Role of Cyclin B1/Cdc2 Up-Regulation in the Development of Mitotic Prometaphase Arrest in Human Breast Cancer Cells Treated with Nocodazole

Background: During a normal cell cycle, the transition from G 2 phase to mitotic phase is triggered by the activation of the cyclin B1-dependent Cdc2 kinase. Here we report our finding that treatment of MCF-7 human breast cancer cells with nocodazole, a prototypic microtubule inhibitor, results in strong up-regulation of cyclin B1 and Cdc2 levels, and their increases are required for the development of mitotic prometaphase arrest and characteristic phenotypes. Methodology/Principal Findings: It was observed that there was a time-dependent early increase in cyclin B1 and Cdc2 protein levels (peaking between 12 and 24 h post treatment), and their levels started to decline after the initial increase. This early up-regulation of cyclin B1 and Cdc2 closely matched in timing the nocodazole-induced mitotic prometaphase arrest. Selective knockdown of cyclin B1or Cdc2 each abrogated nocodazole-induced accumulation of prometaphase cells. The nocodazole-induced prometaphase arrest was also abrogated by pre-treatment of cells with roscovitine, an inhibitor of cyclin-dependent kinases, or with cycloheximide, a protein synthesis inhibitor that was found to suppress cyclin B1 and Cdc2 up-regulation. In addition, we found that MAD2 knockdown abrogated nocodazole-induced accumulation of cyclin B1 and Cdc2 proteins, which was accompanied by an attenuation of nocodazole-induced prometaphase arrest. Conclusions/Significance: These observations demonstrate that the strong early up-regulation of cyclin B1 and Cdc2 contributes critically to the rapid and selective accumulation of prometaphase-arrested cells, a phenomenon associate

Alpha-santalol, a chemopreventive agent against skin cancer, causes G2/M cell cycle arrest in both p53-mutated human epidermoid carcinoma A431 cells and p53 wild-type human melanoma UACC-62 cells

<p>Abstract</p> <p>Background</p> <p>α-Santalol, an active component of sandalwood oil, has shown chemopreventive effects on skin cancer in different murine models. However, effects of α-santalol on cell cycle have not been studied. Thus, the objective of this study was to investigate effects of α-santalol on cell cycle progression in both p53 mutated human epidermoid carcinoma A431 cells and p53 wild-type human melanoma UACC-62 cells to elucidate the mechanism(s) of action.</p> <p>Methods</p> <p>MTT assay was used to determine cell viability in A431 cells and UACC-62; fluorescence-activated cell sorting (FACS) analysis of propidium iodide staining was used for determining cell cycle distribution in A431 cells and UACC-62 cells; immunoblotting was used for determining the expression of various proteins and protein complexes involved in the cell cycle progression; siRNA were used to knockdown of p21 or p53 in A431 and UACC-62 cells and immunofluorescence microscopy was used to investigate microtubules in UACC-62 cells.</p> <p>Results</p> <p>α-Santalol at 50-100 μM decreased cell viability from 24 h treatment and α-santalol at 50 μM-75 μM induced G₂/M phase cell cycle arrest from 6 h treatment in both A431 and UACC-62 cells. α-Santalol altered expressions of cell cycle proteins such as cyclin A, cyclin B1, Cdc2, Cdc25c, p-Cdc25c and Cdk2. All of these proteins are critical for G₂/M transition. α-Santalol treatment up-regulated the expression of p21 and suppressed expressions of mutated p53 in A431 cells; whereas, α-santalol treatment increased expressions of wild-type p53 in UACC-62 cells. Knockdown of p21 in A431 cells, knockdown of p21 and p53 in UACC-62 cells did not affect cell cycle arrest caused by α-santalol. Furthermore, α-santalol caused depolymerization of microtubules similar to vinblastine in UACC-62 cells.</p> <p>Conclusions</p> <p>This study for the first time identifies effects of α-santalol in G₂/M phase arrest and describes detailed mechanisms of G₂/M phase arrest by this agent, which might be contributing to its overall cancer preventive efficacy in various mouse skin cancer models.</p

The dominant Anopheles vectors of human malaria in the Asia-Pacific region: occurrence data, distribution maps and bionomic précis

