Spindle pole bodies

Fig. 2.3 The development of polarity and asymmetric division in Saccharomyces cerevisiae. The diagram is reproduced in a slightly simplified form from the work of Lew Reed (1995) with the permission of Current Opinion in Genetics and Development, (a) The F-actin cytoskeleton strands = actin cables ( ) cortical actin patches, (b) The polarity of growth is indicated by the direction of the arrows (arrows in many directions signifies isotropic growth), (c) 10-nm filaments which are assembled to form a ring at the neck between mother and bud. (d) Construction of the cap at the pre-bud site. Notice that the proteins of the cap become dispersed at the apical/isotropic switch, first over the whole surface of the bud, then more widely. Finally, secretion becomes refocussed at the neck in time for cytokinesis, (e) The status and distribution of the nucleus and microtubules of the spindle. Notice how the spindle pole body ( ) plays an important part in orientation of the mitotic spindle.

Fig. 2.6 The moqjhological events of sporulation in Saccharomyces cerevisiae. (a) starved cell V, vacuole LG, lipid granule ER, endoplasmic reticulum CW, cell wall M, mitochondrion S, spindle pole SM, spindle microtubules N, nucleus NO, nucleolus, (b) Synaptonemal complex (SX) and development of polycomplex body (PB) along with division of spindle pole body in (c). (d) First meiotic division which is completed in (e). (f) Prepararation for meiosis II. (g) Enlargement of prospore wall, culminating in enclosure of separate haploid nuclei (h). (i) Spore coat (SC) materials produced and deposited, giving rise to the distinct outer spore coat (OSC) seen in the completed spores of the mature ascus (j). Reproduced from the review by Dickinson (1988) with permission from Blackwell Science Ltd.

As a positive control, an Spc42p (a major component of the spindle pole body) can be GFP-tagged. To accomplish this, the Spc42-GFP KanMX6 PCR product needs to be generated (Janke et al, 2004 Knop et al, 1999). 

In the filamentous fungus, Aspergillus nidulans, NIMA (never in mitosis, gene A) kinase phosphorylates H3 at Ser-10 [48]. At mitosis NIMA kinase association with chromatin increases and following metaphase NIMA locates to the mitotic spindle and spindle pole bodies. A human NIMA-related kinase (Nek6) was identified as a putative mitotic HI and H3 kinase [49]. 

Mayer TU, Braun T, Jentsch, S (1998) Role of the proteasome in membrane extraction of a short-lived ER-transmembrane protein. EMBO ] 17 3251-3257 McCracken AA, Brodsky JL (1996) Assembly of ER-associated protein degradation in vitro dependence on cytosol, calnexin, and ATP. J Cell Biol 132 291-298 McDonald HB, Byers B (1997) A proteasome cap subunit required for spindle pole body duplication in yeast. J Cell Biol 137 539-553 McGee TP, Cheng HH, Kumagai H, Omura S, Simoni RD (1996) Degradation of 3-hydroxy-3-methylg utaryl-CoA reductase in endoplasmic reticulum membranes is accelerated as a result of increased susceptibility to proteolysis. J Biol Chem 271 25630-25638... 

S. cerevisiae shows a rather unique cell cycle with the doubling of the spindle pole body and the formation of a short mitotic spindle already in the S-phase.The G2 phase is missing. On the other hand, the cell cycle of Sch. pombe resembles the higher eukaryotes with a characteristic Gi, S, G2 and mitose phase [196]. 

The new concept of the Urediniomycetes, Ustilaginomycetes and Hymenomycetes can also be corroborated by ultrastructural data on septa and spindle pole body morphology [325, 335,336 and references cited therein also see Hibbett and Thom, 337],... 

Other characters that generally corroborate the Urediniomycetes are the 5S rRNA secondary structure of type A [236], plate-like spindle pole bodies, the cell wall monosaccharide pattern (table 1) and simple septa tapering towards the pore or poreless septa [22, 217, 234, 335, 336, 340, 343-348]. The members of this class are predominantly dimorphic except the Uredinales... 

Yoder TJ, McElwain MA, Francis SE, Bagley J, MnUer EG, Pak B, O Toole ET, Winey M, Davis TN. Analysis of a spindle pole body mntant reveals a defect in biorientation and illnminates spindle forces. Mol. Biol. Cell 2005 16 141-152. 

The mitotic apparatus is basic to mitosis in all organisms, but its appearance and components can vary widely. In the budding yeast Saccharomyces cerevisiae, for instance, the mitotic apparatus consists of just a spindle, which itself is constructed from a minimal number of kinetochore and polar microtubules. These microtubules are organized by spindle pole bodies, trilamlnated structures located In the nuclear membrane, which do not break down during mitosis. Furthermore, because a yeast cell is small, It does not require well-developed asters to assist in mitosis. Although the spindle pole body and centrosome differ structurally, they have proteins such as 7-tubulin In common that act to organize the mitotic spindle. Like yeast cells, most plant cells do not contain visible centrosomes. We consider the unique features of the mitotic apparatus In plant cells at the end of this section. 

Palazzo, R. E., and T. N. Davis. 2001. Centrosomes and spindle pole bodies. Methods in Cell Biology, vol. 67. Academic Press. 

Pereira, G., and E. Schiebel. 2001. The role of the yeast spindle pole body and the mammalian centrosome in regulating late mitotic events. Curr Opin. Cell Biol. 13 762-769. 

Lauze, E. Stoelcker, B. Luca, F.C. Weiss, E. Schutz, A.R. Winey, M. Yeast spindle pole body duplication gene MPSl encodes an essential dual specificity protein kinase. EMBO J., 14, 1655-1663 (1995)... 

Figure 1.1. Complex two-hybrid interaction networks. Two-hybrid interaction networks for proteins related to spindle pole body (A) and vesicular transport (B) are shown. Allows indicate two-hybrid interactions, beginning from the bait and ending at the prey. Double-headed allows mean that the interactions were detected bidirectionally. Note that arrows indicate the direction of two-hybrid interactions but not any biological orientation. Solid lines indicate known interactions recorded in the Yeast Proteome Database (14) but not yet detected by our two-hybrid screening [Refs in 45].

Spindle pole bodies from Saccharomyces cerevisiae are the microtubule organizing centers of yeast and are involved in all aspects of cell division. In collaboration with E. Bullitt, masses of yeast spindle pole bodies are being determined to see if different size classes correspond to distinct masses. The largest spindle pole bodies have mass of several gigadaltons. Two micrographs of freeze-dried spindle pole bodies with microtubules attached are shown in Fig. 6B. 

Fig. 6 Dark-field electron micrographs of freeze-dried specimens, (A) Yeast nuclear pore complexes full-scale is 1.024 /urn (in collaboration with Qing Yang and Christopher Akey. Boston University). (B). Yeast spindle pole bodies with microtubules attached full-scale is 2,048 /xm (in collaboration with Esther Bullitt, Boston University).

Fig. 1.10. The yeast nucleus (Williamson, 1991). SPB = Spindle pole body NUC = Nucleolus = Pore CHR = Chromatin CT = Continuous tubules DCT = Discontinuous tubules CTM = Cytoplasmic microtubules...

Fig. 1.13. Meiosis in S. cerevisiae (Tuite and Oliver, 1991). SPB = spindle pole body DB = dense body SC = synaptonemal complexes, (a) Cell before meiosis (b) dividing of SPB (c) synaptonemal complexes appear (d) separation of the SPB (e) constitution of spindle (metaphase I of meiosis) (f) dividing of the SPB (g) metaphase, n of meiosis (h) end of meiosis formation of ascospores...

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