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

## TL;DR

This study reveals how the Pmo25 protein helps regulate cell division in fission yeast by stabilizing the contractile ring and recruiting key proteins to the division site.

## Contribution

The study identifies Pmo25's role in contractile ring stability and Sid2 localization during cytokinesis in fission yeast.

## Key findings

- Pmo25 interacts with myosin-II light chain Cdc4 and is essential for contractile ring assembly.
- Pmo25 colocalizes with and recruits the NDR kinase Sid2 to the division plane.
- Pmo25 binds to Ync13 and modulates glucanase Eng1 secretion for cell separation.

## Abstract

Mouse protein-25 (MO25) family proteins are crucial in development and morphogenesis from plants to humans. The fission yeast MO25 protein Pmo25 is essential for cell polarity and division. However, how Pmo25 regulates cytokinesis remains largely unknown. Here, we found that the actomyosin contractile ring and septum formation were defective during cytokinesis in pmo25 mutants. Pmo25 physically and genetically interacted with the myosin-II light chain Cdc4, which is essential for the contractile-ring assembly and function. Additionally, pmo25 mutations had synthetic genetic interactions with all other tested mutations in contractile-ring proteins. Moreover, Pmo25 colocalized with the NDR kinase Sid2 and participated in its recruitment to the division plane. Furthermore, Pmo25 directly bound the Munc13/UNC-13 protein Ync13 and modulated the secretion of glucanase Eng1 to the division site for daughter-cell separation. Our data provide insight into how Pmo25 regulates cytokinesis and suggest that the conserved MO25 proteins can link various steps of cytokinesis.

•The cytokinetic contractile ring and cell separation are defective in pmo25 mutants•Myosin light chain Cdc4 and the NDR kinase Sid2 may bind to Pmo25•Pmo25 is important for the recruitment of Sid2/Mob1 and Eng1 to the division site•Pmo25 directly interacts with the Munc13/UNC-13 protein Ync13

The cytokinetic contractile ring and cell separation are defective in pmo25 mutants

Myosin light chain Cdc4 and the NDR kinase Sid2 may bind to Pmo25

Pmo25 is important for the recruitment of Sid2/Mob1 and Eng1 to the division site

Pmo25 directly interacts with the Munc13/UNC-13 protein Ync13

Protein; Organizational aspects of cell biology; Protein structure aspects