Biomedical subjects

Gislene Pereira

Publications and source records attributed to Gislene Pereira.

7 recordsLinked to original sources

PubMed2005

Kin4 kinase delays mitotic exit in response to spindle alignment defects.

For many polarized cells, it is critical that the mitotic spindle becomes positioned relative to the polarity axis. This is especially important in yeast, where the site of cytokinesis is predetermined. The spindle position checkpoint (SPOC) therefore delays mitotic exit of cells with a mispositioned spindle. One component of the SPOC is the Bub2-Bfa1 complex, an inhibitor of the mitotic exit network (MEN). Here, we show that the Kin4 kinase is a component of the SPOC and as such is essential to delay cell cycle progression of cells with a misaligned spindle. When spindles are correctly oriented, Kin4 and Bub2-Bfa1 are asymmetrically localized to opposite spindle pole bodies (SPBs). Bub2-Bfa1 then becomes inhibited by Cdc5 polo kinase with anaphase onset, a prerequisite for mitotic exit. In response to spindle misalignment, Kin4 and Bub2-Bfa1 are brought together at both SPBs. Kin4 now maintains Bub2-Bfa1 activity by counteracting Cdc5, thereby inhibiting mitotic exit.

Cell Cycle↗

PubMed2004

Yeast centrin Cdc31 is linked to the nuclear mRNA export machinery.

Centrins are calmodulin-like proteins that function in the duplication of microtubule-organizing centres. Here we describe a new function of the yeast centrin Cdc31. We show that overproduction of a sequence, termed CID, in the carboxy-terminal domain of the nuclear export factor Sac3 titrates Cdc31, causing a dominant-lethal phenotype and a block in spindle pole body (SPB) duplication. Under normal conditions, the CID motif recruits Cdc31 and Sus1 (a subunit of the SAGA transcription complex) to the Sac3-Thp1 complex, which functions in mRNA export together with specific nucleoporins at the nuclear basket. A previously reported cdc31 temperature-sensitive allele, which is neither defective in SPB duplication nor Kic1 kinase activation, induces mRNA export defects. Thus, Cdc31 has an unexpected link to the mRNA export machinery.

Active Transport, Cell Nucleus↗

PubMed2004

Cdc14 phosphatase resolves the rDNA segregation delay.

Sister chromatid segregation in anaphase of mitosis is initiated through cleavage of cohesin by the protease separase. Two studies now show that this view is valid for most chromosomal DNA, but not for the highly repetitive ribosomal DNA (rDNA) and telomeres. The disjunction of these regions of the chromosome occurs in mid-anaphase, long after cohesin cleavage, and is regulated by the conserved phosphatase Cdc14.

Anaphase↗

PubMed2003

Separase regulates INCENP-Aurora B anaphase spindle function through Cdc14.

The inner centromere-like protein (INCENP) forms a complex with the evolutionarily conserved family of Aurora Bkinases. The INCENP-Aurora complex helps coordinate chromosome segregation, spindle behavior, and cytokinesis during mitosis. INCENP-Aurora associates with kinetochores in metaphase and with spindle microtubules in anaphase, yet the trigger for this abrupt transfer is unknown. Here we show that the conserved phosphatase Cdc14 regulated the yeast INCENP-Aurora complex, Sli15-Ipl1. Cdc14 dephosphorylated Sli15 and thereby directed the complex to spindles. Activation of Cdc14 by separase was sufficient for Sli15 dephosphorylation and relocalization. Cdc14 not only regulates mitotic exit but also modulates spindle midzone assembly through Sli15-Ipl1.

Anaphase↗

PubMed2003

The XMAP215 homologue Stu2 at yeast spindle pole bodies regulates microtubule dynamics and anchorage.

The yeast protein Stu2 belongs to the XMAP215 family of conserved microtubule-binding proteins which regulate microtubule plus end dynamics. XMAP215-related proteins also bind to centrosomes and spindle pole bodies (SPBs) through proteins like the mammalian transforming acidic coiled coil protein TACC or the yeast Spc72. We show that yeast Spc72 has two distinct domains involved in microtubule organization. The essential 100 N-terminal amino acids of Spc72 interact directly with the gamma-tubulin complex, and an adjacent non-essential domain of Spc72 mediates binding to Stu2. Through these domains, Spc72 brings Stu2 and the gamma-tubulin complex together into a single complex. Manipulation of Spc72-Stu2 interaction at SPBs compromises the anchorage of astral microtubules at the SPB and surprisingly also influences the dynamics of microtubule plus ends. Permanently tethering Stu2 to SPBs by fusing it to a version of Spc72 that lacks the Stu2-binding site in part complements these defects in a manner which is dependent upon the microtubule-binding domain of Stu2. Thus, the SPB-associated Spc72-Stu2 complex plays a key role in regulating microtubule properties.

Genotype↗

PubMed2002

Regulation of the Bfa1p-Bub2p complex at spindle pole bodies by the cell cycle phosphatase Cdc14p.

The budding yeast mitotic exit network (MEN) is a GTPase-driven signal transduction cascade that controls the release of the phosphatase Cdc14p from the nucleolus in anaphase and thereby drives mitotic exit. We show that Cdc14p is partially released from the nucleolus in early anaphase independent of the action of the MEN components Cdc15p, Dbf2p, and Tem1p. Upon release, Cdc14p binds to the spindle pole body (SPB) via association with the Bfa1p-Bub2p GTPase activating protein complex, which is known to regulate the activity of the G protein Tem1p. Cdc14p also interacts with this GTPase. The association of the MEN component Mob1p with the SPB acts as a marker of MEN activation. The simultaneous binding of Cdc14p and Mob1p to the SPB in early anaphase suggests that Cdc14p initially activates the MEN. In a second, later step, which coincides with mitotic exit, Cdc14p reactivates the Bfa1p-Bub2p complex by dephosphorylating Bfa1p. This inactivates the MEN and displaces Mob1p from SPBs. These data indicate that Cdc14p activates the MEN in early anaphase but later inactivates it through Bfa1p dephosphorylation and so restricts MEN activity to a short period in anaphase.

Anaphase↗

PubMed2002

Evidence that the Ipl1-Sli15 (Aurora kinase-INCENP) complex promotes chromosome bi-orientation by altering kinetochore-spindle pole connections.

How sister kinetochores attach to microtubules from opposite spindle poles during mitosis (bi-orientation) remains poorly understood. In yeast, the ortholog of the Aurora B-INCENP protein kinase complex (Ipl1-Sli15) may have a role in this crucial process, because it is necessary to prevent attachment of sister kinetochores to microtubules from the same spindle pole. We investigated IPL1 function in cells that cannot replicate their chromosomes but nevertheless duplicate their spindle pole bodies (SPBs). Kinetochores detach from old SPBs and reattach to old and new SPBs with equal frequency in IPL1+ cells, but remain attached to old SPBs in ipl1 mutants. This raises the possibility that Ipl1-Sli15 facilitates bi-orientation by promoting turnover of kinetochore-SPB connections until traction of sister kinetochores toward opposite spindle poles creates tension in the surrounding chromatin.

Aurora Kinases↗