scholarly journals The 95F unconventional myosin is required for proper organization of the Drosophila syncytial blastoderm.

1995 ◽  
Vol 129 (6) ◽  
pp. 1575-1588 ◽  
Author(s):  
V Mermall ◽  
K G Miller
Keyword(s):  
Cell Cycle ◽  
Motor Activity ◽  
Actin Cytoskeleton ◽  
Three Dimensional ◽  
Nuclear Morphology ◽  
Unconventional Myosin ◽  
A Cell ◽  
Cytoskeletal Function ◽  
Cycle Dependent

The 95F myosin, a class VI unconventional myosin, associates with particles in the cytoplasm of the Drosophila syncytial blastoderm and is required for the ATP- and F-actin-dependent translocation of these particles. The particles undergo a cell cycle-dependent redistribution from domains that surround each nucleus in interphase to transient membrane invaginations that provide a barrier between adjacent spindles during mitosis. When 95F myosin function is inhibited by antibody injection, profound defects in syncytial blastoderm organization occur. This disorganization is seen as aberrant nuclear morphology and position and is suggestive of failures in cytoskeletal function. Nuclear defects correlate with gross defects in the actin cytoskeleton, including indistinct actin caps and furrows, missing actin structures, abnormal spacing of caps, and abnormally spaced furrows. Three-dimensional examination of embryos injected with anti-95F myosin antibody reveals that actin furrows do not invaginate as deeply into the embryo as do normal furrows. These furrows do not separate adjacent mitoses, since microtubules cross over them. These inappropriate microtubule interactions lead to aberrant nuclear divisions and to the nuclear defects observed. We propose that 95F myosin function is required to generate normal actin-based transient membrane furrows. The motor activity of 95F myosin itself and/or components within the particles transported to the furrows by 95F myosin may be required for normal furrows to form.

scholarly journals Truncated APC regulates the transcriptional activity of β-catenin in a cell cycle dependent manner

2006 ◽  
Vol 16 (2) ◽  
pp. 199-209 ◽  
Author(s):  
Jean Schneikert ◽  
Annette Grohmann ◽  
Jürgen Behrens
Keyword(s):  
Cell Cycle ◽  
Transcriptional Activity ◽  
Dependent Manner ◽  
A Cell ◽  
Cycle Dependent

scholarly journals Effects of cell-cycle-dependent expression on random fluctuations in protein levels

2016 ◽  
Vol 3 (12) ◽  
pp. 160578 ◽  
Author(s):  
Mohammad Soltani ◽  
Abhyudai Singh
Keyword(s):  
Cell Cycle ◽  
Cell Division ◽  
Protein Levels ◽  
Stochastic Component ◽  
Stochastic Expression ◽  
A Cell ◽  
Intrinsic Stochasticity ◽  
Cycle Dependent ◽  
Random Fluctuations ◽  
Cell To Cell Variability

Expression of many genes varies as a cell transitions through different cell-cycle stages. How coupling between stochastic expression and cell cycle impacts cell-to-cell variability (noise) in the level of protein is not well understood. We analyse a model where a stable protein is synthesized in random bursts, and the frequency with which bursts occur varies within the cell cycle. Formulae quantifying the extent of fluctuations in the protein copy number are derived and decomposed into components arising from the cell cycle and stochastic processes. The latter stochastic component represents contributions from bursty expression and errors incurred during partitioning of molecules between daughter cells. These formulae reveal an interesting trade-off: cell-cycle dependencies that amplify the noise contribution from bursty expression also attenuate the contribution from partitioning errors. We investigate the existence of optimum strategies for coupling expression to the cell cycle that minimize the stochastic component. Intriguingly, results show that a zero production rate throughout the cell cycle, with expression only occurring just before cell division, minimizes noise from bursty expression for a fixed mean protein level. By contrast, the optimal strategy in the case of partitioning errors is to make the protein just after cell division. We provide examples of regulatory proteins that are expressed only towards the end of the cell cycle, and argue that such strategies enhance robustness of cell-cycle decisions to the intrinsic stochasticity of gene expression.

scholarly journals Ser68 phosphoregulation is essential for CENP-A deposition, centromere function and viability in mice

2021 ◽  
Author(s):  
Yuting Liu ◽  
Kehui Wang ◽  
Li Huang ◽  
Jicheng Zhao ◽  
Xinpeng Chen ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Viability ◽  
Histone H3 ◽  
Dependent Manner ◽  
Centromere Function ◽  
Histone H3 Variant ◽  
A Cell ◽  
Cycle Dependent ◽  
Spatiotemporal Control

