Replication and G 2 checkpoints: their response to caffeine

Pelayo, Helvia R.; Lastres, Pedro; Torre, Consuelo de la

doi:10.1007/s004250000415

Cited by 28 publications

(32 citation statements)

References 29 publications

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“…3A, left panel). Thus, caffeine or okadaic acid were unable to override the HU-induced S-phase block, which is in agreement with the results found before in onion root cells (Amino and Nagata, 1996;Pelayo et al, 2001). However, when caffeine or okadaic acid were added to the HU-blocked cells expressing CycB2-HA, the mitotic indices were raised to a level of around 50 and 25%, respectively, when compared with control cells without HU.…”

Section: Resultssupporting

confidence: 91%

“…Drugs such as caffeine or okadaic acid are known to cancel the DNA-replication checkpoint in yeast and animal cells, but were found to be ineffective in plant cells (Amino and Nagata, 1996;Pelayo et al, 2001). A reason for this could be that in plants mitotic cyclins are not expressed in S-phase-arrested cells.…”

Section: Resultsmentioning

confidence: 99%

“…Caffeine is a drug that inhibits checkpoint function in animal cells (Schlegel and Pardee, 1986;Andreassen and Margolis, 1992;Moser et al, 2000), such as the replication checkpoint during S phase (Schlegel and Pardee, 1986) and the DNA damage checkpoint in G2 phase (Blasina et al, 1999). In plants, caffeine is able to override the G2 DNA damage checkpoint (Hartley-Asp et al, 1980;González-Fernández et al, 1985) but it is unable to cancel replication checkpoints in S phase (Amino and Nagata, 1996;Pelayo et al, 2001). Okadaic acid, a protein phosphatase 2A inhibitor, induces premature mitosis in animal cells in a similar way to caffeine (Ghosh et al, 1996).…”

Section: Discussionmentioning

confidence: 99%

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A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint

Weingartner

Pelayo

Binarová

et al. 2003

Journal of Cell Science

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Mitotic progression is timely regulated by the accumulation and degradation of A- and B-type cyclins. In plants, there are three classes of A-, and two classes of B-type cyclins, but their specific roles are not known. We have generated transgenic tobacco plants in which the ectopic expression of a plant cyclin B2 gene is under the control of a tetracycline-inducible promoter. We show that the induction of cyclin B2 expression in cultured cells during G2 phase accelerates the entry into mitosis and allows cells to override the replication checkpoint induced by hydroxyurea in the simultaneous presence of caffeine or okadaic acid, drugs that are known to alleviate checkpoint control. These results indicate that in plants, a B2-type cyclin is a rate-limiting regulator for the entry into mitosis and a cyclin B2-CDK complex might be a target for checkpoint control pathways. The cyclin B2 localization and the timing of its degradation during mitosis corroborate these conclusions: cyclin B2 protein is confined to the nucleus and during mitosis it is only present during a short time window until mid prophase, but it is effectively degraded from this timepoint onwards. Although cyclin B2 is not present in cells arrested by the spindle checkpoint in metaphase, cyclin B1 is accumulating in these cells. Ectopic expression of cyclin B2 in developing plants interferes with differentiation events and specifically blocks root regeneration, indicating the importance of control mechanisms at the G2- to M-phase transition during plant developmental processes.

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Section: Resultssupporting

confidence: 91%

Section: Resultsmentioning

confidence: 99%

Section: Discussionmentioning

confidence: 99%

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A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint

Weingartner

Pelayo

Binarová

et al. 2003

Journal of Cell Science

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“…For the study, we have used synchronized populations of onion root meristematic cells, obtained by treating root meristems with hydroxyurea (HU) for 14 h. This treatment causes cells to accumulate at a cell-cycle checkpoint located between late G1 and early S phases (Young and Hodas 1964). The release of the drug and the return to normal culture conditions produces a wave of synchronized cells whose progression through the cell-cycle periods can be easily followed by taking samples at different times and analyzing them by flow cytometry (Dolezel et al 1999;Pelayo et al 2001). In these synchronous cell populations, we have described the ultrastructural alterations of the nucleolus throughout the different periods of the interphase.…”

