Tem1 localization to the spindle pole bodies is essential for mitotic exit and impairs spindle checkpoint function

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• The mitotic exit network (MEN) regulates the inactivation of cyclin-dependent kinases, enabling cell cycle progression from mitosis.
• The GTPase Tem1, localized to spindle pole bodies (SPBs), initiates MEN signaling but is inhibited by Bfa1-Bub2 until anaphase.
• Bfa1-Bub2 also function in the spindle position checkpoint (SPOC), ensuring correct spindle alignment before mitotic exit.

Purpose of the Study:

• To investigate the essential role of Tem1 localization dynamics in the proper functioning of the MEN and SPOC.
• To reevaluate the interdependent localization of Tem1, Bfa1, and Bub2.
• To establish Tem1's SPB localization as a prerequisite for mitotic exit.

Main Methods:

• Analysis of Tem1 localization dynamics on SPBs.
• Investigation of MEN component recruitment to SPBs.
• Examination of the interdependence between Tem1, Bfa1, and Bub2 localization.

Main Results:

• Tem1 loading dynamics onto SPBs dictate the recruitment of other MEN components.
• Removal of Tem1 from SPBs is critical for SPOC-mediated cell cycle arrest.
• Tem1 localization to SPBs is demonstrated as a requirement for initiating mitotic exit.

Conclusions:

• Precise regulation of Tem1 localization to SPBs is fundamental for both MEN signaling and SPOC surveillance.
• The study clarifies the interdependence of key proteins involved in cell cycle regulation.
• Tem1's SPB localization is a critical checkpoint for successful mitotic exit.