively. The results were compared with cisplatin. Fluorescent microscopic studies using 4′,6-diamidino-2-phenylindole (DAPI) and propidium iodide (PI) staining confirmed the occurrence of apoptosis in HeLa cells treated with the most active compound 4g. Moreover, compound 4g also triggered the release of lactate dehydrogenase (LDH) in treated HeLa and MCF-7 cells while a luminescence assay displayed a remarkable increase in the activity of caspase-9 and -3. Moreover, flow cytometric results revealed that compound 4g caused G0/G1 arrest in the treated HeLa cells. Conclusion: Our results demonstrated that the compound 4g possesses chemotherapeutic properties against breast cancer and cervical adenocarcinoma cells, thus warranting further research to test the anticancer efficacy of this compound at clinical level.

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