scholarly journals Mitotic control in the absence of cdc25 mitotic inducer in fission yeast

1999 ◽  
Vol 112 (7) ◽  
pp. 1085-1092 ◽  
Author(s):  
A. Sveiczer ◽  
B. Novak ◽  
J.M. Mitchison
Keyword(s):  
Fission Yeast ◽  
Size Control ◽  
Yeast Cells ◽  
Early Event ◽  
Wild Type ◽  
Rate Limiting Step ◽  
Minimal Cycle ◽  
Novel Method ◽  
Successive Generations ◽  
Rate Limiting

Fission yeast cells tolerate the total absence of the cdc25 mitotic inducer in two cases, either in cdc2-3w or in wee1 genetic backgrounds. In the cdc2-3w cdc25Delta double mutant, the rate-limiting step leading to mitosis is reaching a critical size. However, the size control of this mutant operates in late G2, which is different from wild-type (WT) cells. This fact suggests that in WT the rate-limiting molecular process during the G2 timer is the Tyr15 dephosphorylation of cdc2, for which the cdc25 phosphatase (together with its back-up, pyp3) is dependent. In the wee1-50 cdc25Delta mutant, the population splits into different clusters, all lacking mitotic size control. This strain maintains size homeostasis by a novel method, which is random movement of the cells from one cluster to another in the successive generations. These cells should normally have a ‘minimal cycle’, a ‘timer’ with short G1 and G2 phases. However, very often the cells abort mitosis, possibly at an early event and return back to early G2, thus lengthening their cycles. The inability of these cells to start anaphase might be caused by the absence of the main mitotic regulators (wee1 and cdc25) and the improper regulation of their back-up copies (mik1 and pyp3, respectively).

scholarly journals Amino acids whose intracellular levels change most during aging alter chronological lifespan of fission yeast

2020 ◽  
Author(s):  
Charalampos Rallis ◽  
Michael Mülleder ◽  
Graeme Smith ◽  
Yan Zi Au ◽  
Markus Ralser ◽  
...  
Keyword(s):  
Amino Acids ◽  
Amino Acid ◽  
Fission Yeast ◽  
Yeast Cells ◽  
Total Amino Acid ◽  
Wild Type ◽  
Chronological Lifespan ◽  
Biomarkers Of Aging ◽  
Concentration Changes ◽  
Amino Acid Levels

AbstractAmino acid deprivation or supplementation can affect cellular and organismal lifespan, but we know little about the role of concentration changes in free, intracellular amino acids during aging. Here, we determine free amino-acid levels during chronological aging of non-dividing fission yeast cells. We compare wild-type with long-lived mutant cells that lack the Pka1 protein of the protein kinase A signalling pathway. In wild-type cells, total amino-acid levels decrease during aging, but much less so in pka1 mutants. Two amino acids strongly change as a function of age: glutamine decreases, especially in wild-type cells, while aspartate increases, especially in pka1 mutants. Supplementation of glutamine is sufficient to extend the chronological lifespan of wild-type but not of pka1Δ cells. Supplementation of aspartate, on the other hand, shortens the lifespan of pka1Δ but not of wild-type cells. Our results raise the possibility that certain amino acids are biomarkers of aging, and their concentrations during aging can promote or limit cellular lifespan.

scholarly journals The Proteomic Analysis of Maize Endosperm Protein Enriched by Phos-tagtm Reveals the Phosphorylation of Brittle-2 Subunit of ADP-Glc Pyrophosphorylase in Starch Biosynthesis Process

2019 ◽  
Vol 20 (4) ◽  
pp. 986 ◽  
Author(s):  
Guowu Yu ◽  
Yanan Lv ◽  
Leiyang Shen ◽  
Yongbin Wang ◽  
Yun Qing ◽  
...  
Keyword(s):  
Starch Biosynthesis ◽  
Maize Starch ◽  
Maize Endosperm ◽  
Phosphorylated Proteins ◽  
Agarose Beads ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Endosperm Protein ◽  
Novel Method ◽  
Rate Limiting

