Separate roles of IQGAP Rng2p in forming and constricting the S. pombe cytokinetic contractile ring.

Departments of Molecular Cellular and Developmental Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103 USA Departments of Molecular Biophysics and Biochemistry, Yale University, PO Box 208103, New Haven, CT 06520-8103 USA Department of Cell Biology, Yale University, PO Box 208103, New Haven, CT 06520-8103 USA.
Eukaryotic cells require IQGAP family multi-domain adapter proteins for cytokinesis, but many questions remain about how IQGAPs contribute to the process. Here we show that fission yeast IQGAP Rng2p is required for both the normal process of contractile ring formation from precursor nodes and an alternative mechanism where rings form from strands of actin filaments. Our work adds to previous studies suggesting a role for Rng2p in node and ring formation. We demonstrate that Rng2p is also required for normal ring constriction and septum formation. Systematic analysis of domain deletion mutants established how the four domains of Rng2p contribute to cytokinesis. Contrary to a previous report, the actin binding calponin homology domain of Rng2p is not required for viability, ring formation or ring constriction. The IQ motifs are not required for ring formation but are important for ring constriction and septum formation. The GAP related domain is required for node-based ring formation. The Rng2p C-terminal domain is the only domain essential for viability. Our studies identified several distinct functions of Rng2 at multiple stages of cytokinesis.
Mol. Biol. Cell Apr. 24, 2013; 0(0); [PUBMED:23615450]
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