Centromere identity is defined by nucleosomes containing CENP-A, a histone H3 variant. The deposition of CENP-A at centromeres is tightly regulated in a cell-cycle-dependent manner. We previously reported that the spatiotemporal control of centromeric CENP-A incorporation is mediated by the phosphorylation of CENP-A Ser68. However, a recent report argued that Ser68 phosphoregulation is dispensable for accurate CENP-A loading. Here, we report that the substitution of Ser68 of endogenous CENP-A with either Gln68 or Glu68 severely impairs CENP-A deposition and cell viability. We also find that mice harboring the corresponding mutations are lethal. Together, these results indicate that the dynamic phosphorylation of Ser68 ensures cell-cycle-dependent CENP-A deposition and cell viability.

scholarly journals A Cell Cycle–Dependent Internal Ribosome Entry Site

2000 ◽  
Vol 5 (4) ◽  
pp. 607-616 ◽  
Author(s):  
Stéphane Pyronnet ◽  
Lucien Pradayrol ◽  
Nahum Sonenberg
Keyword(s):  
Cell Cycle ◽  
Internal Ribosome Entry Site ◽  
Entry Site ◽  
Internal Ribosome Entry ◽  
A Cell ◽  
Cycle Dependent

The SAC3 gene encodes a nuclear protein required for normal progression of mitosis

1996 ◽  
Vol 109 (6) ◽  
pp. 1575-1583
Author(s):  
A. Bauer ◽  
R. Kolling
Keyword(s):  
Cell Cycle ◽  
Actin Cytoskeleton ◽  
Nuclear Protein ◽  
Temperature Sensitive ◽  
Wild Type ◽  
Cell Cycle Delay ◽  
A Cell ◽  
Single Nucleus ◽  
Microtubule Function ◽  
Mitotic Defect

The SAC3 gene of Saccharomyces serevisiae has been implicated in actin function by genetic experiments showing that a temperature sensitive mutation in the essential actin gene (actl-1) can be suppressed by mutations in SAC3. An involvement of SAC3 in actin function is further suggested by the observation that the actin cytoskeleton is altered in SAC3 mutants. Our fractionation experiments, however, point to a nuclear localization of Sac3p. On sucrose density gradients Sac3p co-fractionated with the nuclear organelle markers examined. Furthermore, Sac3p was enriched 10-fold in a nuclei preparation along with the nuclear protein Nop1p. In this report we further show that SAC3 function is required for normal progression of mitosis. SAC3 mutants showed a higher fraction of large-budded cells in culture, indicative of a cell cycle delay. The predominant population among the large-budded sac3 cells were cells with a single nucleus at the bud-neck and a short intranuclear spindle. This suggests that a cell cycle delay occurs in mitosis prior to anaphase. The observation that SAC3 mutants lose chromosomes with higher frequency than wild-type is another indication for a mitotic defect in SAC3 mutants. We further noticed that SAC3 mutants are more resistant against the microtubule destabilizing drug benomyl. This finding suggests that SAC3 is involved, directly or indirectly, in microtubule function. In summary, our data indicate that SAC3 is involved in a process which affects both the actin cytoskeleton and mitosis.

Calcium/Calmodulin Affects Microtubule Stability in Lysed Protoplasts

1991 ◽  
Vol 100 (2) ◽  
pp. 311-317
Author(s):  
RICHARD J. CYR
Keyword(s):  
Cell Cycle ◽  
Dynamic Behavior ◽  
Growth And Development ◽  
Higher Plants ◽  
Plant Cells ◽  
Microtubule Stability ◽  
A Cell ◽  
Cycle Dependent ◽  
Carrot Protoplasts

Microtubules (Mts) are found in four distinct arrays appearing sequentially in a cell-cycle-dependent fashion within the cells of higher plants. Additionally, the cortical Mts of non-cycling cells are spatially altered in a variety of differentiated states. Information regarding the molecular details underlying these Mt-reorientation events in plant cells is scarce. Moreover, it is unclear how cytoskeletal behavior integrates with the myriad of other cellular activities that are altered concomitantly in both differentiating and cycling cells. Data are presented herein to indicate that calcium, in the form of a Ca2+/calmodulin complex, can alter the behavior of Mts in lysed carrot protoplasts. Mechanistically, we show that Ca2+/calmodulin most likely interacts with Mts via associations with microtubule associated pro- teins (MAPS). These results are discussed with reference to how Ca2+ may alter the dynamic behavior of Mts during growth and development.

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