Figure 8.

Model of Rng2 functions on CR formation and contraction. (A) Function and localization of each Rng2 domain. (B) Model depicting the roles of Rng2 in CR formation and contraction. During early mitosis, nodes appear as a broad band in the medial region of the cell, dependent on anillin Mid1. The nodes contain Rng2, formin Cdc12, and myosin II. Cdc12 forms actin nuclei in each node by cooperating with profilin Cdc3 in the cytoplasm and elongates filaments from the nuclei. Rng2 assists in the generation (nucleation and/or elongation) of filaments and simultaneously arranges them into a ring, while moving gradually from the nodes and onto the filaments. Rng2 may distribute myosin II evenly over the CR to ensure its efficient contraction. F-actin bundling by Rng2 regulates F-actin dynamics in the CR by counteracting the depolymerization/severing mediated by Adf1 for proper contraction/disassembly of the ring.