Spatial and Translational Regulation of Exocyst Subunits by Cell Cycle in Budding Yeast.

BACKGROUND Previous studies have shown that exocyst complex is located at polarized growth sites at different cell cycle stages in budding yeast. But how cell cycle and the cyclin-dependent kinase, Cdk1, regulate the distribution of exocyst complex on the plasma membrane and the protein level of each exocyst subunit is not clear. MATERIAL AND METHODS Using budding yeast as a research material, regulation of cell cycle and Cdk1 on exocyst localization on the plasma membrane and on level of each exocyst subunit were examined by methods of cell biology and molecular biology. RESULTS Exocyst complex is located at growth sites on the plasma membrane in both budding and non-budding stages. Cdk1 activity is required for polarized distribution of exocyst complex in late G1, S and M phases, but not in cytokinesis stage. Cdk1 is not required for the assembly and localization of exocyst complex on plasma membrane. The protein level of Sec3 but not other exocyst subunits is regulated by the cell cycle. CONCLUSIONS Cdk1 activity is required for exocyst polarization before cytokinesis during the cell cycle progression, but not for its assembly and localization on the plasma membrane. Dynamic localization and protein level of the complex subunits are regulated by the cell cycle.