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Current Biology : CB Oct 2010Little is known about how the first animals evolved from their single celled ancestors. Over 120 years ago, Haeckel proposed that animals evolved through "repeated...
Little is known about how the first animals evolved from their single celled ancestors. Over 120 years ago, Haeckel proposed that animals evolved through "repeated self-division of [a] primary cell,"[1] an idea supported by the observation that all animals develop from a single cell (the zygote) through successive rounds of cell division [2]. Nonetheless, there are multiple alternative hypotheses [3], including the formal possibility that multicellularity in the progenitor of animals occurred through cell aggregation, with embryogenesis by cell division being secondarily derived. The closest known relatives of animals, choanoflagellates, are emerging as a model system for testing specific hypotheses about animal origins [–7]. Studying colony formation in choanoflagellates may provide a context for reconstructing the evolution of animal multicellularity. We find that the transition from single cells to multicelled colonies in the choanoflagellate occurs by cell division, with sister cells remaining stably attached.
Topics: Aphidicolin; Biological Evolution; Cell Division; Cell Proliferation; Choanoflagellata; Time-Lapse Imaging
PubMed: 20971426
DOI: 10.1016/j.cub.2010.09.014 -
Proceedings of the National Academy of... Sep 2007Tipin and its interacting partner Tim1 (Timeless) form a complex at replication forks that plays an important role in the DNA damage checkpoint response. Here we...
Tipin and its interacting partner Tim1 (Timeless) form a complex at replication forks that plays an important role in the DNA damage checkpoint response. Here we identify Xenopus laevis Tipin as a substrate for cyclin E/cyclin-dependent kinases 2 that is phosphorylated in interphase and undergoes further phosphorylation upon entry into mitosis. During unperturbed DNA replication, the Tipin/Tim1 complex is bound to chromatin, and we were able to detect interactions between Tipin and the MCM helicase. Depletion of Tipin from Xenopus extracts did not significantly impair normal replication but substantially blocked the ability of stalled replication forks to recover after removal of a block imposed by aphidicolin. Tipin-depleted extracts also showed defects in the activation of Chk1 in response to aphidicolin, probably because of a failure to load the checkpoint mediator protein Claspin onto chromatin.
Topics: Adaptor Proteins, Signal Transducing; Animals; Aphidicolin; Carrier Proteins; Cell Cycle Proteins; Checkpoint Kinase 1; Chromatin; Cyclin E; Cyclin-Dependent Kinase 2; DNA Damage; DNA Replication; DNA-Binding Proteins; Enzyme Inhibitors; Ovum; Phosphorylation; Protein Kinases; S Phase; Xenopus Proteins; Xenopus laevis
PubMed: 17846426
DOI: 10.1073/pnas.0706347104 -
The Journal of Organic Chemistry Oct 2000The 8-epiaphidicolane skeleton (3) was formed in one key reaction by highly diastereoselective tandem transannular Diels-Alder (TADA)-aldol reactions from the...
The 8-epiaphidicolane skeleton (3) was formed in one key reaction by highly diastereoselective tandem transannular Diels-Alder (TADA)-aldol reactions from the trans-trans-cis trienic macrocycle (4). The unnatural derivative (11R)-(-)-8-epi-11-hydroxyaphidicolin (2) was thus constructed, and an original solution to the C16 functionalization problem of many aphidicolin (1) syntheses is presented.
Topics: Aldehydes; Aphidicolin; Crystallography, X-Ray; Enzyme Inhibitors; Indicators and Reagents; Molecular Structure
PubMed: 11031030
DOI: 10.1021/jo0007635 -
Somatic Cell Genetics Mar 1981Aphidicolin is a specific inhibitor of DNA polymerase alpha and blocks DNA synthesis in vivo. The inhibition of purified alpha-polymerase has been shown to be...
Aphidicolin is a specific inhibitor of DNA polymerase alpha and blocks DNA synthesis in vivo. The inhibition of purified alpha-polymerase has been shown to be competitive with dCTP but not with the other three deoxynucleoside triphosphates (dNTPs). In order to study the various roles that the alpha-polymerase might play in DNA replication and/or repair, we have attempted to isolate Chinese hamster V79 cells that are resistant to aphidicolin. Four resistant mutants were isolated from BrdU--black light- and UV-mutagenized cells. None of the mutants isolated contains an alpha-polymerase that is resistant, in crude extract measurements, to aphidicolin. Three mutants isolated, however, were found to be resistant to araC. Two mutants tested were found to be sensitive to cytidine and have elevated levels of dCTP or all 4 dNTPs. These results indicate that they are nucleotide pool mutants instead of alpha-polymerase mutants. One mutant, aphr-4, is characterized by the following: (1) high level of dCTP; (2) thymidine (or CdR, UdR) auxotrophic; (3) sensitive to thymidine (and AdR, GdR); (4) slow-growing; (5) cytidine sensitive; (6) UV sensitive and hypermutable at the ouabain-resistant locus; and (7) a ninefold increase in frequency of chromatid gaps and breaks when cells are exposed to BrdU-containing medium. Revertants of aphr-4 which are partially aphidicolin-resistant and retain the first three characteristics listed above, but not the others, have been isolated. The appearance of this type of revertant indicates that either aphr-4 or its "revertant" is a double mutant.
