Ach R A, Gruissem W
Department of Plant Biology, University of California, Berkeley 94720.
Proc Natl Acad Sci U S A. 1994 Jun 21;91(13):5863-7. doi: 10.1073/pnas.91.13.5863.
Ran is a 25-kDa Ras-related nuclear GTP-binding protein which is very highly conserved in humans, Saccharomyces cerevisiae, and Schizosaccharomyces pombe. Ran has been found to form a stable, noncovalent complex with the chromatin-associated protein RCC1, a negative regulator of mitosis. In Sch. pombe, a temperature-sensitive mutation in the RCC1 homolog encoded by the pim1 gene causes premature induction of mitosis, and this mutation can be suppressed by overexpression of the Ran homolog encoded by spi1. We report here the cloning of three Ran cDNAs from tomato. The Ran protein is very highly conserved among plants, animals, and fungi. In tomato, Ran mRNA is expressed in all tissues examined, even those with little or no cell division, indicating that Ran in plants may have functions other than just control of mitosis. We have found that the tomato Ran protein can direct a beta-glucuronidase reporter protein to the plant cell nucleus, confirming that Ran is a nuclear protein in plants. We show that the tomato Ran protein can suppress the Sch. pombe pim1 mutation, indicating that the tomato Ran protein and the Sch. pombe spi1 protein are functionally homologous.
Ran是一种25千道尔顿的与Ras相关的核GTP结合蛋白，在人类、酿酒酵母和粟酒裂殖酵母中高度保守。已发现Ran与染色质相关蛋白RCC1（一种有丝分裂的负调节因子）形成稳定的非共价复合物。在粟酒裂殖酵母中，由pim1基因编码的RCC1同源物中的温度敏感突变会导致有丝分裂的过早诱导，而这种突变可以通过由spi1编码的Ran同源物的过表达来抑制。我们在此报告从番茄中克隆出三个Ran cDNA。Ran蛋白在植物、动物和真菌中高度保守。在番茄中，Ran mRNA在所有检测的组织中都有表达，甚至在那些几乎没有或没有细胞分裂的组织中也有表达，这表明植物中的Ran可能具有除控制有丝分裂之外的其他功能。我们发现番茄Ran蛋白可以将β-葡萄糖醛酸酶报告蛋白导向植物细胞核，证实Ran在植物中是一种核蛋白。我们表明番茄Ran蛋白可以抑制粟酒裂殖酵母的pim1突变，这表明番茄Ran蛋白和粟酒裂殖酵母的spi1蛋白在功能上是同源的。
