Visualization of a Ran-GTP Gradient in Interphase and Mitotic
            <i>Xenopus</i>
            Egg Extracts

Kaláb, Petr; Weis, Karsten; Heald, Rebecca

doi:10.1126/science.1068798

Cited by 508 publications

(435 citation statements)

References 25 publications

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“…(3) shows that Ran-GTP decreases roughly exponentially with the distance (r-s) from the chromosome. The characteristic length of the Ran-GTP gradient is determined as [3,17], (4) Since the diffusivity of Ran is 20 μm 2 /s and the k I value is in the range of 0.5 -5 s -1 , the Ran-GTP gradient appears to be precipitous with the characteristic length of 2 -6 μm [6,16], as indeed was measured experimentally [8]. Similar characteristic length and nearly exponential form of the protein activity gradients were first reported for the different geometry where protein is activated at the membrane of a spherical cell and diffuses in the cell interior where it is deactivated [3].…”

Section: Spatial Gradients In Single-protein Modules Activity Gradienmentioning

confidence: 63%

“…The development of imaging techniques allowed direct experimental observation of activity gradients in the control of the mitotic spindle [6,8]. This process involves the diffusible small GTPase Ran.…”

Section: Spatial Gradients In Single-protein Modules Activity Gradienmentioning

confidence: 99%

“…With identical diffusion coefficients D for both forms of the GTPase, the stationary profile of activated GTPase c(x) is described by (5) with the specific GTP hydrolysis rate constant k I . To model the source, one can either assume a fixed concentration c 0 of active GTPase at the boundary x =0, (6) or postulate that the rate of the surface-reaction (the GEF-catalyzed activation with rate constant k A ) equals the diffusive flux: (7) For both scenarios, using a Neumann (zero flux) condition for the other system boundary at x L (8) we obtain an analytical solution of the form (9) with the gradient's characteristic length L = 1/φ (see Eq. (4)).…”

Section: Spatial Gradients In Single-protein Modules Activity Gradienmentioning

confidence: 99%

“…For instance, fluorescence resonance energy transfer-based biosensors enabled the detection of gradients of the small GTPases Cdc42 [5] and Ran [6][7][8] as well as of phosphorylated stathmin, a microtubule-binding protein [9]. With suitable probes, even highly unstable enzyme-substrate complexes can nowadays be monitored with sub-cellular spatial resolution [10].…”

Section: Introductionmentioning

confidence: 99%

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Signaling cascades as cellular devices for spatial computations

Stelling

Kholodenko

2008

J. Math. Biol.

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Signaling networks usually include protein-modification cycles. Cascades of such cycles are the backbones of multiple signaling pathways. Protein gradients emerge from the spatial separation of opposing enzymes, such as kinases and phosphatases, or guanine nucleotide exchange factors (GEFs) and GTPase activating proteins (GAPs) for GTPase cycles. We show that different diffusivities of an active protein form and an inactive form leads to spatial gradients of protein abundance in the cytoplasm. For a cascade of cycles, using a discrete approximation of the space, we derive an analytical expression for the spatial gradients and show that it converges to an exact solution with decreasing the size of the quantization. Our results facilitate quantitative analysis of the dependence of spatial gradients on the network topology and reaction kinetics. We demonstrate how different cascade designs filter and process the input information to generate precise, complex spatial guidance for multiple GTPase effector processes. Thus, protein-modification cascades may serve as devices to compute complex spatial distributions of target proteins within intracellular space.

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Section: Spatial Gradients In Single-protein Modules Activity Gradienmentioning

confidence: 63%

Section: Spatial Gradients In Single-protein Modules Activity Gradienmentioning

confidence: 99%

Section: Spatial Gradients In Single-protein Modules Activity Gradienmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Signaling cascades as cellular devices for spatial computations

Stelling

Kholodenko

2008

J. Math. Biol.

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“…Research has determined that a Ran-GTP/GDP concentration gradient exists, which is proposed to drive chromatin induced spindle assembly (Carazo-Salas et al, 1999;Kalab et al, 2002). Chromatin bound RCC1…”

