Mid2p stabilizes septin rings during cytokinesis in fission yeast.
Septins are filament-forming proteins with a conserved role in cytokinesis. In the fission yeast Schizosaccharomyces pombe, septin rings appear to be involved primarily in cell-cell separation, a late stage in cytokinesis. Here, we identified a protein Mid2p on the basis of its sequence similarity to S. pombe Mid1p, Saccharomyces cerevisiae Bud4p, and Candida albicans Int1p. Like septin mutants, mid2delta mutants had delays in cell-cell separation. mid2delta mutants were defective in septin organization but not contractile ring closure or septum formation. In wild-type cells, septins assembled first during mitosis in a single ring and during septation developed into double rings that did not contract. In mid2delta cells, septins initially assembled in a single ring but during septation appeared in the cleavage furrow, forming a washer or disc structure. FRAP studies showed that septins are stable in wild-type cells but exchange 30-fold more rapidly in mid2delta cells. Mid2p colocalized with septins and required septins for its localization. A COOH-terminal pleckstrin homology domain of Mid2p was required for its localization and function. No genetic interactions were found between mid2 and the related gene mid1. Thus, these studies identify a new factor responsible for the proper stability and function of septins during cytokinesis.
Berlin
Ana
A
Department of Microbiology, Columbia University College of Physicians and Surgeons, New York, NY 10032, USA.
Paoletti
Anne
A
Chang
Fred
F
D000595:Amino Acid Sequence; D015415:Biomarkers; D002135:Calcium-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D018797:Cell Cycle Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D005656:Fungal Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D049452:Green Fluorescent Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins / Q000378:metabolism; D008562:Membrane Glycoproteins; D008565:Membrane Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation; D017434:Protein Structure, Tertiary; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D012568:Schizosaccharomyces / Q000166:cytology / Q000235:genetics / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
D015415:Biomarkers; D002135:Calcium-Binding Proteins; D018797:Cell Cycle Proteins; D005656:Fungal Proteins; D047908:Intracellular Signaling Peptides and Proteins; D008164:Luminescent Proteins; C091625:MID2 protein, S cerevisiae; D008562:Membrane Glycoproteins; D008565:Membrane Proteins; D011993:Recombinant Fusion Proteins; D029701:Saccharomyces cerevisiae Proteins; D049452:Green Fluorescent Proteins