Stepwise and cooperative assembly of a cytokinetic core complex in yeast Saccharomyces cerevisiae.

Actomyosin ring (AMR) contraction and the synthesis of extracellular material are interdependent pathways of cytokinesis in the yeast Saccharomyces cerevisiae and other eukaryotes. How these interdependent pathways are physically connected is central for understanding cytokinesis. The yeast IQGAP (Iqg1p) belongs to the conserved AMR. The F-BAR domain-containing Hof1p is member ...
of a complex that stimulates cell wall synthesis. We report on the stepwise formation of a physical connection between both proteins. 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 the MIH alter Hof1p targeting to the AMR and impair AMR contraction. Epistasis analyses of two IQG1 alleles that are incompatible with MIH formation support the existence and functional significance of a large cytokinetic core complex. We propose that the MIH acts as hinge between the AMR and the proteins involved in cell wall synthesis and membrane attachment.
J. Cell. Sci.
Date: Jun. 03, 2014
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