scholarly journals Cell morphology and nucleoid dynamics in dividing D. radiodurans

2019 ◽  
Author(s):  
Kevin Floc’h ◽  
Françoise Lacroix ◽  
Pascale Servant ◽  
Yung-Sing Wong ◽  
Jean-Philippe Kleman ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Single Molecule ◽  
Cell Morphology ◽  
Cell Cycle Progression ◽  
Deinococcus Radiodurans ◽  
Morphological Changes ◽  
Cycle Progression ◽  
Chromosomal Arrangement ◽  
Tightly Coupled ◽  
Large Spherical

AbstractOur knowledge of bacterial nucleoids originates mostly from studies of rod- or crescent-shaped bacteria. Here, we reveal that Deinococcus radiodurans, a relatively large, spherical bacterium, possessing a multipartite genome, and well-known for its radioresistance, constitutes a valuable system for the study of nucleoids in cocci. Using advanced microscopy, we show that as D. radiodurans progresses through its cell cycle, it undergoes coordinated morphological changes at both the cellular and nucleoid level. D. radiodurans nucleoids were found to be highly condensed, but also surprisingly dynamic, adopting multiple distinct configurations and presenting a novel chromosomal arrangement in which oriC loci are radially distributed around clustered ter sites maintained at the centre of cells. Single-molecule and ensemble studies of the abundant histone-like HU protein suggest that its loose binding to DNA may contribute to this remarkable plasticity. These findings clearly demonstrate that nucleoid organization is complex and tightly coupled to cell cycle progression.

scholarly journals Differential Modulation and Subsequent Blockade of Mitogenic Signaling and Cell Cycle Progression by Pasteurella multocida Toxin

2000 ◽  
Vol 68 (8) ◽  
pp. 4531-4538 ◽  
Author(s):  
Brenda A. Wilson ◽  
Lyaylya R. Aminova ◽  
Virgilio G. Ponferrada ◽  
Mengfei Ho
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Pasteurella Multocida ◽  
Morphological Changes ◽  
Cell Types ◽  
Vero Cells ◽  
3T3 Cells ◽  
Mitogenic Response ◽  
Cycle Progression ◽  
Swiss 3T3

ABSTRACT The intracellularly acting protein toxin of Pasteurella multocida (PMT) causes numerous effects in cells, including activation of inositol 1,4,5-trisphosphate (IP3) signaling, Ca2+ mobilization, protein phosphorylation, morphological changes, and DNA synthesis. The direct intracellular target of PMT responsible for activation of the IP3 pathway is the Gq/11α-protein, which stimulates phospholipase C (PLC) β1. The relationship between PMT-mediated activation of the Gq/11-PLC-IP3pathway and its ability to promote mitogenesis and cellular proliferation is not clear. PMT stimulation of p42/p44 mitogen-activated protein kinase occurs upstream via Gq/11-dependent transactivation of the epidermal growth factor receptor. We have further characterized the effects of PMT on the downstream mitogenic response and cell cycle progression in Swiss 3T3 and Vero cells. PMT treatment caused dramatic morphological changes in both cell lines. In Vero cells, limited multinucleation, nuclear fragmentation, and disruption of cytokinesis were also observed; however, a strong mitogenic response occurred only with Swiss 3T3 cells. Significantly, this mitogenic response was not sustained. Cell cycle analysis revealed that after the initial mitogenic response to PMT, both cell types subsequently arrested primarily in G1and became unresponsive to further PMT treatment. In Swiss 3T3 cells, PMT induced up-regulation of c-Myc; cyclins D1, D2, D3, and E; p21; PCNA; and the Rb proteins, p107 and p130. In Vero cells, PMT failed to up-regulate PCNA and cyclins D3 and E. We also found that the initial PMT-mediated up-regulation of several of these signaling proteins was not sustained, supporting the subsequent cell cycle arrest. The consequences of PMT entry thus depend on the differential regulation of signaling pathways within different cell types.

