Wang Hongyan, Tang Xie, Balasubramanian Mohan K
Temasek Life Sciences Laboratory, National University of Singapore, Singapore 117604, Republic of Singapore.
Genetics. 2003 Aug;164(4):1323-31. doi: 10.1093/genetics/164.4.1323.
Cytokinesis is the final stage of the cell division cycle in which the mother cell is physically divided into two daughters. In recent years the fission yeast Schizosaccharomyces pombe has emerged as an attractive model organism for the study of cytokinesis, since it divides using an actomyosin ring whose constriction is coordinated with the centripetal deposition of new membranes and a division septum. The final step of cytokinesis in S. pombe requires the digestion of the primary septum to liberate two daughters. We have previously shown that the multiprotein exocyst complex is essential for this process. Here we report the isolation of rho3(+), encoding a Rho family GTPase, as a high-copy suppressor of an exocyst mutant, sec8-1. Overproduction of Rho3p also suppressed the temperature-sensitive growth phenotype observed in cells lacking Exo70p, another conserved component of the S. pombe exocyst complex. Cells deleted for rho3 arrest at higher growth temperatures with two or more nuclei and uncleaved division septa between pairs of nuclei. rho3Delta cells accumulate approximately 100-nm vesicle-like structures. These phenotypes are all similar to those observed in exocyst component mutants, consistent with a role for Rho3p in modulation of exocyst function. Taken together, our results suggest the possibility that S. pombe Rho3p regulates cell separation by modulation of exocyst function.
胞质分裂是细胞分裂周期的最后阶段，在此过程中母细胞会物理性地分裂为两个子细胞。近年来，裂殖酵母粟酒裂殖酵母已成为研究胞质分裂的一种有吸引力的模式生物，因为它通过肌动球蛋白环进行分裂，其收缩与新膜和分裂隔膜的向心沉积相协调。粟酒裂殖酵母胞质分裂的最后一步需要消化初级隔膜以释放两个子细胞。我们之前已经表明，多蛋白外泌体复合物对这一过程至关重要。在此我们报告，编码一种Rho家族GTP酶的rho3(+)被分离出来，作为外泌体突变体sec8-1的高拷贝抑制子。Rho3p的过量表达也抑制了在缺乏Exo70p（粟酒裂殖酵母外泌体复合物的另一个保守组分）的细胞中观察到的温度敏感型生长表型。缺失rho3的细胞在较高生长温度下停滞，带有两个或更多个细胞核，且细胞核之间有未切割的分裂隔膜。rho3Δ细胞积累了大约100纳米的囊泡样结构。这些表型都与在外泌体组分突变体中观察到的表型相似，这与Rho3p在调节外泌体功能中的作用一致。综上所述，我们的结果提示粟酒裂殖酵母Rho3p可能通过调节外泌体功能来调控细胞分离。
