Research Topic D - Dynamics of nuclear pores and open mitosis

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Research articles

Straube, A., Enard, W., Berner, A., Wedlich-Söldner, R., Kahmann, R. & Steinberg G. (2001) A split motor domain in a cytoplasmic dynein. EMBO J., 20, 5091-5100.

A split motor domain in a cytoplasmic dynein (348Kb PDF)

Summary - In U. maydis the heavy chain of cytoplasmic dynein is encoded by two genes, which are both essential. The gene product Dyn1 contains the ATP-binding sites, whereas the microtubule binding region is provided by Dyn2. Both proteins co-localize and assemble in the cell. This appears necessary in order to function as a motor. One role of this complex is the transport of nuclei prior to mitosis. This is the first report on a split dynein heavy chain. The reason for this interesting phenomenon is not yet clear.



Straube, A., Weber, I. & Steinberg,G. (2005) A novel mechanism of nuclear envelope break-down in a fungus: Nuclear migration strips off the envelope. EMBO J., 24, 1674-1685.

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Summary - In many basidiomycete the nucleus moves into the daughter cell prior to mitosis. We show here that dynein pulls on astral microtubules in order to stretch the nucleus. After the nuclear envelope breaks at the tip, chromosomes leave the envelope, which collapses and gets recycled. Subsequently, a spindle is formed in the cytoplasm. As a dynein-dependent removal of the nuclear envelope occurs in fungi, an 'open' cytoplasmic mitosis might be an ancient process that was lost in ascomycete fungi, including the yeasts S. cerevisiae and S. pombe.



Fink, G. , Schuchardt, I., Colombelli, J., Stelzer, E. & Steinberg, G. (2006) Dynein-mediated pulling forces drive rapid mitotic spindle elongation in Ustilago maydis. EMBO J., 25, 4897-908.

Dynein-mediated pulling forces drive rapid mitotic spindle elongation in Ustilago maydis (660Kb PDF)   View movie 1   View movie 2

Summary - We demonstrate that kinesin-5 supports slow spindle elongation early in anaphase. In anaphase B dynein appears at and pulls on astral microtubules. This activity rapidly elongates the spindle and segregates the chromosomes. A role of dynein in anaphase B is not described for fungi, but found in animals. This reinforces the similarity between animals and U. maydis.



Theisen, U., Straube, A. & Steinberg, G. (2008) Dynamic rearrangement of nucleoporins during fungal 'open' mitosis, Mol. Biol. Cell, 19:1230-1240.

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Summary - We analyzed the behaviour of components of the nuclear pore complex during open mitosis of U. maydis. Similar to animal cells, the nuclear pore disassembles in prophase and reassembles in telophase. Nup107/Nup133 appears at the chromosomes in meta- and anaphase, but are not found on kinetochors. This is the first report on the dynamic behaviour in open fungal mitosis. The observed rearrangement of nucleoporins confirms the similarity between animals and U. maydis

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Anaphase B spindle in Ustilago maydis

Figure 1: Anaphase B spindle in Ustilago maydis. Rapid spindle elongation separates the chromosomes (stained by RFP-histone 4, H4). This process depends on dynein that pulls on the astral microtubules (astral MTs, stained with GFP-alpha-Tubulin, Tub1).

Nuclear envelope break down and mitosis in U

Figure 2: Nuclear envelope break down and mitosis in U. maydis. The envelope opens at the tip in pro/metaphase and a spindle is formed in the cytoplasm ('open mitosis'). Note that the scale does not correspond with duration of each mitotic stage. The graph was modified from Straube et al. 2005, EMBO J., 20, 5091.

Model of the role of kinesin-1, kinesin-3 and dynein

Figure 3: Nuclear pores (green, Nup107) and endoplasmic reticulum (red, ER-SKL) in U. maydis. Note that the pores green colocalise with the red nuclear envelope, which results in a yellow colour.