The MO25 protein Pmo25 functions in contractile ring stability and Sid2 localization during cytokinesis

Area of Science:

• Cell Biology
• Molecular Biology
• Genetics

Background:

• Mouse protein-25 (MO25) family proteins are essential for development and morphogenesis across species.
• The fission yeast MO25 protein, Pmo25, plays a critical role in maintaining cell polarity and division.
• The precise mechanisms by which Pmo25 regulates cytokinesis are not well understood.

Purpose of the Study:

• To elucidate the role of Pmo25 in regulating cytokinesis in fission yeast.
• To identify Pmo25's interacting partners and its function in contractile ring assembly and septum formation.
• To understand how Pmo25 contributes to daughter-cell separation.

Main Methods:

• Analysis of cytokinesis defects in pmo25 mutants.
• Co-immunoprecipitation and genetic interaction assays to study Pmo25-Cdc4 interactions.
• Microscopy to observe Pmo25 localization with Sid2.
• Biochemical assays to investigate Pmo25 binding to Ync13 and its effect on Eng1 secretion.

Main Results:

• pmo25 mutants exhibited defects in actomyosin contractile ring formation and septum synthesis during cytokinesis.
• Pmo25 physically and genetically interacts with myosin-II light chain Cdc4, crucial for contractile ring function.
• pmo25 mutations showed synthetic genetic interactions with mutations in other contractile ring proteins.
• Pmo25 colocalized with the NDR kinase Sid2 at the division plane and was involved in its recruitment.
• Pmo25 directly binds Ync13, modulating glucanase Eng1 secretion for cell separation.

Conclusions:

• Pmo25 is a key regulator of fission yeast cytokinesis, impacting multiple stages including contractile ring assembly, septum formation, and cell separation.
• The findings highlight Pmo25's role in coordinating diverse aspects of the cell division process.
• Conserved MO25 proteins likely integrate various steps of cytokinesis through conserved molecular mechanisms.