Spindle poles

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.

Wigge, P. A., Jensen, O. N., Holmes, S., Soues, S., Mann, M., and Kilmartin, J. V. (1998). Analysis of the Saccharomyces spindle pole by matrix-assisted laser desorption/ionization (MALDI) mass spectrometry. J. Cell Biol. 141, 967-977. 

Mailer Why do you say that the first spindle poles are made of PCM Is there some reason to think that PCM is needed without a centrosome In Nenopus, I have never heard anyone argue that there is PCM organizing the meiotic spindles. If you look at the /-tubulin staining pattern, it is totally different in a meiotic spindle than in a mitotic spindle. 

Kubiak I don t know what happens to the centriole material that is brought by the sperm. What we detect at the spindle pole is a material that is reactive to y-tubulin or MPM2 antibodies. We call it PCM because the same material accompanies centrioles in other cells. All that we know is that there are plenty of these small spots in mouse oocytes also out of the spindle and that they can be gathered to opposite places with respect to the chromosomes. Moreover, as I mentioned, we have shown recently that this also happens in the absence of chromosomes (Brunet et al 1998). 

Hunt All I know is what happens in clams, because I have seen it with my own eyes you do not duplicate the spindle pole if you inhibit protein synthesis, so you get a monopolar second meiotic spindle, which causes chaos. 

Chia No, what determines fate in the daughter cells is whether or not they inherit the cell fate determinants which are normally localized as basal crescents. If the crescents of cell fate determinants are not fixed, they will not always overlie one of the spindle poles. Consequently, their segregation to the daughter cells will not always be asymmetric. 

Importantly, we observed that the two spindle poles behaved differently following spindle severing the posterior spindle pole had a higher peak velocity than the anterior one (Fig. 2). This suggests that a more extensive vector sum is... 

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). 

N-terminal methylation of proteins is possible and can play a major role in mitosis. Chen etal. discovered that the N-terminal serine or proline of regulator of chromatin condensation 1 (RCCl) is methylated. RCCl associates with chromatin, binding to histones H2 A and H2B, regulated by Ran, a GTPase. " For methylation to occur, the initiating methionine must be removed and a proline and lysine must be at positions 3 and 4, respectively. If RCCl is N-terminal methylation deficient, its binding to histones loses efficiency, which can cause spindle pole defects and ultimately cause problems in cell division. This work suggests the first known function for N-terminal protein methylation. ... 

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... 

Gaetz J, Kapoor TM (2004) Dynein/dynactin regulate metaphase spindle length by targeting depolymerizing activities to spindle poles. J Cell Biol 166 465-471... 

C. parvum is a protist related to the apicomplexans P. falciparum and Toxoplasma. P. falciparum and T gondii possess the apicoplast organelle, a remnant plastid acquired by secondary symbiosis. It has been shown that the I gondii apicoplast is segregated into daughter cells by microtubules of mitotic spindle poles (Striepen et al. 2000). As the apicoplast is in contact with the mitochondrion, it has been hypothesized that mitochondrial inheritance... 

Wu SP, Wu G, Surerus KK, Cowan JA (2002) Iron-sulfur cluster biosynthesis. Kinetic analysis of [2Fe-2S] cluster transfer from holo ISU to apo Fd role of redox chemistry and a conserved aspartate. Biochemistry 41 8876-8885 Yaffe MP, Stuurman N, Vale RD (2003) Mitochondrial positioning in fission yeast is driven by association with dynamic microtubules and mitotic spindle poles. Proc Natl Acad Sci USA 100 11424-11428... 

Microtubules, especially those that make up the mitotic spindle, are in a delicate state of balance between assembly and disassembly. This is because both the formation of the spindle and the movement of chromosomes to opposite spindle poles depend on carefully coordinated extension or shrinkage at both ends of the microtubules in the spindle. The end of a microtubule that terminates with /1-tubulin is more dynamic than the other end, which has an a-tubulin monomer as its final subunit. In cells, microtubules usually grow out from some sort of organizing... 

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