Cell cycle control of spindle pole body duplication and splitting by Sfi1 and Cdc31 in fission yeast.

Spindle pole biogenesis and segregation are tightly coordinated to produce a bipolar mitotic spindle. In yeasts, the spindle pole body (SPB) half-bridge composed of Sfi1 and Cdc31 duplicates to promote the biogenesis of a second SPB. Sfi1 accumulates at the half-bridge in two phases in Schizosaccharomyces pombe, from anaphase to early septation and throughout G2 phase.

C-terminal anchoring of mid1p to membranes stabilizes cytokinetic ring position in early mitosis in fission yeast.

mid1p is a key factor for the central positioning of the cytokinetic ring in Schizosaccharomyces pombe. In interphase and early mitosis, mid1p forms a medial cortical band overlying the nucleus, which may represent a landmark for cytokinetic ring assembly. It compacts before anaphase into a tight ring with other cytokinetic ring components.

Fission yeast cdc31p is a component of the half-bridge and controls SPB duplication.

The fission yeast spindle pole body (SPB) is a nucleus-associated organelle that duplicates once each cell cycle during interphase. Duplicated SPBs serve as the poles of an intranuclear mitotic spindle after their insertion into the nuclear envelope in mitosis (Ding et al., Mol.

Structural and functional effects of hydrostatic pressure on centrosomes from vertebrate cells.

In an attempt to better understand the role of centrioles in vertebrate centrosomes, hydrostatic pressure was applied to isolated centrosomes as a means to disassemble centriole microtubules. Treatments of the centrosomes were monitored by analyzing their protein composition, ultrastructure, their ability to nucleate microtubules from pure tubulin, and their capability to induce parthenogenetic development of Xenopus eggs. Moderate hydrostatic pressure (95 MPa) already affected the organization of centriole microtubules in isolated centrosomes, and also impaired microtubule nucleation.

A role for centrin 3 in centrosome reproduction.

Centrosome reproduction by duplication is essential for the bipolarity of cell division, but the molecular basis of this process is still unknown. Mutations in Saccharomyces cerevisiae CDC31 gene prevent the duplication of the spindle pole body (SPB). The product of this gene belongs to the calmodulin super-family and is concentrated at the half bridge of the SPB.

Characterization of GAPCenA, a GTPase activating protein for Rab6, part of which associates with the centrosome.

The Rab6 GTPase regulates intracellular transport at the level of the Golgi apparatus, probably in a retrograde direction. Here, we report the identification and characterization of a novel human Rab6-interacting protein named human GAPCenA (for 'GAP and centrosome-associated'). Primary sequence analysis indicates that GAPCenA displays similarities, within a central 200 amino acids domain, to both the yeast Rab GTPase activating proteins (GAPs) and to the spindle checkpoint proteins Saccharomyces cerevisiae Bub2p and Schizosaccharomyces pombe Cdc16p.

gamma-Tubulin in mammalian cells: the centrosomal and the cytosolic forms.

The centrosome is one of the cellular organelles for which the mechanism by which it operates still remains to be unlavelled. The finding of the association with the centrosome of gamma-tubulin, a protein which belongs to the tubulin superfamily, has provided a long sought after biochemical tool with which to address centrosome function. We have generated a specific anti-gamma-tubulin polyclonal antibody to study the biochemical properties and the cellular distribution of the human lymphoblastic gamma-tubulin.

A high molecular weight centrosomal protein of mammalian cells is antigenically related to myosin II.

Available data on the molecular composition of the centrosome, the typical microtubule-organizing center of animal cells, are still fragmentary. To address this important issue we have taken advantage of centrosome isolation from a human lymphoblastic cell line (KE37) to generate a monoclonal antibody (mAb) library. Here we present the characterization of one of these mAbs (CTR56).

An helicoidal structure surrounding the cilium axoneme: visualization by the monoclonal antibody CC-248.

Monoclonal antibody CC-248 labels cilia differentially on Triton X-100 permeabilized ciliated epithelium of quail oviduct by indirect immunofluorescence. On isolated ciliated cells, a punctuated staining is seen at the distal region over the bend of cilia. Electron micrographs of immunoperoxidase and immunogold techniques showed that the punctuated fluorescence corresponds to a helical disposition of CC-248 antigenic sites.

Microtubular spindle and centrosome structures during the cell cycle in a dinoflagellate Crypthecodinium cohnii B.: an immunocytochemical study.

In order to determine if a mitotic spindle organizing center is present in dinoflagellate cells, we used a library of 12 monoclonal antibodies obtained by immunizing mice with isolated human centrosomes. When tested by immunofluorescence on cryosections of the dinoflaggelate Crypthecodinium cohnii B., a positive labeling was obtained with three of these antibodies.

Myosin at the apical pole of ciliated epithelial cells as revealed by a monoclonal antibody.

A monoclonal antibody (CC-212), obtained in a fusion experiment in which basal bodies from quail oviduct were used as immunogen, has been shown to label the apical pole of ciliated cells and to react with a 200-kD protein. This monoclonal antibody was demonstrated to be an anti-myosin from smooth muscle or from nonmuscular cells using the following criteria: On Western blots it reacted with the myosin heavy chains from gizzard and platelet extracts and from cultured cell line extracts, but did not react with striated muscle myosin heavy chains. By immunofluorescence it decorated the stress fibers of well-spread cells with a characteristic striated pattern, while it did not react with myotubes containing organized myofibrils.

A protein of 175,000 daltons associated with striated rootlets in ciliated epithelia, as revealed by a monoclonal antibody.

Basal bodies from laying quail oviduct were semipurified and used as immunogen to produce monoclonal antibodies. On 38 clones obtained and among those staining the apical pole of the ciliated cell, CC-310 was chosen because it labeled the apical region with a punctuated aspect, suggesting a staining of basal bodies or of basal body-associated structures; the basal pole was also labeled. The ultrastructural localization performed by the immunogold technique showed that the labeling was mainly associated with the striated rootlets.