MAPK-dependent control of mitotic progression in S. pombe

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Mitogen-activated protein kinases (MAPKs) are crucial for cell homeostasis, mediating adaptive responses to environmental stress.
• The mitotic checkpoint prevents aneuploidy by inhibiting mitotic exit when chromosome capture is defective.
• The precise mechanisms by which stress impacts mitotic progression remain largely unknown.

Purpose of the Study:

• To investigate the role of MAPK Pmk1 in regulating mitotic exit under stress conditions.
• To elucidate how Pmk1 influences the mitotic checkpoint and cell cycle progression.

Main Methods:

• Utilized Schizosaccharomyces pombe as a model organism.
• Performed epistasis analysis to determine the genetic interactions of Pmk1 with spindle assembly checkpoint (SAC) components.
• Investigated protein-protein interactions between Pmk1 and Cdc20Slp1 using biochemical assays.
• Analyzed the degradation of Cdc20Slp1 in stressed cells using proteasome inhibition and genetic manipulation.

Main Results:

• Pmk1-deficient cells exhibit hypersensitivity to microtubule damage and defects in metaphase arrest.
• Pmk1 is involved in maintaining spindle assembly checkpoint (SAC) signaling.
• Pmk1 physically interacts with Cdc20Slp1, an activator of the anaphase-promoting complex (APC/C).
• Cdc20Slp1 is rapidly degraded in stressed cells via a proteasome-dependent mechanism requiring Pmk1 activity and Mad3, delaying mitotic exit.

Conclusions:

• MAPK Pmk1 has a novel function in preventing premature mitotic exit and cytokinesis activation in response to stress.
• Regulation of Cdc20Slp1 turnover by Pmk1 is a key mechanism for adjusting mitotic exit timing relative to environmental conditions.