Eng K, Naqvi N I, Wong K C, Balasubramanian M K
Cell Division Laboratory, Institute of Molecular Agrobiology, National University of Singapore.
Curr Biol. 1998 May 21;8(11):611-21. doi: 10.1016/s0960-9822(98)70248-9.
An actomyosin-based contractile ring plays a pivotal role in cytokinesis. Despite the identification of many components of the ring, the steps involved in its assembly are unknown. The fission yeast Schizosaccharomyces pombe is an attractive organism in which to study cytokinesis because its cell cycle has been well characterized; it divides by medial fission using an actomyosin ring; and a number of S. pombe mutants defective in actomyosin ring assembly have been isolated. Here, we have characterized one such mutant, rng2.
Temperature-sensitive rng2 mutants accumulated F-actin cables in the medial region of the cell but failed to organize the cables into a ring. In rng2-null mutants, only a spot-like structure containing F-actin was detected. The rng2+ gene encodes a protein related to human IQGAP1, a protein that binds actin and calmodulin and is a potential effector for the Rho family of GTPases. Rng2p localized to the actomyosin ring and to the spindle pole body (SPB) of interphase and mitotic cells. Localization of Rng2p to the actomyosin ring but not the SPB required F-actin. Rng2p interacted with calmodulin, a component of the SPB and the actomyosin ring. The rng2 gene showed genetic interactions with three other actomyosin ring assembly mutants, cdc4, cdc12, and rng5.
The S. pombe IQGAP-related protein Rng2p is a component of the actomyosin ring and the SPB and is required for actomyosin ring construction following assembly of F-actin at the division site.
基于肌动球蛋白的收缩环在胞质分裂中起关键作用。尽管已鉴定出该环的许多组成成分，但其组装所涉及的步骤仍不清楚。裂殖酵母粟酒裂殖酵母是研究胞质分裂的一种有吸引力的生物体，因为其细胞周期已得到充分表征；它通过使用肌动球蛋白环进行中间分裂；并且已经分离出一些肌动球蛋白环组装有缺陷的粟酒裂殖酵母突变体。在此，我们对其中一个这样的突变体rng2进行了表征。
温度敏感型rng2突变体在细胞中间区域积累了F-肌动蛋白丝，但未能将这些丝组织成环。在rng2基因缺失突变体中，仅检测到一个含有F-肌动蛋白的点状结构。rng2+基因编码一种与人类IQGAP1相关的蛋白质，IQGAP1是一种结合肌动蛋白和钙调蛋白的蛋白质，并且是Rho家族GTP酶的潜在效应器。Rng2p定位于肌动球蛋白环以及间期和有丝分裂细胞的纺锤极体（SPB）。Rng2p定位于肌动球蛋白环而非SPB需要F-肌动蛋白。Rng2p与钙调蛋白相互作用，钙调蛋白是SPB和肌动球蛋白环的一个组成成分。rng2基因与其他三个肌动球蛋白环组装突变体cdc4、cdc12和rng5表现出遗传相互作用。
粟酒裂殖酵母IQGAP相关蛋白Rng2p是肌动球蛋白环和SPB的一个组成成分，并且在分裂位点组装F-肌动蛋白后构建肌动球蛋白环是必需的。