AGPase catalyzes a key rate-limiting step that converts ATP and Glc-1-p into ADP-glucose and diphosphate in maize starch biosynthesis. Previous studies suggest that AGPase is modulated by redox, thermal and allosteric regulation. However, the phosphorylation of AGPase is unclear in the kernel starch biosynthesis process. Phos-tagTM technology is a novel method using phos-tagTM agarose beads for separation, purification, and detection of phosphorylated proteins. Here we identified phos-tagTM agarose binding proteins from maize endosperm. Results showed a total of 1733 proteins identified from 10,678 distinct peptides. Interestingly, a total of 21 unique peptides for AGPase sub-unit Brittle-2 (Bt2) were identified. Bt2 was demonstrated by immunoblot when enriched maize endosperm protein with phos-tagTM agarose was in different pollination stages. In contrast, Bt2 would lose binding to phos-tagTM when samples were treated with alkaline phosphatase (ALP). Furthermore, Bt2 could be detected by Pro-Q diamond staining specifically for phosphorylated protein. We further identified the phosphorylation sites of Bt2 at Ser10, Thr451, and Thr462 by iTRAQ. In addition, dephosphorylation of Bt2 decreased the activity of AGPase in the native gel assay through ALP treatment. Taking together, these results strongly suggest that the phosphorylation of AGPase may be a new model to regulate AGPase activity in the starch biosynthesis process.

Strongly oversized fission yeast cells lack any size control and tend to grow linearly rather than bilinearly

Yeast ◽  
2020 ◽  
Author(s):  
Zsófia Nagy ◽  
Anna Medgyes‐Horváth ◽  
Eszter Vörös ◽  
Ákos Sveiczer
Keyword(s):  
Fission Yeast ◽  
Size Control ◽  
Yeast Cells

scholarly journals A Positive Role for Rhizobitoxine in Rhizobium-legume Symbiosis

1999 ◽  
Vol 12 (12) ◽  
pp. 1082-1089 ◽  
Author(s):  
Samuel Duodu ◽  
T. V. Bhuvaneswari ◽  
Thomas J. W. Stokkermans ◽  
N. Kent Peters
Keyword(s):  
Ethylene Biosynthesis ◽  
Nodule Development ◽  
Ethylene Inhibitors ◽  
Wild Type ◽  
Positive Role ◽  
Rate Limiting Step ◽  
Mutant Strains ◽  
Legume Symbiosis ◽  
Exogenous Ethylene ◽  
Rate Limiting

Although Bradyrhizobium elkanii is a mutualistic symbiont of legumes, it synthesizes a phytotoxin, rhizobitoxine, that causes chlorosis on a variety of legume hosts, giving a pathogenic character to these interactions. No positive role for rhizobitoxine has been previously demonstrated. Interestingly, rhizobitoxine inhibits the rate-limiting step for ethylene biosynthesis, a plant hormone known to inhibit or down-regulate nodule development. We hypothesized that rhizobitoxine plays a positive role in nodule development through its inhibition of ethylene biosynthesis. To test this hypothesis, host plants of B. elkanii were screened for a differential nodulation response to the wild-type and rhizobitoxine mutant strains. In Vigna radiata (mungbean), the rhizobitoxine mutant strains induced many aborted nodules arrested at all stages of pre-emergent and post-emergent development and formed significantly fewer mature nodules than the wild type. Experiments revealed that nodulation of mungbean plants is sensitive to exogenous ethylene, and that the ethylene inhibitors aminoethoxyvinylglycine and Co2+ were able to partially restore a wild-type nodulation pattern to the rhizobitoxine mutants. This is the first demonstration of a nodulation phenotype of the rhizobitoxine mutants and suggests that rhizobitoxine plays a positive and necessary role in Rhizobium-legume symbiosis through its inhibition of ethylene biosynthesis.