<p>Abstract</p> <p>Background</p> <p>The final article in a series of three publications examining the global distribution of 41 dominant vector species (DVS) of malaria is presented here. The first publication examined the DVS from the Americas, with the second covering those species present in Africa, Europe and the Middle East. Here we discuss the 19 DVS of the Asian-Pacific region. This region experiences a high diversity of vector species, many occurring sympatrically, which, combined with the occurrence of a high number of species complexes and suspected species complexes, and behavioural plasticity of many of these major vectors, adds a level of entomological complexity not comparable elsewhere globally. To try and untangle the intricacy of the vectors of this region and to increase the effectiveness of vector control interventions, an understanding of the contemporary distribution of each species, combined with a synthesis of the current knowledge of their behaviour and ecology is needed.</p> <p>Results</p> <p>Expert opinion (EO) range maps, created with the most up-to-date expert knowledge of each DVS distribution, were combined with a contemporary database of occurrence data and a suite of open access, environmental and climatic variables. Using the Boosted Regression Tree (BRT) modelling method, distribution maps of each DVS were produced. The occurrence data were abstracted from the formal, published literature, plus other relevant sources, resulting in the collation of DVS occurrence at 10116 locations across 31 countries, of which 8853 were successfully geo-referenced and 7430 were resolved to spatial areas that could be included in the BRT model. A detailed summary of the information on the bionomics of each species and species complex is also presented.</p> <p>Conclusions</p> <p>This article concludes a project aimed to establish the contemporary global distribution of the DVS of malaria. The three articles produced are intended as a detailed reference for scientists continuing research into the aspects of taxonomy, biology and ecology relevant to species-specific vector control. This research is particularly relevant to help unravel the complicated taxonomic status, ecology and epidemiology of the vectors of the Asia-Pacific region. All the occurrence data, predictive maps and EO-shape files generated during the production of these publications will be made available in the public domain. We hope that this will encourage data sharing to improve future iterations of the distribution maps.</p

Self-assembly of a polyrotaxane containing a cyclic &apos;&apos;bead&apos;&apos; in every structural unit in the solid state: Cucurbituril molecules threaded on a one-dimensional coordination polymer

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Molecular container assembly capable of controlling binding and release of its guest molecules: Reversible encapsulation of organic molecules in sodium ion complexed cucurbituril

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A simple construction of a rotaxane and pseudorotaxane: Syntheses and X-ray crystal structures of cucurbituril threaded on substituted spermine

A simple, one-step, high-yield synthesis of a rotaxane and pseudorotaxane based on cucurbituril and spermine is presented. Various spectroscopic techniques and X-ray diffraction methods were used to characterize the supramolecular species.open1173sciescopu

Novel low-valent zirconium porphyrin complexes: syntheses, characterization and x-ray crystal structures of (eta(5)-cyclopentadienyl)zirconium tetraphenylporphyrin and (eta(2)-diphenylacetylene)zirconium octaethylporphyrin

Reactions of (por)ZrCl2 [por = octaethylporphyrinato (oep) or tetraphenylporphyrinato (tpp) dianion] with TlCp and diphenylacetylene in the presence of Na/Hg or Mg produce novel low-valent zirconium porphyrin complexes (por)Zr(eta(5)-Cp) 1 and (por)Zr(eta(2)-PhC=CPh) 2, respectively; spectroscopic and/or structural data for 1 and 2 are consistent with a formalism in which 1 is a resonance hybrid of a zirconium(III) metal-centered radical and a zirconium(IV) porphyrin radical anion while 2 is a zirconium(II) complex stabilized by a four-electron-donor alkyne ligand.open1113sciescopu

Novel eta(1)-alkynyl zirconium porphyrin complexes: synthesis and characterization of (por)Zr(eta(1)-C CR)(3)Li(THF) [por = octaethylporphyrinato (oep) or tetraphenylporphyrinato dianion (tpp); R = Ph, SiMe3]

Reaction of (por)ZrCl2 [por = 2,3,7,8,12,13,17,18-octa-ethylporphyrinato dianion (oep) or 5,10,15,20-tetraphenylporphyrinato dianion (tpp)] with 3 equiv, of LiC=CR (R = Ph and SiMe3) produces novel alkynyl zirconium(Iv) porphyrin complexes (por)Zr(eta(1)-C=CR)(3)Li(THF) in which three alkynyl ligands are coordinated to the zirconium center in a piano stool fashion and the Li+ ion is bound to the pocket formed by three alkynyl ligands; treatment of (por)Zr(eta(1)-CECPh)(3)Li(THF) with anhydrous HCl produces a C-C bond coupled product H2C=CPh(C=CPh) and HC=CPh quantitatively.open119sciescopu

Self-assembly of interlocked structures: Rotaxanes, polyrotaxanes and molecular necklaces

Our recent work on construction of interlocked structures such as rotaxanes, polyrotaxanes and molecular necklaces using the principles of self assembly and coordination chemistry is described. In the synthesis of these structures, the barrel-shape molecule cucurbituril is used as a molecular "bead" and metal ions or metal complexes are used as "glue" or "angle connectors". Judicious choice of metal ions, counter ions and "strings" is important in order to construct the desired supramolecular structures.X1122sciescopu