Genetic and morphological evidence for two parallel pathways of cell-cycle-coupled cytokinesis inDictyostelium

2002 ◽  
Vol 115 (10) ◽  
pp. 2241-2251 ◽  
Author(s):  
Akira Nagasaki ◽  
Eugenio L. de Hostos ◽  
Taro Q. P. Uyeda
Keyword(s):  
Cell Cycle ◽  
Cell Cycle Progression ◽  
Morphological Changes ◽  
Mutant Cell ◽  
Myosin Ii ◽  
Morphological Evidence ◽  
Cleavage Furrow ◽  
Cycle Progression ◽  
Parallel Pathways ◽  
Substrate Adhesion

Myosin-II-null cells of Dictyostelium discoideum cannot divide in suspension, consistent with the dogma that myosin II drives constriction of the cleavage furrow and, consequently, cytokinesis (cytokinesis A). Nonetheless, when grown on substrates, these cells exhibit efficient,cell-cycle-coupled division, suggesting that they possess a novel,myosin-II-independent, adhesion-dependent method of cytokinesis (cytokinesis B). Here we show that double mutants lacking myosin II and either AmiA or coronin, both of which are implicated in cytokinesis B, are incapable of cell-cycle-coupled cytokinesis. These double mutants multiplied mainly by cytokinesis C, a third, inefficient, method of cell division, which requires substrate adhesion and is independent of cell cycle progression. In contrast,double mutants lacking AmiA and coronin were no sicker than each of the single mutants, indicating that the severe defects of myosin II-/AmiA- or myosin II-/coronin-mutants are not simple additive effects of two mutations. We take this as genetic evidence for two parallel pathways both of which lead to cell-cycle-coupled cytokinesis. This conclusion is supported by differences in morphological changes during cytokinesis in the mutant cell lines.

scholarly journals TORC2 dependent phosphorylation modulates calcium regulation of fission yeast myosin

2018 ◽  
Author(s):  
Karen Baker ◽  
Irene A. Gyamfi ◽  
Gregory I. Mashanov ◽  
Justin E. Molloy ◽  
Michael A. Geeves ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Growth ◽  
Fission Yeast ◽  
Single Molecule ◽  
Cell Cycle Progression ◽  
Neck Region ◽  
Dependent Manner ◽  
Meiotic Cell ◽  
Cycle Progression ◽  
Cellular Environment

AbstractAll cells have the ability to respond to changes in their environment. Signalling networks modulate cytoskeleton and membrane organisation to impact cell cycle progression, polarised cell growth and multicellular development according to the environmental setting. Using diverse in vitro, in vivo and single molecule techniques we have explored the role of myosin-1 signalling in regulating endocytosis during both mitotic and meiotic cell cycles. We have established that a conserved serine within the neck region of the sole fission yeast myosin-1 is phosphorylated in a TORC2 dependent manner to modulate myosin function. Myo1 neck phosphorylation brings about a change in the conformation of the neck region and modifies its interaction with calmodulins, Myo1 dynamics at endocytic foci, and promotes calcium dependent switching between different calmodulin light chains. These data provide insight into a novel mechanism by which myosin neck phosphorylation modulates acto-myosin dynamics to control polarised cell growth in response to mitotic and meiotic cell-cycle progression and the cellular environment.

scholarly journals DNA Ligase I Deficiency Leads to Replication-Dependent DNA Damage and Impacts Cell Morphology without Blocking Cell Cycle Progression

2009 ◽  
Vol 29 (8) ◽  
pp. 2032-2041 ◽  
Author(s):  
Samuela Soza ◽  
Valentina Leva ◽  
Riccardo Vago ◽  
Giovanni Ferrari ◽  
Giuliano Mazzini ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Dna Damage ◽  
Cell Morphology ◽  
Cell Cycle Progression ◽  
S Phase ◽  
Dna Ligase ◽  
Cycle Progression ◽  
Genetic Syndrome ◽  
Γh2ax Foci ◽  
Dna Ligase I