scholarly journals The number of cytokinesis nodes in mitotic fission yeast scales with cell volume

2021 ◽  
Author(s):  
Wasim A Sayyad ◽  
Thomas D Pollard
Keyword(s):  
Plasma Membrane ◽  
Fission Yeast ◽  
Large Population ◽  
Yeast Cells ◽  
Wild Type ◽  
Contractile Ring ◽  
Node Number ◽  
Nmt1 Promoter ◽  
Wide Range ◽  
Mutant Cells

Cytokinesis nodes are assemblies of stoichiometric ratios of proteins associated with the plasma membrane, which serve as precursors for the contractile ring during cytokinesis by fission yeast. The total number of nodes is uncertain, because of the limitations of the methods used previously. Here we used the ~140 nm resolution of Airyscan confocal microscopy to resolve a large population of dim, unitary cytokinesis nodes in 3D reconstructions of whole fission yeast cells. Wild-type fission yeast cells make about 200 unitary cytokinesis nodes. Most, but not all of these nodes condense into a contractile ring. The number of cytokinesis nodes scales with cell size in four strains tested, although wide rga4Δ mutant cells form somewhat fewer cytokinesis nodes than expected from the overall trend. The surface density of Pom1 kinase on the plasma membrane around the equators of cells is similar with a wide range of node numbers, so Pom1 does not control cytokinesis node number. However, varying protein concentrations with the nmt1 promoter showed that the numbers of nodes increase above a baseline of about 200 with the total cellular concentration of either Pom1 or the kinase Cdr2.

The size control of fission yeast revisited

1996 ◽  
Vol 109 (12) ◽  
pp. 2947-2957 ◽  
Author(s):  
A. Sveiczer ◽  
B. Novak ◽  
J.M. Mitchison
Keyword(s):  
Fission Yeast ◽  
Kinase Activity ◽  
Size Control ◽  
Time Lapse ◽  
Critical Threshold ◽  
Wild Type ◽  
Linear Rate ◽  
Cycle Times ◽  
Threshold Size ◽  
Histone Kinase

An analysis was made of cell length and cycle time in time-lapse films of the fission yeast Schizosaccharomyces pombe using wild-type (WT) cells and those of various mutants. The more important conclusions about ‘size controls’ are: (1) there is a marker in G2 in WT cells provided by a rate change point (RCP) where the linear rate of length growth increases by approximately 30%. The period before this RCP is dependent on size and can be called a ‘sizer’. The period after the RCP is nearly independent of size and can be called a ‘timer’. The achievement of a critical threshold size is at or near the RCP which is on average at about 0.3 of the cycle (halfway through G2). This is much earlier than was previously believed. (2) The RCP is at about the time when H1 histone kinase activity and the B type cyclin cdc13 start to rise in preparation for mitosis. The RCP is also associated with other metabolic changes. (3) In wee1 mutants, the mitotic size control is replaced by a G1/S size control which is as strong as the mitotic control. As in WT cells, there is a sizer which precedes the RCP followed by a timer but the RCP is at about the G1/S boundary and has a larger increase (approximately 100%) in rate. (4) cdc25 is not an essential part of the size control at mitosis or at the G1/S boundary. (5) Three further situations have been examined in which the mitotic size control has been abolished. First, induction synchronisation by block and release of cdc2 and cdc10. In the largest oversize-cells which are produced, the RCP is pushed back to the beginning of the cycle. There is no sizer period but only a timer. Second, when both the antagonists wee1 and cdc25 are absent in the double mutant wee1-50 cdc25 delta. In this interesting situation there is apparently no mitotic size control and the cycle times are quantised. Third, in rum1 delta wee1-50 where the normal long G1 in wee1 is much reduced, there is probably no size control either in G1 or in G2 causing a continuous shortening of division length from cycle to cycle.

