The fission yeast Chs2 protein interacts with the type-II myosin Myo3p and is required for the integrity of the actomyosin ring

In Schizosaccharomyces pombe cytokinesis requires the function of a contractile actomyosin ring. Fission yeast Chs2p is a transmembrane protein structurally similar to chitin synthases that lacks such enzymatic activity. Chs2p localisation and assembly into a ring that contracts during division requires the general system for polarised secretion, some components of the actomyosin ring, and an active septation initiation network. Chs2p interacts physically with the type-II myosin Myo3p revealing a physical link between the plasma membrane and the ring. In chs2 mutants, actomyosin ring integrity is compromised during the last stages of contraction and it remains longer in the midzone. In synchronous cultures, chs2 cells exhibit a delay in septation with respect to the control strain. All these results show that Chs2p participates in the correct functioning of the medial ring.