The role of a spindle position checkpoint protein, Tem1, in yeast sporulation
Date Issued
2016
Date
2016
Author(s)
Liu, Yu-Chia
Abstract
In the yeast Saccharomyces cerevisiae, diploid cells enter meiosis and produce four haploid spores when fermentable sugar and nitrogen resources are limited. Several stress proteins are induced during sporulation, including Hsp26. Our laboratory has discovered that there is a Hsp26-dependent spindle checkpoint to monitor spindle formation or position, and to regulate spore formation in the budding yeast. To explore the mechanism of the Hsp26-dependent spindle checkpoint in monitoring spindle positioning, we studied Tem1, one of the Hsp26-interacting proteins. Tem1 is a critical component in the mitotic exit network (MEN) pathway, it plays a sensor for proper spindle positioning between the mother cell and the daughter bud. Since the TEM1 gene is essential, we could not use a knock-out method to explore the function of Tem1 in sporulation. We put the TEM1 gene under the control of the mitosis-specific CLB2 promoter to shut down TEM1 expression in meiosis. Interestingly, sporulation frequency was increased in the CLB2p-TEM1 cells. Meiotic time course studies showed that the increase in sporulation occurs at the step of spore formation, and similar result was obtained in the hsp26 cells. In addition, the response to benomyl treatment of the CLB2p-TEM1 mutant was the same to that of the hsp26 mutant. The phenotype of the hsp26 CLB2p-TEM1 double mutant indicated that Tem1 and Hsp26 might be involved in the same pathway of the spindle checkpoint for spore formation. Our results suggest that Tem1 may be involved in the Hsp26-dependent spindle checkpoint. According to the function of Tem1 in mitosis, Tem1 might act as a sensor in the checkpoint to monitor spindle position, and in turn control spore formation. We also investigated whether the Hsp26-dependent spindle checkpoint is functional in the cells undergoing only a single meiotic division. Because cells lacking Spo13 undergo a single meiotic division, we generated hsp26 deletion strain in the spo13 background and examined its effect on sporulation. However, the sporulation frequency of the hsp26 spo13 mutant is not increased, unlike that of the hsp26 mutant. In addition, the spo13 mutant did not display a decrease in sporulation after benomyl treatment or cold-shock treatment. These observations indicated that the spindle position checkpoint has no effect in the cells undergoing only a single meiotic division.
Subjects
Tem1
Hsp26
spindle checkpoint
meiosis
Type
thesis
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