Topics: Animals; Aphidicolin; Cell Line; Clone Cells; Cricetinae; Cricetulus; Diterpenes; Drug Resistance; Lung; Mutation; Phenotype; Radiation Tolerance; Ultraviolet Rays
PubMed: 6794164
DOI: 10.1007/BF01567660 -
Cancer Chemotherapy and Pharmacology 1995The aim of this study was to examine whether resistance to cisplatin [cis-diamminedichloroplatinum (II)] (CDDP) could be overcome by amphotericin B, cyclosporin A and...
The aim of this study was to examine whether resistance to cisplatin [cis-diamminedichloroplatinum (II)] (CDDP) could be overcome by amphotericin B, cyclosporin A and aphidicolin in two sublines of human larynx carcinoma HEp2 cells. The sensitivity of parental and cisplatin-resistant CA3 and CK2 cells to amphotericin B, cyclosporin A and aphidicolin, and also the effects of these drugs (given in maximal nontoxic concentrations) on cisplatin sensitivity were determined by clonogenic survival assay. CA3 and CK2 cells were sensitive to amphotericin B, and resistant to cyclosporin A and aphidicolin, compared with their parental cells. Amphotericin B increased cisplatin toxicity 2-fold in CA3 cells and 2.7-fold in CK2 cells, while it had no effect in parental HEp2 cells. Cyclosporin A did not influence the sensitivity of examined cells to cisplatin. The sensitizing effect of aphidicolin was more obvious in cisplatin-resistant cells. Cisplatin toxicity was increased by aphidicolin: 1.5-fold in HEp2 cells, 2-fold in CA3 cells, and 1.9-fold in CK2 cells. Therefore, the resistance to cisplatin in human larynx carcinoma CA3 and CK2 cells can be partially reversed by amphotericin B and aphidicolin.
Topics: Amphotericin B; Aphidicolin; Cell Survival; Cisplatin; Cyclosporine; Drug Resistance; Humans; Laryngeal Neoplasms; Tumor Cells, Cultured; Tumor Stem Cell Assay
PubMed: 7828276
DOI: 10.1007/BF00689453 -
European Journal of Biochemistry May 1987The mode of action of aphidicolin on DNA synthesis catalysed by the DNA polymerase of Methanococcus vannielii is competitive for dCTP, noncompetitive for dATP, dGTP and...
The mode of action of aphidicolin on DNA synthesis catalysed by the DNA polymerase of Methanococcus vannielii is competitive for dCTP, noncompetitive for dATP, dGTP and dTTP and uncompetitive for activated DNA. The kinetic data are accounted for by a mechanism in which dCTP and aphidicolin compete for the dCTP-specific binding site on the DNA polymerase. The dissociation constant for the aphidicolin--DNA-polymerase complex is 0.04-0.07 microM. Similar modes of inhibition of DNA synthesis exist for DNA polymerase alpha of higher eucaryotes but not for eubacteria or viruses and suggests a close functional relationship between the DNA polymerase of eucaryotes and of the archaebacterium M. vannielii.
Topics: Aphidicolin; Binding Sites; DNA Replication; Diterpenes; Euryarchaeota; Kinetics; Nucleic Acid Synthesis Inhibitors; Protein Binding; Substrate Specificity
PubMed: 3106039
DOI: 10.1111/j.1432-1033.1987.tb11208.x -
Genomics Aug 1993The constitutive 3p14.2 fragile site is the most highly inducible fragile site in the human genome. This locus may predispose chromosome 3 to specific losses due to...
The constitutive 3p14.2 fragile site is the most highly inducible fragile site in the human genome. This locus may predispose chromosome 3 to specific losses due to deletions and translocations that have been associated with several malignancies, including hereditary renal cell carcinoma. Using aphidicolin concentrations of 0.4 and 4.0 microM, we have generated and isolated 23 and 22 respective somatic cell hybrids that contain chromosome 3 short-arm breaks. The breakpoints in these hybrids have been localized with numerous chromosome 3 markers. We have observed that at the low aphidicolin dose, chromosome-3 breaks cluster within the 3p14.2 region, whereas at the high aphidicolin dose, two new loci, one within 3p14.1 and the other near the centromere, become predominantly affected. Our studies have failed to differentiate any of the 3p14.2 breakpoints from each other or from the t(3;8)(p14.2;q24.13) familial renal cell carcinoma translocation breakpoint, suggesting that the fragile site may have played a role in the generation of this balanced translocation. The resulting somatic cell hybrids generated from this work have refined the marker localizations within 3p13-p21.1 and should facilitate the physical characterization of this interesting region.
