Separate roles of IQGAP Rng2p in forming and constricting theSchizosaccharomyces pombecytokinetic contractile ring

Abstract

Rng2p is required for both the normal process of contractile ring formation from precursor nodes and an alternative mechanism by which rings form from strands of actin filaments, as well as for ring constriction. Systematic analysis of domain deletion mutants establishes how the four domains of Rng2p contribute to cytokinesis.

The fission yeast cytokinetic contractile ring regulates septum shape and closure

“…The actomyosin ring is required for localization of Bgs1p into a compact band at the division site (Liu et al, 2002), and deletion of the IQ calmodulin-binding motifs from the ring component IQGAP Rng2p gives a uniform distribution of Bgs1p over the septum, in contrast to the distribution observed with wild-type, where Bgs1p is concentrated at the septum edge (Tebbs and Pollard, 2013). In mutants that contain reduced levels of the contractile ring protein Cdc15p, the ring slides along the membrane until ∼2000 Bgs1p molecules are recruited to the membrane adjacent to the ring (Arasada and Pollard, 2014).…”

“…In 41xnmt1cdc15 cells the ring slid along the long axis of the cell until ∼2000 Bgs1p molecules accumulated adjacent to the ring, and the amount of Bgs1p at the ring at the onset of constriction was ∼30% lower than in wild type (Arasada and Pollard, 2014). Rng2pΔIQ cells have reduced levels of the SIN kinase Sid2p at the division plane and an altered Bgs1p distribution compared with wild-type cells (Tebbs and Pollard, 2013). In LatA-treated cells, the Bgs1p distribution is anisotropic and, interestingly, spatial variations in growth rate correlate with Bgs and Rlc1p localization (Zhou et al, 2015).…”

“…If the ring tension has only a small effect on the rate of septation, why are constriction rates lower in Rng2p mutants that lack IQ motifs, in temperature-sensitive myo2 mutant myo2-E1 cells and in cdc12-112 cells at the restrictive temperature (Proctor et al, 2012;Tebbs and Pollard, 2013)? This might be because mutations in ring components affect septation in many ways, independently of ring tension.…”

“…This might be because mutations in ring components affect septation in many ways, independently of ring tension. Indeed, Rng2p mutations resulted in fewer molecules of Sid2p kinase (a septation initiation network kinase) in rings (Sparks et al, 1999;Tebbs and Pollard, 2013), and altered the spatial distribution of Bgs1p in the cleavage furrow (Tebbs and Pollard, 2013).…”

Pombe's thirteen – control of fission yeast cell division by the septation initiation network

“…CAR association of Sid2p requires every SIN protein to be functional (Daga et al, 2005;Guertin et al, 2000;Hou et al, 2000;Ohkura et al, 1995;Salimova et al, 2000;Sparks et al, 1999). It is also noteworthy that the IQGAP Rng2p, which is necessary for CAR assembly (Laporte et al, 2011;Padmanabhan et al, 2011;Takaine et al, 2014;Tebbs and Pollard, 2013), is localised at the SPBs in mitosis (Eng et al, 1998).…”