Section: Figure 13 Cdk1 Activation Pathwaymentioning

confidence: 99%

An ATM- and ATR-dependent checkpoint inactivates spindle assembly by targeting CEP63

Smith¹,

Dejsuphong

Balestrini³

et al. 2009

Nat Cell Biol

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The effects of ATM and ATR signalling induced by chromosomal breakage have been described extensively in modulating cell cycle progression up to the onset of mitosis.However, DNA damage checkpoint responses in mitotic cells are not well understood.This thesis reports on the effects of double strand breaks on the progression of mitosis.We found ATM and ATR activation can occur in mitotic Xenopus laevis egg extract and the induction of ATM and ATR by chromosomal breakages inhibits spindle assembly in both Xenopus egg extract and somatic cells. The delay in mitotic progression induced by ATM and ATR was found not to involve major spindle assembly factors activities such as, Cdk1, Plx1 and RCC1/Ran-GTP. However, normal anastral spindles formation around linear DNA coated beads, which can activate ATM and ATR, linked centrosome-driven spindle assembly to ATM and ATR dependent spindle defects. cDNA expression library screening was undertaken to identify novel ATM and ATR targets in this mitotic checkpoint pathway, through which the novel centrosomal protein XCEP63 was identified as a likely candidate. Data obtained from depletion and reconstitution of XCEP63 in Xenopus egg extract established that normal centrosome-driven spindle assembly requires XCEP63. Moreover, ATM and ATR phosphorylates XCEP63 on serine 560 and promotes delocalisation from the centrosome. ATM and ATR inhibition or addition of non-phosphorylable XCEP63 recombinant protein mutated at serine 560 prevents spindle assembly abnormalities.These findings suggest that ATM and ATR regulate mitotic events by targeting XCEP63 and centrosome-dependent spindle assembly. This pathway may provide support for DNA repair processes or regulate cell survival in the presence of mitotic DNA damage. 3

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Nuclear‐Cytoplasmic Transport

McPherson

Lange

Doetsch

et al. 2009

Encyclopedia of Life Sciences

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In eukaryotic cells, the genomic deoxyribonucleic acid (DNA) in the nucleus is separated from the translational machinery in the cytoplasm by the nuclear envelope. Transport of macromolecules such as proteins and ribonucleic acid (RNA) across this membrane is essential for cellular function and requires active nuclear–cytoplasmic transport systems. These systems consist of soluble transport receptors, which recognize and bind cargo in one compartment, mediate transport through nuclear pore complexes embedded in the nuclear envelope and deliver cargo in the target compartment. Disruption of this highly regulated process results in abnormal cell function and is linked to human disease etiology. Understanding the contribution of nuclear protein and RNA transport to cellular organization is one of the major challenges in cell biology. Key Concepts Transport into and out of the nucleus occurs through nuclear pore complexes (NPCs), which are large proteinaceous channels that perforate the nuclear membrane. Proteins destined for import into the nucleus contain a nuclear localization signal (NLS) and proteins destined for export from the nucleus contain a nuclear export signal (NES), each of which targets them for transport. Soluble transport receptors called importins and exportins or karyopherins recognize and bind macromolecular cargos and facilitate transport through the nuclear pore. The asymmetric distribution of RanGDP in the cytoplasm and RanGTP in the nucleus controls the directionality of nuclear transport. Nuclear protein import can be regulated through inter‐ or intramolecular occlusion of the NLS or NES; posttranslation modification of the targeting signal; compartmental sequestration of the cargo protein or altering properties of the nuclear transport machinery including receptors and nuclear pores. Many classes of RNA are transported via Ran‐regulated, karyopherin‐dependent pathways. Messenger ribonucleic acid (mRNA) export is highly coupled to mRNA processing and is mediated by distinct receptors. Mutations in nuclear targeting signals and nuclear transport receptors have been linked to several human diseases.

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Visualization of a Ran-GTP Gradient in Interphase and Mitotic Xenopus Egg Extracts

Cited by 508 publications

References 25 publications

Signaling cascades as cellular devices for spatial computations

Signaling cascades as cellular devices for spatial computations

An ATM- and ATR-dependent checkpoint inactivates spindle assembly by targeting CEP63

Nuclear‐Cytoplasmic Transport

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