Myosin
Dennis Bray in Cell Movements, 2000
This chapter describes the structure and motile properties of myosin II, which drives muscle contraction, as well as numerous contractile processes in nonmuscle cells. It examines the families of 'unconventional' myosins, which come in a rich variety of shapes and sizes and have often unexpected functions. The chapter highlights the importance of recombinant DNA studies and genetics in analysis of the cytoskeleton. It examines that myosin II molecules assemble into bipolar filaments that can cause actin filaments to contract if supplied with ATP. The chapter discusses that mutants of Dictyostelium lacking the gene for myosin II can perform cytokinesis, although their efficiency is impaired. It seems that in its most generic form, animal cell division is driven by a flow of actin from the opposing poles toward center of the cell, driven by regional differences in actin assembly and disruption. Both Acanthamoeba and Dictyostelium have multiple myosin I genes, which gene knockout studies suggest act in concert or have overlapping functions.
The Kinesin-6 Family
Claire T. Friel in The Kinesin Superfamily Handbook, 2020
The Kinesin-6 family are N-terminal motor domain kinesins. Available data suggests that they are plus-end-directed translocating motors. The motor domain is followed by a region of predicted coiled-coil, followed by a C-terminal tail domain. The coiled-coil region mediates the interaction with various binding partners and is likely responsible for multimerisation. A common theme in the physiological role of the Kinesin-6 family is their involvement in cell division. Members of this family play a crucial role in regulation of cytokinesis. The activity of several Kinesin-6 family members is regulated by phosphorylation. KIF20A requires phosphorylation by PLK1 to allow completion of cytokinesis. The interaction of Klp9 and its interacting partner Ase1 is regulated via phosphorylation, with dephosphorylation of both proteins promoting their interaction and resulting in enhanced velocity of spindle elongation.
CELL
Hugh Fletcher, Ivor Hickey, Paul Winter, Paul Winter in BIOS Instant Notes in Genetics, 2002
The progression from one cell division to the next can be regarded as a cyclic process, the cell cycle. During this time the cell must replicate its contents and then organize the distribution of its components equally between two daughter cells. Except in the production of gametes (see Section C3) the nuclei of eukaryote cells divide by mitosis and in parallel with this the cytoplasm divides by cytokinesis. These processes are easily visualized in fixed or living cells. The period between two consecutive divisions is referred to as a cell cycle. The replication of DNA is accomplished during a period in the cell cycle known as the synthetic or S phase. The period preceding S phase is called G1 (gap 1), and the period between S phase and division is known as G2 (gap 2).
Cytokinesis in Drosophila male meiosis
Published in Spermatogenesis, 2012
Maria Grazia Giansanti, Stefano Sechi, Anna Frappaolo, Giorgio Belloni, Roberto Piergentili
Cytokinesis separates the cytoplasm and the duplicated genome into two daughter cells at the end of cell division. This process must be finely regulated to maintain ploidy and prevent tumor formation. Drosophila male meiosis provides an excellent cell system for investigating cytokinesis. Mutants affecting this process can be easily identified and spermatocytes are large cells particularly suitable for cytological analysis of cytokinetic structures. Over the past decade, the powerful tools of Drosophila genetics and the unique characteristics of this cell system have led researchers to identify molecular players of the cell cleavage machinery and to address important open questions. Although spermatocyte cytokinesis is incomplete, resulting in formation of stable intercellular bridges, the molecular mechanisms are largely conserved in somatic cells. Thus, studies of Drosophila male meiosis will shed new light on the complex cell circuits regulating furrow ingression and substantially further our knowledge of cancer and other human diseases.
Assessment of the genotoxic potential of a migraine-specific drug by comet and cytokinesis-block micronucleus assays
Published in Expert Opinion on Drug Metabolism & Toxicology, 2020
Akin Cayir, Hayal Cobanoglu, Munevver Coskun
Background: Eletriptan is a migraine-specific drug-containing the triptan group. In terms of drug safety, the present study aimed to investigate the genotoxic potential of eletriptan. Research design & methods: We conducted our study by using the cytokinesis-block micronucleus cytome (CBMN) assay, a comprehensive method for measuring micronucleus formation, and a sensitive method for detecting DNA-strand breaks. In the assay, cytokinesis-block proliferation index and the frequency of micronuclei were evaluated in lymphocytes treated with three different concentrations (1, 10 and 25 µg/ml) of eletriptan for 48 hours. In comet assays, DNA damage was evaluated in leucocytes treated with three different concentrations (1, 10 and 25 µg/ml) of eletriptan for an hour. Results: Eletriptan did not induce cytotoxicity nor any increased micronuclei frequencies. While the comet parameters % DNA in tail, tail moment, and the olive moment was found to be significantly increased at 10 and 25 µg/ml, the cytokinesis-block proliferation index values were not. Conclusion: These findings suggest that eletriptan is non-cytotoxic but potentially weakly genotoxic at higher concentrations (10 and 25 µg/ml).
Inorganic tin compounds do not induce micronuclei in human lymphocytes in the absence of metabolic activation
Published in Drug and Chemical Toxicology, 2014
Artemis Damati, Dimitris Vlastos, Athanassios I. Philippopoulos, Demetrios P. Matthopoulos
The genotoxic evaluation (in vitro analysis) of a series of eight inorganic tin(II) and tin(IV) compounds [tin(II) acetate, tin(II) chloride, tin(II) ethylhexanoate, tin(II) oxalate, tin(II) oxide, tin(IV) acetate, tin(IV) chloride and tin(IV) oxide], for the detection of micronuclei in human blood lymphocytes, was performed in the absence of metabolic activation by the cytokinesis-block micronucleus assay. Human lymphocytes were treated for over one cell cycle (31 hours), with concentrations ranging from 1 to 75 μM (1, 5, 10, 20, 50 and 75 μM), of tin(II) and tin(IV) salts dissolved in dimethyl sulfoxide. The above-listed concentrations cover the values that have been detected in humans with no occupational exposure to tin compounds. The experimental results show the absence of genotoxicity for all inorganic compounds tested in the specific concentrations and experimental conditions. Cytotoxic effects of tin(II) and tin(IV) compounds were evaluated by the determination of cytokinesis block proliferation index and cytotoxicity percentage. Our observations on the cytotoxicity pattern of the tested tin(II) and tin(IV) compounds indicate that they are cytotoxic in several tested concentrations to human lymphocytes treated in vitro. The observed differences in cytotoxicity of each tested compound might reflect differences in their chemical structure.
Related Knowledge Centers
- Cell Division
- Cytoplasm
- Ovarian Follicle
- Ovum
- Cell Nucleus Division
- Cell
- Chromosome