ABSTRACT 46BR.1G1 cells derive from a patient with a genetic syndrome characterized by drastically reduced replicative DNA ligase I (LigI) activity and delayed joining of Okazaki fragments. Here we show that the replication defect in 46BR.1G1 cells results in the accumulation of both single-stranded and double-stranded DNA breaks. This is accompanied by phosphorylation of the H2AX histone variant and the formation of γH2AX foci that mark damaged DNA. Single-cell analysis demonstrates that the number of γH2AX foci in LigI-defective cells fluctuates during the cell cycle: they form in S phase, persist in mitosis, and eventually diminish in G1 phase. Notably, replication-dependent DNA damage in 46BR.1G1 cells only moderately delays cell cycle progression and does not activate the S-phase-specific ATR/Chk1 checkpoint pathway that also monitors the execution of mitosis. In contrast, the ATM/Chk2 pathway is activated. The phenotype of 46BR.1G1 cells is efficiently corrected by the wild-type LigI but is worsened by a LigI mutant that mimics the hyperphosphorylated enzyme in M phase. Notably, the expression of the phosphomimetic mutant drastically affects cell morphology and the organization of the cytoskeleton, unveiling an unexpected link between endogenous DNA damage and the structural organization of the cell.

Protein SUMOylation is Involved in Cell-cycle Progression and Cell Morphology in Giardia lamblia

2016 ◽  
Vol 64 (4) ◽  
pp. 491-503 ◽  
Author(s):  
Bruno M. Di Genova ◽  
Richard C. da Silva ◽  
Júlia P.C. da Cunha ◽  
Pablo R. Gargantini ◽  
Renato A. Mortara ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Morphology ◽  
Giardia Lamblia ◽  
Cell Cycle Progression ◽  
Cycle Progression ◽  
Protein Sumoylation

scholarly journals Inhibition of cell proliferation by the Mad1 transcriptional repressor.

1996 ◽  
Vol 16 (6) ◽  
pp. 2796-2801 ◽  
Author(s):  
M F Roussel ◽  
R A Ashmun ◽  
C J Sherr ◽  
R N Eisenman ◽  
D E Ayer
Keyword(s):  
Cell Cycle ◽  
Dna Sequences ◽  
Cell Cycle Progression ◽  
Leucine Zipper ◽  
Ectopic Expression ◽  
Transcriptional Repressor ◽  
Cell Types ◽  
3T3 Cells ◽  
Cycle Progression ◽  
Tightly Coupled

Mad1 is a basic helix-loop-helix-leucine zipper protein that is induced upon differentiation of a number of distinct cell types. Mad1 dimerizes with Max and recognizes the same DNA sequences as do Myc:Max dimers. However, Mad1 and Myc appear to have opposing functions. Myc:Max heterodimers activate transcription while Mad:Max heterodimers repress transcription from the same promoter. In addition Mad1 has been shown to block the oncogenic activity of Myc. Here we show that ectopic expression of Mad1 inhibits the proliferative response of 3T3 cells to signaling through the colony-stimulating factor-1 (CSF-1) receptor. The ability of over-expressed Myc and cyclin D1 to complement the mutant CSF-1 receptor Y809F (containing a Y-to-F mutation at position 809) is also inhibited by Mad1. Cell cycle analysis of proliferating 3T3 cells transfected with Mad1 demonstrates a significant decrease in the fraction of cells in the S and G2/M phases and a concomitant increase in the fraction of G1 phase cells, indicating that Mad1 negatively influences cell cycle progression from the G1 to the S phase. Mutations in Mad1 which inhibit its activity as a transcription repressor also result in loss of Mad1 cell cycle inhibitory activity. Thus, the ability of Mad1 to inhibit cell cycle progression is tightly coupled to its function as a transcriptional repressor.

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