Three factors that modulate the activity of class D β-lactamases and interfere with the post-translational carboxylation of Lys70

2010 ◽  
Vol 432 (3) ◽  
pp. 495-506 ◽  
Author(s):  
Lionel Vercheval ◽  
Cédric Bauvois ◽  
Alexandre di Paolo ◽  
Franck Borel ◽  
Jean-Luc Ferrer ◽  
...  
Keyword(s):  
Active Site ◽  
Chloride Ions ◽  
Side Chain ◽  
Wild Type ◽  
Post Translational Modification ◽  
Rate Limiting Step ◽  
Class D ◽  
The Individual ◽  
Rate Limiting

The activity of class D β-lactamases is dependent on Lys70 carboxylation in the active site. Structural, kinetic and affinity studies show that this post-translational modification can be affected by the presence of a poor substrate such as moxalactam but also by the V117T substitution. Val117 is a strictly conserved hydrophobic residue located in the active site. In addition, inhibition of class D β-lactamases by chloride ions is due to a competition between the side chain carboxylate of the modified Lys70 and chloride ions. Determination of the individual kinetic constants shows that the deacylation of the acyl–enzyme is the rate-limiting step for the wild-type OXA-10 β-lactamase.

scholarly journals The size-wise nucleus: nuclear volume control in eukaryotes

2007 ◽  
Vol 179 (4) ◽  
pp. 583-584 ◽  
Author(s):  
Michael D. Huber ◽  
Larry Gerace
Keyword(s):  
Fission Yeast ◽  
Cell Size ◽  
Size Control ◽  
Growth Conditions ◽  
Nuclear Size ◽  
Yeast Cells ◽  
Volume Control ◽  
Wide Range ◽  
The Relationship

Eukaryotic cells have an “awareness” of their volume and organellar volumes, and maintain a nuclear size that is proportional to the total cell size. New studies in budding and fission yeast have examined the relationship between cell and nuclear volumes. It was found that the size of the nucleus remains proportional to cell size in a wide range of genetic backgrounds and growth conditions that alter cell volume and DNA content. Moreover, in multinucleated fission yeast cells, Neumann and Nurse (see p. 593 of this issue) found that the sizes of individual nuclei are controlled by the relative amount of cytoplasm surrounding each nucleus. These results highlight a role of the cytoplasm in nuclear size control.

scholarly journals Mutations in VPS16 and MRT1Stabilize mRNAs by Activating an Inhibitor of the Decapping Enzyme

1999 ◽  
Vol 19 (11) ◽  
pp. 7568-7576 ◽  
Author(s):  
Shuang Zhang ◽  
Carol J. Williams ◽  
Kevin Hagan ◽  
Stuart W. Peltz
Keyword(s):  
Rna Stability ◽  
Wild Type ◽  
Mrna Decapping ◽  
Hsp70 Family ◽  
Rate Limiting Step ◽  
Nonsense Codon ◽  
Decapping Enzyme ◽  
Rate Limiting

ABSTRACT Decapping is a rate-limiting step in the decay of many yeast mRNAs; the activity of the decapping enzyme therefore plays a significant role in determining RNA stability. Using an in vitro decapping assay, we have identified a factor, Vps16p, that regulates the activity of the yeast decapping enzyme, Dcp1p. Mutations in the VPS16 gene result in a reduction of decapping activity in vitro and in the stabilization of both wild-type and nonsense-codon-containing mRNAs in vivo. The mrt1-3 allele, previously shown to affect the turnover of wild-type mRNAs, results in a similar in vitro phenotype. Extracts from both vps16 and mrt1 mutant strains inhibit the activity of purified Flag-Dcp1p. We have identified a 70-kDa protein which copurifies with Flag-Dcp1p as the abundant Hsp70 family member Ssa1p/2p. Intriguingly, the interaction with Ssa1p/2p is enhanced in strains with mutations in vps16 ormrt1. We propose that Hsp70s may be involved in the regulation of mRNA decapping.

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