A stable microtubule bundle formed through an orchestrated multistep process controls quiescence exit

Area of Science:

• Cell Biology
• Molecular Biology
• Biophysics

Background:

• Microtubules are dynamic polymers essential for cellular functions.
• Proliferation cessation often correlates with microtubule stabilization.
• Stable microtubule structures, like the yeast nuclear bundle, play key roles in cell quiescence.

Purpose of the Study:

• To elucidate the step-by-step assembly mechanism of the quiescent yeast nuclear bundle.
• To describe the molecular players and interactions involved in microtubule structure formation and disassembly.
• To understand the entire lifecycle of a stable microtubule structure in vivo and its physiological relevance.

Main Methods:

• Characterization of a multistep assembly process.
• Investigation of Aurora B-dependent mechanisms.
• Analysis of kinesin-14, kinesin-5, and kinesin-8 roles.
• Examination of microtubule-kinetochore and kinetochore-kinetochore interactions.
• In vivo studies of microtubule dynamics during quiescence and proliferation.

Main Results:

• Detailed the original multistep process for nuclear bundle assembly in quiescent yeast.
• Identified an Aurora B-dependent mechanism with precise temporality.
• Demonstrated the sequential roles of kinesin-14 and kinesin-5 in assembly.
• Showcased the involvement of microtubule-kinetochore and kinetochore-kinetochore interactions.
• Described the cooperative disassembly process mediated by kinesin-8 upon quiescence exit.

Conclusions:

• Provided the first molecular-scale description of a stable microtubule structure's entire lifecycle in vivo.
• Established the necessity of full microtubule bundle disassembly for cell re-entry into proliferation.
• Shed light on the physiological function of this stable microtubule structure in yeast quiescence and cell cycle regulation.