Topics: Animals; Aphidicolin; Blotting, Southern; Chromosome Fragile Sites; Chromosome Fragility; Chromosome Mapping; Chromosomes, Human, Pair 3; Cricetinae; Cricetulus; DNA; DNA Damage; Humans; Hybrid Cells; Mutagenesis; Mutagens; Polymerase Chain Reaction
PubMed: 8406484
DOI: 10.1006/geno.1993.1330 -
Radiation Research Mar 1991The duration of the cell cycle in synchronous cultures of HeLa S3 cells that were either irradiated with 3.5 Gy of 220-kV X rays in mid-S phase or treated in early G1 or...
The duration of the cell cycle in synchronous cultures of HeLa S3 cells that were either irradiated with 3.5 Gy of 220-kV X rays in mid-S phase or treated in early G1 or mid-S phase for several hours with 1 or 3 microM aphidicolin, or were subjected to both treatments, was measured by time-lapse cinemicrography. When compared with the generation time of untreated cells, the delay in cell progression with the combined treatment was found to be less than the sum of the delays with the individual treatments, but longer than the imposed delay caused by treatment with aphidicolin alone. Because recovery from potentially lethal radiation damage proceeds in the presence of aphidicolin, this finding suggests that a portion of the radiation-induced delay in cell progression may be associated with processes other than those that directly affect cell viability. It was also observed that the incidence of both spontaneous and radiation-induced sister-cell fusion is decreased in cultures incubated in the presence of aphidicolin.
Topics: Aphidicolin; Cell Cycle; Diterpenes; HeLa Cells; Humans; S Phase
PubMed: 1900372
DOI: No ID Found -
Biochimica Et Biophysica Acta Oct 1994DNA polymerases involved in ultraviolet (UV)-induced DNA repair were studied in human fibroblasts using the inhibitors of DNA polymerases, aphidicolin which inhibits DNA...
Involvement of DNA polymerase delta and/or epsilon in joining UV-induced DNA single strand breaks in human fibroblasts (comparison of effects of butylphenyldeoxyguanosine with aphidicolin).
DNA polymerases involved in ultraviolet (UV)-induced DNA repair were studied in human fibroblasts using the inhibitors of DNA polymerases, aphidicolin which inhibits DNA polymerases alpha, delta and epsilon, and butylphenyldeoxyguanosine (BuPGdR) which inhibits DNA polymerase alpha strongly and weakly inhibits delta and epsilon. Both inhibitors inhibited replicative DNA synthesis in a dose dependent manner as measured by thymidine incorporation. However, BuPGdR did not accumulate single strand breaks in cells irradiated with 5 J/m2 UV-light even at the highest dosage tested, indicating that BuPGdR does not inhibit DNA repair. On the other hand, aphidicolin accumulated single strand breaks in UV-light irradiated cells. These results suggest that DNA polymerase delta and/or epsilon are mainly involved in UV-induced DNA repair.
Topics: Aphidicolin; DNA; DNA Polymerase II; DNA Polymerase III; DNA Repair; DNA Replication; DNA-Directed DNA Polymerase; Deoxyguanosine; Fibroblasts; Humans; In Vitro Techniques; Nucleic Acid Synthesis Inhibitors; Ultraviolet Rays
PubMed: 7918625
DOI: 10.1016/0167-4781(94)90052-3 -
Chromosome Research : An International... 2004Fragile sites are considered structural features of mammalian chromosomes and a commonly repeated hypothesis is that they are evolutionarily conserved. We tested this...
Fragile sites are considered structural features of mammalian chromosomes and a commonly repeated hypothesis is that they are evolutionarily conserved. We tested this hypothesis by establishing the subchromosomal homology of regions harbouring fragile sites in the chromosomes of humans, Macaca fascicularis (MFA) and Mandrillus sphinx (MSP). We delineated the interspecific homology of chromosome bands expressing aphidicolin-induced fragile sites of homologues to human chromosomes 1, 3, 5, 7, 18 and X by the comparative FISH of human BAC and YAC clones. Notably, two YAC clones known to span human chromosome regions containing fragile sites were shown to also span fragile sites in macaques and mandrills. The present comparative BAC/YAC mapping data represent, up to now, the most precise evidence of fragile site conservation during primate evolution.
Topics: Animals; Aphidicolin; Chromosome Fragile Sites; Chromosome Mapping; Chromosomes; Enzyme Inhibitors; Genetic Markers; Humans; In Situ Hybridization, Fluorescence; Macaca fascicularis; Mandrillus; Recombination, Genetic
PubMed: 15505403
DOI: 10.1023/B:CHRO.0000045753.88789.ea