The mitosis-to-interphase transition is coordinated by cross talk between the SIN and MOR pathways in...

Area of Science:

• Cell biology
• Molecular and cell biology
• Cytoskeletal dynamics

Background:

• Cytoskeletal remodeling is critical for cell division, particularly during the transition from mitosis to interphase.
• In fission yeast, the MOR pathway regulates actin polarization, while the SIN pathway controls actomyosin ring assembly and cytokinesis.
• Mechanisms coordinating these pathways during cell cycle transitions remain unclear.

Purpose of the Study:

• To elucidate the regulatory relationship between the MOR and SIN signaling pathways in fission yeast.
• To understand how cytoskeletal remodeling is coordinated during the mitosis-to-interphase transition.

Main Methods:

• Investigated the interaction between the MOR and SIN pathways using fission yeast genetics.
• Focused on the role of Nak1 kinase and Orb6 in MOR pathway regulation.
• Assessed the impact of MOR pathway inhibition on SIN pathway mutants and vice versa.

Main Results:

• Demonstrated that the SIN pathway inhibits MOR signaling during mitosis by interfering with Nak1 kinase-mediated activation of Orb6.
• Showed that inactivating the MOR pathway rescues cytokinetic defects in SIN mutants.
• Found that failure to inhibit MOR signaling is toxic when the cell division apparatus is compromised.
• Observed that weakened SIN signaling can trigger ectopic cytokinesis upon MOR pathway attenuation.

Conclusions:

• Revealed a mutually antagonistic relationship between the SIN and MOR pathways in fission yeast.
• Established that this antagonism is essential for the completion of cytokinesis.
• Highlighted the importance of this regulatory crosstalk for coordinating cytoskeletal remodeling during the mitosis-to-interphase transition.