Stepwise and cooperative assembly of a cytokinetic core complex in budding yeast Saccharomyces cerevisiae
FacultiesFakultät für Naturwissenschaften
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Actomyosin ring (AMR) contraction and the synthesis of extracellular material are interdependent pathways of cytokinesis in yeast Saccharomyces cerevisiae and other eukaryotes. How these interdependent pathways are physically connected is central for understanding cytokinesis. IQGAP proteins are organizers of the contractile actin myosin ring (AMR) during cytokinesis in many eukaryotic cells. Genetic evidence suggests that the yeast IQGAP (Iqg1p) that is part of the conserved AMR carries out additional roles during cytokinesis whose molecular underpinnings are not understood. Here I identified the stepwise formation of a physical connection between Iqg1p and the F-BAR protein Hof1p, a member of a complex that stimulates cell wall synthesis. The C-terminal IQ-repeats of Iqg1p first bind to the essential myosin light chain before both proteins assemble with Hof1p into the Mlc1p-Iqg1p-Hof1p bridge (MIH). Mutations in Iqg1p that disrupt this complex alter Hof1p targeting to the AMR and impair AMR contraction. Epistasis analysis of MIH-interfering iqg1 alleles that are incompatible with MIH formation supports the existence and functional significance of a large cytokinetic core complex, consisting of at least seven proteins that are stepwise assembled: Myosin light chain, Iqg1p, Myosin heavy chain, Hof1p, Chitin synthase, Inn1p, Cyk3p and Sho1p. I propose that the MIH connects the AMR with proteins involved in cell wall synthesis and membrane attachment to coordinate their activities.
Original publicationJournal of Cell Science
Subject HeadingsZellkinetik [GND]
Protein interactions [LCSH]