A cytokinesis checkpoint requiring the yeast homologue of an APC-binding protein

Abstract

Checkpoint controls ensure that events of the cell-division cycle are completed with fidelity and in the correct order. In budding yeast with a mutation in the motor protein dynein, the mitotic spindle is often misaligned and therefore slow to enter the neck between mother cell and budding daughter cell. When this occurs, cytokinesis (division of the cytoplasm into two) is delayed until the spindle is properly positioned. Here we describe mutations that abolish this delay, indicating the existence of a new checkpoint mechanism. One mutation lies in the gene encoding the yeast homologue of EB1, a human protein that binds the adenomatous polyposis coli (APC) protein, a tumour suppressor. EB1 is located on microtubules of the mitotic spindle and is important in spindle assembly. EB1 may therefore, by associating with microtubules, contribute to the sensor mechanism that activates the checkpoint. Another mutation affects Stt4, a phosphatidylinositol-4-OH kinase. Cold temperature is an environmental stimulus that causes misalignment of the mitotic spindle in yeast and appears to activate this checkpoint mechanism.

The p21-activated Protein Kinase-related Kinase Cla4 Is a Coincidence Detector of Signaling by Cdc42 and Phosphatidylinositol 4-Phosphate

“…The checkpoint is essential for the viability of mutant cells lacking components of the dynein-dynactin complex, which have defects in spindle positioning. Therefore, inactivation of genes encoding components of this checkpoint is lethal in cells lacking dynein (65). Indeed, a partial loss of function mutation in STT4 is lethal in dynactin complex mutants (65), suggesting that the PI 4-kinase encoded by STT4 is required for checkpoint function.…”

“…Therefore, inactivation of genes encoding components of this checkpoint is lethal in cells lacking dynein (65). Indeed, a partial loss of function mutation in STT4 is lethal in dynactin complex mutants (65), suggesting that the PI 4-kinase encoded by STT4 is required for checkpoint function. However, an alternative explanation is that a spindle-positioning defect is lethal in combination with a defect in mitotic exit.…”

“…Regulation of Mitosis by Phosphatidylinositol 4-Phosphate Synthesis-PI4P synthesis has been implicated in a yeast cell cycle checkpoint that delays cell division (65). The checkpoint delays cell division until the mitotic spindle is correctly positioned along the mother-bud axis.…”

Chromosome instability in human lung cancers: possible underlying mechanisms and potential consequences in the pathogenesis

“…The C-terminal domain of APC binds to microtubules as well as to a protein called EB1. It has been shown that the EB1 protein associates at the spindle microtubules and centrosomes, and functions in the cytokinesis checkpoint (Muhua et al, 1998). Recently, APC was also suggested to play a role in kinetochore-microtubule attachment, whereas truncated mutations of APC, which eliminate microtubule binding, induce chromosomal missegregation and the CIN phenotype (Kaplan et al, 2001;Fodde et al, 2001).…”

Chromosomal localization and promoter analysis of the adenomatous polyposis coli binding protein RP1

“…During G1, microtubules in cells lacking BIM1p showed reduced dynamicity due to a slower shrinkage rate, fewer rescues and catastrophies, and more time spent in an attenuated/paused state (Tirnauer et al, 1999). A delay in the cell cycle before cytokinesis in cells with mutated EB1/RP1 homologues was observed in budding yeast as well (Muhua et al, 1998). At least in yeast, homologues of the human EB/RP protein family may be a necessary component of a new cellcycle checkpoint.…”