Section: Introductionmentioning

confidence: 99%

The nucleolar structure and the activity of NopA100, a nucleolin-like protein, during the cell cycle in proliferating plant cells

González-Camacho

Medina

2005

Histochem Cell Biol

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For the purpose of gaining knowledge of the relationships between cell proliferation and ribosome biogenesis, as two fundamental mutually interconnected cellular processes, studies were performed on cell populations synchronized in their cell-cycle progression by treatment with hydroxyurea, followed by sampling at different times after its removal. A structural rearrangement of the nucleolus was observed throughout the interphase, along with changes in the relative amounts of different nucleolar subcomponents. A structural model of nucleolar organization was associated with each interphase period. Throughout interphase, the nucleolin-like protein, NopA100, was immunodetected in the dense fibrillar component of the nucleolus, preferentially near fibrillar centers and its levels were shown to increase from G1 to G2. A western blotting analysis of soluble nuclear protein extracts with anti-NopA100 antibody resulted in the intense labeling of a 100-kDa band, but also of a series of proteins related to it, suggesting that NopA100 undergoes a physiological process of proteolytic maturation, similar to that described for mammalian nucleolin, but not reported in other biological model systems. Physiological proteolysis of NopA100, related to cell-cycle progression, was confirmed after the nuclei extracted from synchronized cells were treated with the protease inhibitor, leupeptin, which resulted in an increase of the 100-kDa band at the expenses of the decrease of some other bands, according to the cell-cycle stages. We therefore conclude that there is a relationship between the increase in nucleolar activity, cell-cycle progression, nucleolar structure, the activity of NopA100, and the proteolysis of this nucleolin-like protein.

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“…Gim6nez-Abifin et al 2000). In plant cells, replication and postreplication checkpoints, such as those surveilling the completion of DNA replication and the postreplicative repair of DNA damage in G2 and prophase, are conserved (Del Campo et al 1997, Pelayo et al 2001. The existence of a spindle checkpoint that controls the metaphase-to-anaphase transition was made obvious by observations of colchicine-arrested cells which, after their delay at c-mitosis, reorganize their chromatin and re-form a nuclear envelope around the chromosomal complement (Sans et al 1989).…”

Section: Introductionmentioning

confidence: 99%

Synchronous nuclear-envelope breakdown and anaphase onset in plant multinucleate cells

et al. 2001

Self Cite

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Multinucleate plant cells with genetically balanced nuclei can be generated by inhibiting cytokinesis in sequential telophases. These cells can be used to relate the effect of changes in the distribution of nuclei in the cytoplasm to the control of the timing of cell cycle transitions. Which mitotic cell cycle events are sensitive to differences in the amount of cytoplasm surrounding each chromosomal complement has not been determined. To address this, we maximized the cell size by transiently inhibiting replication, while cell growth was not affected. The nuclei of 93% of the elongated cells reached prophase asynchronously compared to 46% of normal-sized multinucleate cells. The asynchronous prophases of normal-sized cells became synchronous at the time of nuclear-envelope breakdown, and the ensuing metaphase plate formation and anaphase onset and progression occurred synchronously. The elongated multinucleate cells were also very efficient in synchronizing the prophases at nuclear-envelope breakdown, in the prophase-to-prometaphase transition. However, 2.4% of these cells broke down the nuclear envelope asynchronously, though they became synchronous at the metaphase-to-anaphase transition. The kinetochore-microtubular cycle, responsible for coordinating the metaphase-to-anaphase transition and for the rate of sister segregation to opposite spindle poles during anaphase, remained strictly controlled and synchronous in the different mitoses of a single cell, independently of differences in the amount of cytoplasm surrounding each mitosis or its ploidy. Moreover, the degree of chromosome condensation varied considerably within the different mitotic spindles, being higher in the mitoses with the largest surrounding cytoplasm.

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Replication and G 2 checkpoints: their response to caffeine

Cited by 28 publications

References 29 publications

A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint

A plant cyclin B2 is degraded early in mitosis and its ectopic expression shortens G2-phase and alleviates the DNA-damage checkpoint

The nucleolar structure and the activity of NopA100, a nucleolin-like protein, during the cell cycle in proliferating plant cells

Synchronous nuclear-envelope breakdown and anaphase onset in plant multinucleate cells

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