An Anillin Homologue, Mid2p, Acts during Fission Yeast Cytokinesis to Organize the Septin Ring and Promote Cell Separation

• Published in: The Journal of cell biology 2003-03, Vol.160 (7), p.1093-1103
• Main Authors: Tasto, Joseph J., Morrell, Jennifer L., Gould, Kathleen L.
• Format: Article
• Language: English
• Subjects: Actins; Actins - metabolism; Amino Acid Sequence; Amino acids; Calcium-Binding Proteins - chemistry; Calcium-Binding Proteins - genetics; Calcium-Binding Proteins - metabolism; Cell cycle; Cell Division; Cell separation; Cells; Cellular biology; Contractile Proteins; Cyclin-Dependent Kinases - genetics; Cyclin-Dependent Kinases - metabolism; Cytokines; Cytokinesis; DNA-Binding Proteins - metabolism; Fungal Proteins - chemistry; Fungal Proteins - genetics; Fungal Proteins - metabolism; Gene Deletion; Gene Expression Regulation, Fungal; Genes, Fungal; Green Fluorescent Proteins; Humans; Intracellular Signaling Peptides and Proteins; Luminescent Proteins - metabolism; Membrane Glycoproteins; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Molecular Sequence Data; Mutation; Phenotypes; Protein Structure, Tertiary; Proteins; Recombinant Fusion Proteins - metabolism; Saccharomyces cerevisiae Proteins - chemistry; Saccharomyces cerevisiae Proteins - genetics; Saccharomyces cerevisiae Proteins - metabolism; Schizosaccharomyces - cytology; Schizosaccharomyces - genetics; Schizosaccharomyces - growth & development; Schizosaccharomyces - metabolism; Septum; Sequence Homology, Amino Acid; Yeast; Yeasts
• ISSN: 0021-9525; 1540-8140
• DOI: 10.1083/jcb.200211126

Anillin is a conserved protein required for cell division. One fission yeast homologue of anillin, Mid1p, is necessary for the proper placement of the division site within the cell. Here, we identify and characterize a second fission yeast anillin homologue, Mid2p, which is not orthologous with Mid1p. Mid2p localizes as a single ring in the middle of the cell after anaphase in a septin- and actin-dependent manner and splits into two rings during septation. Mid2p colocalizes with septins, and mid2Δ cells display disorganized, diffuse septin rings and a cell separation defect similar to septin deletion strains. mid2 gene expression and protein levels fluctuate during the cell cycle in a sep1- and Skp1/Cdc53/F-box (SCF)-dependent manner, respectively, implying that Mid2p activity must be carefully regulated. Overproduction of Mid2p depolarizes cell growth and affects the organization of both the septin and actin cytoskeletons. In the presence of a nondegradable Mid2p fragment, the septin ring is stabilized and cell cycle progression is delayed. These results suggest that Mid2p influences septin ring organization at the site of cell division and its turnover might normally be required to permit septin ring disassembly.